https://ascconline.org RSS feeds for American Society of Concrete Contractors 60 https://ascconline.org/Home/News/articleType/ArticleView/articleId/458/Guidance-for-Concrete-Contractors-29#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=458 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=458&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/458/Guidance-for-Concrete-Contractors-29 Jim Klinger, Concrete Construction Specialist The Voice Newsletter June 2024 Full disclosure: I received a call a few days ago from a former co-worker who is nearing retirement. Both of us started working concrete construction in the 1970's We spent some quality time on the phone looking back on our years in this tough business of ours. We talked as old men do. We first met on a large public works job in 1992, one of ASCC member Conco's first major projects as a GC in our market. At that time, Matt Gonsalves (1930-2018) was one of the original founders of the Conco Cement Company--and also its President. One thing that stayed with us both over the years is the set of rules Matt established--and lived by--whilst building a wildly successful concrete construction company along with his son--current President--Steve Gonsalves. One way or another, almost every single column or magazine article I write falls back somehow to Matt's Rules. What you are about to read in the ASCC Hotline call account below is a fine example. "Matt's Rules for Success" "Be safe. This is the prime directive. Safety pays". "Have fun. If you aren't having fun, find another business." "Make money. That's why we do what we do." "Keep the money you just got done making." "You always have to try to position yourself to get lucky." "The harder you work...the luckier you get." "Sometimes you have to eat a mile of excrement. But once you got it eaten...baby, you got it made." __________________________________________________________________ Question: We are attempting to wrap up the reinforced concrete portion of an affordable housing apartment complex featuring an elevated post-tensioned (PT) concrete slab one lift above street level at the so-called "podium" level. The podium slab serves as the foundation platform for 7 stories worth of wood "stick framed" construction above. Since affordable housing is a scarce commodity here in our real estate market, the project was fast-tracked by the City (including construction financing) and advertised for bid without project specifications. The only documents our estimators had to work with at bid time were the Level 3 D-D (design development) set of structural and architectural drawings, the geotechnical report, and a preliminary project schedule. This project is typical of hundreds of such podium structures we have built over the years: 50,000 square foot (SF) footprint, 36-inch-thick foundation mat, and either cast-in-place (CIP) concrete or shotcrete basement walls supporting an elevated PT slab at grade (e.g. street level) and another elevated PT podium slab one lift above grade. Late last fall, the jobsite was excavated 3 feet wide of the building footprint by the earthwork subcontractor--who sloped the bank sides back to allow our crews safe access all the way around the building to erect, strip and patch the perimeter basement walls. Because our company has such a familiarity with the typical structural framing of a podium-type reinforced concrete structure, we were very comfortable pricing the work despite being furnished incomplete construction documents. We also knew that our two competitors for this same project were working from the same D-D documents. In other words, we were bidding on a level playing field. Unfortunately, once our contract was signed, the playing field tilted...and things started rolling south from there. While it is true that we had ample experience with the concrete scope of work, we had zero experience with our customer--the general contractor (GC)--or their fresh-out-of-school project engineer assigned to oversee our concrete scope of work. The construction sequence was partially dictated by the design team. Once the first lift of perimeter CIP walls supporting the street-level PT slab was completed, the designers required the entire street-level slab to be placed, stressed, and up to full strength before application of outside wall face waterproofing--and subsequent backfilling to grade shortly thereafter--could safely begin. And therein lies our problem. Part of our standard scope of work includes patching of the formed faces of our concrete walls. This task must be completed before the follow-on waterproofer can install his work. Our standard operating procedure is to send our patch crew right behind the stripping crew--same day--which is what we did on this job. The patching was completed in late February. Due to seasonal monsoon rains, all earthwork operations were delayed--including the backfill behind the perimeter CIP walls. The GC informed us the waterproofing installation activities were going to be on rain delay as well. In the meantime, we recently completed the podium slab and submitted our final progress billing--along with a request for partial release (50 percent) of our retention as well. Instead of receiving payment, the GC has just put us on notice that we are in danger of delaying the project. The waterproofer had mobilized, examined the perimeter wall surfaces, and announced to the GC that they refused to start installation until the concrete wall surface substrate had been prepared to their satisfaction. The GC is telling the project Owner that the waterproofing manufacturer will not provide the warranty if their product is installed over the existing concrete substrate. We reminded the GC that our patching was completed months ago consistent with the formed surface tolerance requirements of concrete industry standard ACI 117-10: Specification for Tolerances for Concrete Construction and Materials. In response, the GC sent us a copy of a generic "waterproofing at exterior wall detail" from the architectural drawings and rejected our argument as follows: "Your subcontract is not based upon CIP (cast-in-place) tolerances. Nor is there any reference to that in the contract. The contract is based upon the approved plans that were given to you...please see attached detail to finish your scope of work...prompt action is required so that there are no further delays". We are confident we are doing the right thing here, and that our work already meets the contract quality requirements and was completed in a timely manner. Is there anything the ASCC Hotline can offer to help support our position? Answer: The GC's project engineer was quite correct...until he got it wrong, that is. In order for the ASCC Technical Division to get to the bottom of this one, we first need to recognize there were some serious miscues on this project--on both sides of the aisle--which occurred even before you got to project Day 1. Let's look at those miscues first. While it is true that your bid proposal letter states plain as day that your price quote is based on incomplete construction documents (e.g. no specifications), there is no evidence of follow-up on your part during the negotiation of your contract scope of work (aka "Exhibit "B"). Exhibit B is a significant section of the contract document where the quality expectations for the finished product must be clearly spelled out. In other words, anyone who reads your contract must understand straightaway what you owe the project. When we examined your Exhibit B, we found it silent on all matters related to concrete quality. Another booby trap we found is the following clause in your contract that is a classic set-up gambit for the Owner's rep to raid your pocketbook at will: Any time you see a "to the satisfaction of" clause in contract language (or in a specification section) it should serve as a red flag warning for you to grab your red pen and strike the clause from the document before signing. While this particular contract clause is not referenced in any of your project correspondence we reviewed, it is still there--waiting to be discovered--perhaps during discovery should things on your project head further south. Another significant miscue on the part of all of the contractors (that includes concrete, waterproofing, and GC) is that there was no preconstruction tolerance coordination meeting--a mandatory requirement specified in ACI-117--where quality expectations at hand-off from one trade to the next must be discussed among all stakeholders and agreed to. Such meetings in advance of the work are essential to ensuring a successful project. Knowing the above, we can now rinse out the evidence and determine what you really owe the project. When your GC tells you that "your contract is not based on CIP tolerances,” the casual observer might just be inclined to agree, since there is no explicit mention of ACI 117 (or ACI 301, for that matter) anywhere in the construction documents. This is unusual to the degree that almost all projects we review here at the ASCC Technical Division feature specifications drawn from AIA Masterspec, which appears in contract specification documents typically as: In the cases where AIA Masterspec is used, references to ACI 117 tolerances are either explicitly stated as above or such references are given within the ACI 301 document. Either way, you are covered. Unfortunately, since your project is one of the few that has proceeded without benefit of reference documents (or specifications at all), we must search elsewhere to find what tolerances you owe the project. The answer lies hidden within your structural drawing "General Notes" --in the "Project Information" section that identifies the basis of the structural design.  According to ACI 318-19: Building Code Requirements for Structural Concrete, section 26.2.1 requires the construction documents to identify the "Name and year of issue of the Code, general building code, and any supplement governing design.” In your case, the general building code listed is the 2019 edition of the California Building Code (CBC). When you signed your contract in June 2023, the 2019 CBC had already been superseded by the 2022 edition, where we find the following in Chapter 19: In plain language, what this means is that if the designers did not specify any tolerances for the structural reinforced concrete scope in their construction documents, then by default the tolerances specified in ACI 117 automatically kick in. As you can see, this is a code requirement, not only in the CBC but in the International Building Code (IBC) as well. __________________________________________________________________ Lesson learned #1: No matter what your bid proposal qualifications state, what you will be held to two years down the road from contract signing is the contract language itself. Lesson learned #2: Remember the words of former ASCC Technical Director Bruce Suprenant: "Would you like to read your contract language before you sign, or would you like the opposing attorney to read it to you two years from now in deposition?" Lesson learned #3: Never start work on a project before attending the mandatory tolerance coordination meeting specified in ACI 117-10 section 1.1.3 thusly: It is in mandatory meetings such as this that important documents such as ASCC Position Statement #27: Formed Surface Requirements for Waterproofed Walls should be reviewed and discussed among the stakeholders. Lesson learned #4: Become familiar with what reference documents are and how to handle them to protect yourself from unfair (and costly) risk. A good place to start is the article from which the above AIA Masterspec excerpt is taken, namely "ACI Reference Specifications: Consensus standards are designed for use in construction contract documents" by Bruce Suprenant, Concrete International, October 2019.  Lesson learned #5: Based on our Hotline call, a set of contract specifications (aka "project Manual") was never issued to the ASCC concrete contractor, which is consistent with the contract language excerpted above. It appears that the stakeholders on the Owner's side of the aisle did not consider such a document "applicable". This forces the concrete contractor to have a heightened awareness of risks associated with not only his work, but with all contiguous follow-on work as well. What follows is an example from a totally different project that illustrates the simple fact that there is money to be saved (or made) by opening up the project specifications and taking a peek at what is contained in the other guy's playbook. You always want to know what the other guy owes the project. This is one sure way to position yourself to get lucky. An ASCC contractor reported a Hotline case very similar to that described above. The concrete had long been placed, and the contractor's retention request was returned with a substantial backcharge attached to it. This was a massive reinforced concrete parking garage, which featured a follow-on painted surface on all "exposed" concrete that could be seen when viewed from outside the structure. We are talking any beam sides, beam bottoms, parapet (crash) walls, columns, shear walls, and so on. If you could see it, it was fair game for paint. This was not an "architectural concrete" scope per se, but all stakeholders on the project knew before bid day that the architectural color renderings clearly showed the viewable, painted concrete surfaces and understood the architect's intent. After the final concrete "catch-up" work (e.g. curbs, pads) was complete, the concrete contractor dispatched a crew to sweep each and every floor--even though not every bit of debris that ended up in the dustpan was generated by the concrete scope. The agreement was that the structure would be left "broom clean". Upon completion of this final contract scope activity, the architect, GC, and concrete contractor attended a final job walk. The architect and GC complimented the ASCC concrete contractor on another job well-done. Fast-forward six months. Since retention payment was contingent on all other portions of the project being complete, retention checks were on the near horizon. The painter was one of the last subcontractors to perform work on the jobsite. By that time, the familiar GC onsite management staff had all been transferred to other projects. Most of the jobsite trailers were gone, and the GC imported someone from another project to herd-dog the final punchlist items and close the job out. At some time during the painter's work, complaints were made to the new GC rep that the painter was having to perform undue surface preparation before the paint could be applied. Disputed items included removal of efflorescence due to seasonal monsoon rains, minor amounts of mortar leakage at beam-column connections, and so on. The painter convinced the new GC onsite rep the "extra work" was legitimate, and--between the two of them--documentation and cost tracking for backcharge purposes began in earnest. The concrete contractor was never called to discuss the disputed surface preparation claims. The ASCC member called the Hotline, wondering how on earth a structure that had been complimented by both the architect and GC a few months earlier could now be such a disaster for the follow-on painter. That is when the Hotline took a look at the other guy's playbook (aka the Division 9 specifications). Here is what we found that clearly spelled out the surface preparation scope that the painter owed the project all along: As you can discern plain as day, neither the painter nor the new GC onsite rep had any idea that section 3.03 existed--or what it contained. Unfortunately, ignorance of what is contained in construction documents (and their reference documents) seems like a costly, unforgivable epidemic in the construction industry today. (N.B. Some may argue that the painter's estimator read section 3.03 (above) and excluded such surface preparation from their Division 9 scope of work. If that was the case, where was that work transferred? By all rights, it was the GC's responsibility at bid time to find a home for the surface preparation, and to advise the new owner of that scope so it could be incorporated--and priced. No such notice of scope transfer was ever given to the ASCC member at bid time. As it turned out, we were given an opportunity later to view the paint subcontractor's Exbibit B, which did not mention exclusion of the section 3.03 surface preparation work. (No question-the painter owned surface preparation as specified.) In our experience, it is highly advisable for the concrete estimator to grab the specifications during bid time and perform what we refer to as an "oddball run.” This is where we look at the odd-numbered specifications only, starting with Division 1 (General Requirements), then division 3 (Concrete), then division 5 (Metals), then division 7 (Waterproofing), then division 9 (Finishes), and then...all the way at the back of the book...division 31 (Earthwork). By this time, the estimator should know the job well enough to determine if performing such a potential risk review in other playbook divisions is warranted. rzuellig Mon, 03 Jun 2024 17:41:00 GMT f1397696-738c-4295-afcd-943feb885714:458 https://ascconline.org/Home/News/articleType/ArticleView/articleId/454/Lean-Construction#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=454 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=454&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/454/Lean-Construction Dave MacNeel, Principal and Lean Coach, On Point Lean Consulting The Voice Newsletter June 2024 In lieu of Technical Director Mike Hernandez's article, this month we present an article from Dave MacNeel, Principal and Lean Coach, On Point Lean Consulting. His firm, On Point Lean Consulting, coaches general contractors and specialty trade contractors to apply Lean principles and tools in the field. Prior to consulting, Dave spent 20 years in operations with Baker Concrete Construction. Dave will be speaking at this year's Concrete Executive Leadership Forum, July 18-21 in Stowe, VT on "Leveraging Lean Construction for Enhanced Efficiency and Profitability. For more information, click here.  Lean Construction offers significant opportunities to the concrete construction industry.  I have seen robust implementations deliver 80% fewer injuries, 30% faster completion, and 20% lower cost.  If these numbers sound appealing, then read on. However, recognize that Lean Construction doesn't come fast, easy, or without considerable effort. Lean Construction focuses on impeccable planning and coordination by mastering these three key components:  Deeply engaging craft supervisors Eliminating waste and rework Driving continuous improvement Most construction companies make plans, communicate, watch costs, and try to avoid making the same mistake twice. But how can companies consistently deliver world-class results?  Eliminating waste is the primary answer. In 2004, the Construction Industry Institute (CII) studied manufacturing versus construction and found that manufacturing, on average, wastes 12% of its energy and effort while construction wastes 57%.  While it is painful to see this statistic, it is not all that surprising – especially since we never build the same project twice. The Lean Construction Institute developed The Last Planner System of Production Control® (LPS) to attack waste and variation. Engagement The system has several tools to attack variation and poor handoffs – starting with Phase Pull Planning. Upstream activities are ‘pulled’ by downstream work and interim completion milestones. The site team analyzes a project's intricacies and secures reliable commitments from each other about workflows and durations and what is needed for a satisfactory hand-off. Weekly planning begins once the project is pull-planned collaboratively. In the weekly coordination sessions, the project team looks at several items, including a six-week look ahead plan, to ensure the work is ‘made ready’ in advance. Trade supervisors collaborate on detailed, day-by-day plans for the coming work week. Aside from confirming what will be done and when, there are two additional elements: constraint removal and workable backlog. Constraint removal involves finding and removing any roadblocks that could derail the plan.  Examples include missing information or resources.  These potential roadblocks are assigned to individuals with a mission to remove the constraint by a specific date. ‘Workable Backlog’ is any work that could be performed but is not part of the production plan. This contingency work would be initiated if the main plan gets derailed or if the planned work is completed early, which is often the case on Lean projects.   For concrete contractors, remember that the rebar and other materials must also be available. Supervisors become engaged and take ownership when their thoughts and opinions and sought out and heard. Therefore, they must be included in discussions of schedule, methods, logistics, site utilization, materials, and equipment. If supervisors are involved in planning, they generally will do everything possible to make that plan happen. So, set goals to beat industry averages by 5%, 10%, or even 20%. Then, as work gets closer to being performed, flesh out the details by phase and with the people who will be performing the work. Eliminating Waste Stockpiling excess materials and running at full throttle every minute is rarely the best way to eliminate waste. In fact, it often causes waste on a project. Material stockpiles can be damaged by weather, stolen, or made obsolete by a design revision.  Excess materials can lead to double and triple handling and interfere with other activities. In our rush to get things done and overcome poor drawings or upstream delays, we sometimes overburden our craft workers with undue overtime. Crews rarely complain because it is good money. However, studies show enormous productivity losses and higher accident rates are associated with extended overtime. Learning & Continuous Improvement Growing a company’s knowledge base is much more than simply not making the same mistake twice. It involves continuous improvement through deeply reflecting on problems and determining the root cause. When this step is taken, the proper countermeasure can be implemented, which reduces the possibility of recurrence. In The Last Planner System, production variances are analyzed to learn collectively about how and why there was a variance and to explore options to prevent it from happening again. Some Caveats A company's biggest mistake is thinking, "We already do all this!"  Much like safety, Lean Construction is a never-ending journey to improve operational efficiency. Start small - use pilot projects to learn and create in-house ‘Lean Champions’ to drive the effort. Get proper coaching to accelerate learning the principles and applying the tools. Like a golfer who improves with coaching and dedicated practice, a company can improve its operations through engagement, waste elimination, and continuous improvement. Lean Construction requires total commitment from both executives and project supervision. This system has been shown to work repeatedly, but only when a firm develops discipline and sticks with it. Most companies have some elements of Lean in their operations.  However, very few have all of the elements together as a system, and even fewer practice every day in a consistent manner.   The good news is that any serious effort in these areas will make the firm better than when it started.  Just know that utilizing all of the elements together as a production system will yield the maximum benefit. rzuellig Mon, 03 Jun 2024 17:13:00 GMT f1397696-738c-4295-afcd-943feb885714:454 https://ascconline.org/Home/News/articleType/ArticleView/articleId/450/Guidance-for-Concrete-Contractors-28#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=450 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=450&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/450/Guidance-for-Concrete-Contractors-28 Jim Klinger, Concrete Construction Specialist The Voice Newsletter May 2024 Question: We are estimating a mid-rise, pump-place-finish only job (P-P-F) that bids roughly 2 months from now. The base building structure is framed in steel, featuring seismic frame columns founded on a network of pile caps and connecting grade beams. The slab on grade (SOG) has a footprint of 44,585 square feet (SF). The SOMD total trowel finish quantity is 254,926 SF on 6 floors, including the roof. We figured we would assume 12 each pumped concrete placements of 350 cubic yards (CY) each on floor slab areas averaging 21,000 SF each. The total SOMD quantity of 3000 psi normal weight concrete (NWC) is estimated at 4208 CY. This is a private, mixed-use medical research facility with flatness and levelness "F-numbers" specified at most slabs, including elevated slabs on metal deck (flatness only at SOMD). According to the Instruction to Bidders (ITB), the building has been fully leased and so the tenants are known, but the end uses of each floor space are still unsettled. One example that was floated to all bidders was a slab on grade envisioned as a large kitchen with tiled floor, servicing an employee cafeteria space with an exposed polished concrete look. On the other hand, the ground floor might be used as office space, with a cubicle farm that supports laboratories on the floors above. In other words, all stakeholders know going in that the final tenant improvement (TI) scope is a moving target. We have been directed to bid an assumed baseline of F-numbers, with Owner acknowledgment that there are likely to be additive change orders once the TI scope finally gets locked in. If you really want to know the truth about it all, we are not thrilled with either the project Ownership or the general contractor (GC). This is based on previous unsavory experiences involving back-charge disputes and collecting retention in a fair and timely manner. But times being what they are, we made the business decision to bite the bullet and quote the work anyway. On the last job, we worked with this same owner and GC, disputes arose with a follow-on flooring subcontractor who couldn't get a grip on the concept that the as-built top elevation of finished concrete slab surfaces can potentially--and normally--change with time. Thanks to ASCC Position Statement #6 (and a mind-numbing number of job site meetings), we were finally able to spit the hook and avoid back charges after the Owner agreed to cover any flooring contractor substrate adjustment costs. Truth be told--part of the difficulties we experienced can be attributed to our own project team having a limited grip on the quality and tolerance requirements that govern our finishing scope--let alone the contents of the contract itself. From a business standpoint, such an internal breakdown in communication and lack of situational awareness is both unacceptable and unsustainable. After that project closed out, we dropped back and did what we should have done in the first place, which is to read and fully comprehend the project contract floor finishing specifications themselves and the relevant industry documents from which they were drawn (e.g. ACI 117-10 Tolerances, ACI 302.1R-15 Guide to Concrete Floor and Slab Construction, and so on). Thanks to 20-20 hindsight, we now appreciate the value of the required preconstruction tolerance coordination meeting(s) specified in the mandatory language in ACI 117-10 section 1.1.3 as follows: So now here we are, preparing to bid on an entirely new project. We want to make sure that that between our written bid proposal qualification letter and the mandatory preconstruction tolerance coordination meeting described above that all stakeholders--including our field personnel-- understand how and why the finished concrete slab surfaces are likely to behave throughout the project (and beyond)--and who bears the burden of paying for any "no-fault" substrate adjustments as outlined by ASCC in Position Statement #6. In. other words, we are clear now on how to handle "no-fault" substrate adjustments based on the guidance in ASCC Position Statement #6. But what are the protocols when "no-fault" becomes "yes-fault" (e.g. when our finishing crew fails to meet the required F-numbers)? During our in-house, retroactive due diligence exercise, we noticed in the Dipstick Operator's Manual prepared by the FACE company a sample random traffic floor flatness/levelness specification that presents several options to remedy out-of-tolerance finish work: remove and replace, grinding, and skim coating. We also noticed a fourth option, which involves giving the Owner a credit to compensate for non-complying work as described here: What can the Hotline tell us about option #4--the rebate? Answer: ASCC Position Statement #6 is one of the most used--therefore one of the most valuable--documents in the ASCC Hotline technical library. This document is the result of a successful collaboration effort conducted among ASCC and many of the follow-on flooring trades with whom costly back-charge disputes typically arise. The message contained in Position Statement #6 is that the apparent trade "incompatibility" is actually a "no-fault" phenomenon to the extent that neither concrete contractors nor follow-on flooring contractors are able to control the technical reasons for the inevitable changes in concrete floor top surface contours over time e.g. curling and slab deflection. After the draft document was prepared and floated to the follow-on trade representatives for review, the end result was their endorsement and permission to use their brand logos on our Position Statement cover sheet as shown below: Taken as a stand-alone document, ASCC members have been able to convince GC's and Owners at various stages of a project (from pre-bid RFI's to unfortunate disputes many months after a slab has been placed and finished) that the right thing to do is for the Owner to fund potential slab surface adjustments via an allowance line item carried in the Owner's budget. Sometimes, however, the background that drives Position Statement #6 may need to be submitted upstream to Owners, GC's and designers--along with the document itself--for educational purposes. Fair enough request. The best document we have found that presents the complete back story and technical rationale that supports Position Statement #6 and is aimed at all concrete construction stakeholders can be found at the Construction Specifier by using this link. Written by ASCC Hotline operators emeritus Ward Malisch and Bruce Suprenant, the article titled "Bridging the Specification Gap between Divisions 03 and 09: Concrete and Floorcovering Associations Unite" takes the reader on a step-by-step, easy-to-understand tour described by the authors as follows: "Division 03 specifies concrete floor surface flatness requirements to be installed by the concrete contractor. Division 09 specifies the concrete floor surface flatness for the flooring installer that must be met before installing the floorcovering. What does it mean when these requirements are incompatible?" "The Owner does not want a specification battle; he or she just needs a concrete slab that allows the floorcovering to be installed to achieve a good appearance and obtain the manufacturer's warranty. Clearly, there must be a cost-effective and efficient solution. Cooperation among the American Society of Concrete Contractors (ASCC) and six associations has led to a solution for bridging the specification gap between Divisions 03 and 09." We recommend this article be attached to every copy of ASCC Position Statement #6 that our members send upstream--for whatever reason. So the above takes care of everything you want to know about the "no-fault" scenario. But what about the "yes-fault" situation, particularly the "rebate" method of making the Owner whole when the concrete finish work is non-compliant? Crediting money back to the Owner via deductive change orders (or retention adjustment) as a remedy for non-conforming work is nothing new. But here at the Hotline, we have only heard of a few cases where the concrete contractor has admitted to such a commercial arrangement for not meeting the floor tolerance requirements. Usually, we hear about the first 3 options e.g. remove and replace, grind, or skimcoat. We do know that the rebate option is mentioned twice in ACI 117-10 Specification for Tolerances for Concrete Construction and Materials. This option--albeit called "liquidated damages" in the Commentary--appears in sections R4.8.4 and R4.8.5.2 as follows below:           Commentary section R4.8.4 In addition to the rebate example suggested in the FACE sample specification described above, we found an example of a similar rebate scenario in a 1996 article by Eldon Tipping titled "Using the F-Number System to manage Floor Installations" as shown below: The key to either way of calculating "rebate" or "liquidated damages" dollars is making sure the agreement is in writing before the work starts and that the credit unit rate passes your in-house reasonableness test. The FACE example suggests a credit unit of 50 cents per SF. The Tipping example suggests a credit unit of 5 cents per square foot. Depending on the floor section size and your local market cost of place-and-finish labor you carry in your estimates, both numbers could make sense when weighed against the cost of a potential, unknown back-charge at some time out in the future. (N.B: neither the FACE nor the Tipping examples show us an example calculation-- and description of any backup--that one presumes would have to be submitted to an Owner for review before a rebate arrangement could be inked. If you are viewing this through the lens of the Owner, what would you need to see before you agreed to a unit rate intended to make acceptance of substandard work product palatable?) __________________________________________________________________ Input Needed--Rubbed Finishes Update Over the past 50 years, there has been much confusion about what constitutes a rubbed finish and how such a finish is mocked up, reviewed, and eventually accepted by the customer. In addition, concrete curing specifications requiring forms to be left in place for 3 to 7 days--and a trend toward stronger concrete mixtures--have made rubbing so-called "green" concrete difficult to near impossible. We want to illustrate ASCC contractor concerns with rubbed finishes with a focus on specifications, costs, and durability. (N.B.: The term "green" in this context refers to early-age, freshly hardened concrete, say between 24 to 48 hours after placement.) The goal here is to prepare an article regarding rubbed finish "best practices" with a possible Position Statement to follow. To make that happen, we need input from concrete contractors. In January 2020, we asked VOICE readers to send us their experiences with rubbed finishes. Unfortunately, all of us were sidetracked by more pressing issues. Now things are starting to settle down a bit, and we want to focus on back-burner items. Here's some background and an update: Examples of Rubbed Finish--Past and Present 1970: A project specification called for a rubbed finish applied with a silicon carbide (aka "carborundum") brick on an exposed concrete wall for a county jail in Illinois. The nominal specified wall concrete strength was 3000 psi at 28 days, and the forms were removed the day after placement. At that time, fins were removed and the wall was rubbed, creating enough paste from the green concrete to cover bugholes and fin removal lines. 2015: A project specification required a rubbed finish on the soffit of an elevated post-tensioned (PT) concrete parking deck in Houston, Texas. The specified PT slab concrete strength was 5000 psi at 28 days (nominal), with a requirement for high-early strength of 3500 psi at 3 days to allow PT to be stressed. On day 4, the concrete in place was too strong to receive a rubbed finish. As a result, fins and offsets were addressed with a hand-held grinder, and bugholes had to be filled with additional grout before the surface was sacked. The compressive strength of the "green" concrete when rubbed in 1970 was probably on the order of 500 psi, while the concrete rubbed in 2015 was (in theory) at least 3500 psi. There is clearly a significant difference in procedures and cost in rubbing 500 psi concrete and trying to rub (and probably hand-grinding) 3500 psi material. We need to convey these differences and impacts to designers, specifiers, and other industry stakeholders. ACI 301 Specifications After conducting a literature survey of relevant industry documents, we found rubbed finishes have been specified in ACI 301 Specifications for Concrete Construction since 1960 in various forms-- including "smooth rubbed finish.” "sand floated finish.” "grout cleaned finish,” and "cork floated finish.” The 1972 specification discontinued the sand-floated finish. The 1996 specification added that a smooth, rubbed finish was to be accomplished after the period required for curing by leaving the forms in place. Early versions of the specification stated that a smooth rubbed finish was to be produced on "green" or "freshly hardened" concrete. The 2005 version of ACI 301 stated "...produce finish on hardened concrete no later than the day following formwork removal...Use no cement grout other than cement paste drawn from the concrete itself by the rubbing process.” This creates a conflict with specifications requiring form removal at 3 to 7 days since the concrete will be too hard to draw paste from the surface. The rub finish then escalates to grinding the fins and offsets and adding grout and then sacking. This rub to a grind/sack scenario creates a changed condition that is rarely recognized and paid for. Thus the concrete contractor gets left holding the sack and absorbing the cost. Now jump forward another 15 years to 2020...The latest version--ACI 301-20--specifies rubbed finish as follows: In our opinion, section 5.3.3.3 should be adjusted to make it consistent with other sections of the ACI 301 document that require specifiers to clearly designate the scope of work in Contract Documents. The operative words here are "designate" or "designated"--terms used some 50 times throughout the ACI 301-20 version. (Example: in ACI 301-20 section 6.1.1, the requirement for the architectural concrete scope is specified as follows: "This section covers construction requirements for concrete designated as architectural concrete in Contract Documents.”) We suggest the following suggested revisions be brought to the attention of ACI Committee 301 for consideration: In section 5.3.3.3, revise to read "Provide a rubbed finish in the areas designated in the Contract Documents". We also suggest this revision also be incorporated into the Mandatory Requirements Checklist section 5.3.3.3 as follows: "Designate portions of the Work to receive a rubbed finish". Based on the above (and as discussed in the latest ASCC Technical Committee meeting), we are looking for feedback from contractor members as follows: What are your experiences with rubbing concrete surfaces? Can you send us examples of bizarre or conflicting specifications? Can you provide relative cost information on any rubbing work or rework? How was rubbing handled if it was not specified in your specs? What are your best practices for rubbing concrete? Please send your feedback via email to jklinger@ascconline.org rzuellig Wed, 01 May 2024 17:56:00 GMT f1397696-738c-4295-afcd-943feb885714:450 https://ascconline.org/Home/News/articleType/ArticleView/articleId/445/Exploring-the-Potential-of-Nano-Silica-and-Colloidal-Silica-in-Enhancing-Low-Carbon-Concrete-Finishing#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=445 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=445&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/445/Exploring-the-Potential-of-Nano-Silica-and-Colloidal-Silica-in-Enhancing-Low-Carbon-Concrete-Finishing Mike Hernandez, Technical Director There has been much discussion about the challenges associated with mixes with high water demand, which can be a side effect of some high blaine I/II and IL cement, manufactured sands, and SCMs. Because of this higher water demand, early moisture loss has become more of an issue with these mixes. To keep the water inside the mix, most members have reported a substantial increase in the use of “con-film type” evaporation retarders. This class of products is not intended to be a “finishing aid” and shouldn’t be troweled into the surface after application. Applying more water to the surface is a worse general practice. At each ACI Convention in San Francisco, Boston, and New Orleans, as well as elsewhere, people are advocating for nano silica or colloidal silica either in surface applied as a true finishing aid or as an admixture. Reports include improved finishability in the plastic concrete, with little or no need for curing compound, and improved surface abrasion resistance in the hardened concrete. The feedback I have received is nearly 100% positive when using these products. The only complaint I have heard was from a ready-mix producer who said one admixture was too expensive to be economically viable. I leave the $/sf or $/cy and risk analysis to the user. The potential costs associated with a poorly finished slab and an unhappy customer are hard to quantify, but they are real. It is the policy of ASCC to avoid endorsing products so please consider this an open topic of discussion to the ASCC community. So far, the list of products I have found in this space are: Nano silica surface applied finishing and curing aid: GreenIce by Green Umbrella Day1 by Solomon Colors TK-Slab Assist RTU by TK Products Slab Armor by ChemMasters Nano silica admixtures Master X-Seed by Master Builders Solutions E5 Internal Cure and E5 Liquid Fly Ash by Specification Products We welcome your feedback on the pros and cons of these products. Please tell me your thoughts at: mhernandez@ascconline.org rzuellig Wed, 01 May 2024 17:50:00 GMT f1397696-738c-4295-afcd-943feb885714:445 https://ascconline.org/Home/News/articleType/ArticleView/articleId/437/Guidance-for-Concrete-Contractors-27#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=437 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=437&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/437/Guidance-for-Concrete-Contractors-27 Jim Klinger, Concrete Construction Specialist The Voice Newsletter March 2024 "I heard it...I heard it...I heard it on the X..." ______________________________________________________________________________ Full Disclosure (back story):  Every so often, the ASCC Hotline receives calls for assistance regarding concrete that is resistant to elevated temperatures (aka "refractory" concrete), but these inquiries have generally been limited to domestic fireplace and pizza oven-type terrestrial applications. Upon further review, there may be ASCC VOICE readers that might wish to know more about the extreme--and exotic--uses of such refractory concrete. For those curious members...you are in for a treat. __________________________________________________________________ During the initial test launch of the "Starship" vehicle from its SpaceX home base in Boca Chica, Texas, a good chunk of the reinforced concrete launch pad infrastructure--referred to by SpaceX as "Stage 0"--was blown to smithereens by the exhaust plume generated by its stage 1 cluster of 33 "Raptor2" rocket engines capable of kicking out some 16 million total pounds of thrust. Slabs, grade beams, drilled piers--the whole 9 yards--were pulverized, as depicted in the photo below. One "Business Insider" headline reported " Starship's first liftoff toward space created the equivalent of a volcanic eruption in the launchpad, physicist finds". The Los Angeles Times reported the initial test launch of the world's most powerful rocket "blasted concrete up to 6.5 miles away". When you watch video footage that documents the April 20 2023 launch (use link to one such video, below), pay attention to the large chunks of debris splashing into the nearby Gulf waters--way out past the third breaker--on the right side of your screen.        "Stage 0" launch platform at Boca Chica. Photo credit: the platform called "X".        Photo credit: Steve Clark/ Brownsville Herald (Texas). At T-plus 4:04 minutes after the last of the Starship stack cleared the tower, the trajectory of the launch vehicle veered off course, requiring a destruct command to be given to abort the mission.  The Federal Aviation Administration (FAA) declared the event a "mishap", and stated "the Starship broke up, resulting in the loss of the launch vehicle."  But a Tweet posted by SpaceX just after the "mishap" romanced it another way:  "As if the flight test was not exciting enough, Starship experienced a rapid unscheduled disassembly before stage separation". (N.B. SpaceX considered the initial test to be a resounding success, since all they really wanted to do is get the super-heavy rocket stack to clear the tower. The voice of Mission Control said at the time that anything after that "was icing on the cake.") The FAA immediately grounded SpaceX, since the launch license was valid for one launch only. In order for the FAA to issue future launch licenses, SpaceX themselves conducted the mishap investigation and submitted it to the FAA for review, complete with an itemization of some 63 proposed corrective actions that SpaceX would guarantee to implement before another launch would be licensed. Although we could not find the SpaceX mishap report in the public domain, we do know that several infrastructure corrective actions proposed by SpaceX included "redesign of the launch pad to increase its robustness." So the obvious question then becomes: "What were the root causes of the failure of the concrete portion of the "Stage 0" launch pad infrastructure?"  It is public knowledge that a special proprietary refractory concrete ("Fondag") was used by SpaceX-- a concrete mixture featuring synthetic aggregates and calcium aluminate cement--that reportedly performed just fine during a static mockup test firing done at roughly half of the Raptor engine cluster's max power. We also know from Tweet traffic posted the day after the mishap that SpaceX proceeded with its test launch despite missing a key Stage 0 component--a steel, water-cooled blast diverter plate--as described by the founder of SpaceX below: We may not ever see a complete account; since we were not able to access the SpaceX/FAA mishap report, and Elon Musk has yet to return inquiries from yours truly requesting a copy.  We have also been unable to find the identity of the concrete contractor--and the ready mix supplier--who worked on the Stage 0 infrastructure. At the time of this writing, SpaceX has obviously satisfied the FAA's requirement to prove the proposed corrective action punch list was implemented, since two subsequent Starship test launches have been made from the Boca Chica facility--the most recent on 14 March 2024--without any reported damage to the reinforced refractory concrete portion of the "Stage 0" structural frame.  There are several contemporary video accounts describing launch pad refractory concrete that can be found via simple internet search. Perhaps the best of the lot was produced after the November launch. Titled "What Exactly Happened to Starship, Did Stage Zero Actually Survive the Launch?", this interesting account and analysis can be accessed with this link. Another sensational video that showcases earlier SpaceX experiences with obliterated (and glowing) launch pad refractory concrete--along with an excellent treatise on refractory concrete in general--can be found in the Practical Engineering Concrete Series video called "Why SpaceX Cares About Concrete" at this link. After you have watched these videos, consider the account of a recent Starship launch (3 March 2024) as described below. ______________________________________________________________________________ Sidebar: To put the nuances of heat effects on concrete and embedded reinforcing steel into perspective, we consulted ASTM publication STP 169-D chapter 25: "Resistance to Fire and High Temperatures", where we learned the following by contributing author Stephen S. Szoke: When heated, non-refractory, normal weight concrete (NWC) dehydrates between 400 °F and 800 °F. It is in this zone when the "development of distress and a change for the worse" can begin. "The length of time before the steel reaches a critical temperature is when the moment capacity is reduced to the applied moment. In a fire this depends on the amount of cover to the steel and on the insulation properties of the concrete. The influence of cover is striking. For the same normal weight concrete exposed in a standard fire test for 1 hour, steel with only 1-inch cover would reach over 800 °F whereas, with 2-inch cover, the steel temperature would be about 400 °F.  With 3-inch cover, the steel would probably be hardly warm to the touch." Concrete-encased reinforcing steel bars will recover much of their lost strength when the bars cool and don't usually need to be replaced unless the bars are twisted or otherwise mechanically distorted. Jet engine exhaust can reach temperatures up to 1250 °F, 3500 °F at full afterburner; with a blast velocity of 3500 feet per second (fps). Although knowledge in the public domain is limited, rocket and missile engine exhaust temperatures may skyrocket to 5000 °F, with exhaust blast velocities up to 8000 fps. See below for more about ASTM STP 169-D... the so-called ASTM "Blue Bible". ______________________________________________________________________________ Full Disclosure, front story: On 16 July 1969, this writer's eyes and ears were glued to an old RCA black-and-white, rabbit-eared antenna TV set. The occasion? Countdown sequence and liftoff of the Apollo 11 "moon shot". Some might say that the visual portion of the live feed from the launch site was the money shot. But for this nerdy 13-year-old, the sounds of the launch sequence and the following booster staging callouts by the voice of Mission Control were the game changers. In fact, one wonders if those witnesses who experienced the event only via radio may have gotten the better part of that deal. Now...fast-forward to 3 March 2024, when the reusable SpaceX Falcon 9 "Crew Dragon" (as opposed to "Cargo Dragon") launched 3 NASA Crew-8 astronauts and one hitchhiking cosmonaut into low earth orbit (LEO) on the way to rendezvous with the International Space Station (ISS). No question--this was a magnificent night launch. Thanks to 55 years of technological advances, the sights-- and sounds--of the event could now be experienced using a hand-held device tuned to the social media platform called "X".  Once again, the voice of Mission Control and the entire audio feed from the launch site was sensational. (N.B. The launch audio-visual broadcast was committed to digital celluloid...you can hear the sounds plain as day with your own ears via the link to the official NASA broadcast given below.  The NASA broadcast video length is a bit less than 5 hours. The segments described below kick in at elapsed video time stamp at about the 4:09:00 mark at the bottom of the frame.  Also pay attention to the digital clock at the upper left-hand corner of the frame, or roughly T-minus 00:02:19). At T-minus 00:01:45, the voice of Mission Control repeats the announcement that the loading of liquid oxygen (aka "LOX load") into booster stage 2 is complete. At T-minus 00:01:29, gantry microphones are turned up, and we can hear the sound of gas venting from the Falcon 9 stack. At T-minus 00:01:15, this announcement comes from the voice of Mission Control: "Something else you might see here in a few moments is water being poured onto the pad...because rockets are super-loud, the sound can impart loads back on the rocket itself. So that water helps absorb and prevent the sound from hitting the structure and reverberating back on to the rocket". ___________________________________________________________________ Question: We are under subcontract to pump, place and finish (P-P-F) 12 floors of normal weight concrete (NWC) slab on metal deck (SOMD).  Each floor is being placed in two pours measuring 21,000 square feet (SF) each. We have been averaging 726 cubic yards (CY) per floor, placed with a 36-meter pump and a crew of 11 masons and 6 laborers. This mid-rise project was bid based on the P-P-F scope happening say late spring into mid-summer.  Due to a change in Ownership, the schedule was delayed, causing the project schedule to push the start of our deckfill scope into late fall. As part of the schedule recovery plan, the Owner cut us a change order to cover Saturday placement costs (e.g. overtime for all labor and mobilization cost for the concrete batch plant to open on a weekend). After 5 floors of same-kind work, our P-P-F crew settled into a nice, smooth rhythm. We outsmarted what little learning curve there was and went into cruise control from there.  We were in the middle of pour 2 on the 6th floor, about 150 CY in when KA-BOOM!!!! Our foreman called me and reported an unusually loud noise for a construction jobsite had just shaken everyone up.  Evidently, the general contractor (GC) had come down with a serious case of the vapors when he heard about it and told us to start thinking about setting an emergency construction joint (aka bulkhead) until they could figure out what happened. We had to call in carpenters and send a few of our labor crew along with the GC's lone guy on site--plus the inspector--to search every floor for apparent signs of damage. We also had to call the batch plant and tell them to put a hold on the delivery. Our foreman checked the top surface of the slab concrete placed earlier that day, and did not see anything unusual. Just when our carpenters arrived on site, we got a call from the GC telling us this was all a false alarm. The structural engineer advised that the loud noise was simply the steel building "settling" at some of the bolted connections, and it was OK to complete the day's concrete placement. The steel structure is founded on pile caps and grade beams. The piles extend down to bedrock. What kind of settlement could we possibly be talking about here? Answer: From your description, it appears the phenomenon your P-P-F crew experienced that quiet Saturday morning was what the steel trade refers to as "banging bolts". To oversimplify enormously, it is pretty much what the structural engineer said: the structural steel frame of the building is settling down (as opposed to settling in elevation). When this happens, the noise-especially to someone unfamiliar with the usual loud jobsite sounds- can be quite startling. Here at the ASCC Technical Division, we found a report in our vast archives of a 2015 case near Boston where the "bolt banging syndrome" at an elementary school caused the structure to be evacuated and shut down for a day. There appears to be competing theories that explain the root cause of the noise. But most agree such raucousness is caused when the faying surfaces in a slip-critical bolted connection overcome friction and actually slip, converting a slip-critical bolted connection into a bearing connection when the weight of the tributary area forces the connection to slip--and slams the steel at the connection down onto the bolt. In other words, at some point the applied loads overwhelm the friction between the steel faying surfaces and "kaboom!" The easiest way we found to get a grip on this is to view the first 3 minutes of a video presentation by Anthony Battistini, where the concepts of "slip-critical" and "bearing" bolted connections are clearly explained and demonstrated: As concrete contractors, we routinely set embeds fitted with shear tabs in concrete walls and column sides to carry future follow-on bolted structural steel members. It may be helpful for us to gain an understanding of the steel trade's work...and the occasional sounds a new steel frame can make when you least expect them. (N.B.: As ASCC Hotline callers know, if anyone wants to know about concrete building movement, all they need to do is visit a post-tensioned concrete structure during-- and just after--its construction.) ___________________________________________________________________ Question: About 14 months ago, we installed a raised concrete "aeration floor"--16 inches above the slab on ground--inside a 48-ft. diameter sheet metal grain storage bin. The 1810 SF concrete slab was placed over a proprietary corrugated metal deck and steel vertical support system. The 40-ft. tall grain bin enclosure is corrugated steel as well.  Nominal concrete compressive strength was specified at 4000 psi.  Out here in our market, such grain bin work is commonly accomplished with off-the-shelf, brand "X" ready mix concrete featuring a simple bull float final surface finish. After about a year in service, there was a grain fire inside of the structure. Once the debris had been removed, the Owner asked us to perform a quick condition survey of the slab.  The top slab surface was charred, to be sure, but otherwise (in our opinion) the slab looked just fine.  An informal "Swiss hammer" rebound test was performed, and all indications were that the concrete appeared to have 4000 psi compressive strength--or better. Nevertheless, the structural engineer is saying he recommends the slab be removed and replaced. The Owner and his insurance carrier have not yet decided on a course of action. Does the ASCC Technical Division/Hotline have available any literature that discusses fire damage to a concrete slab? We have no skin in this game; but the Owner is a good, long-time customer, and in the name of excellent ASCC contractor customer service we want to provide backup that can support our belief that the existing slab is fit for purpose. Answer:  We are sending to you (under separate cover) some industry documents that discuss how to approach and assess fire damage to concrete.  It appears the Owner and the insurance company are on the fence regarding the "remove and replace" option. Because you were approached strictly as a "consultant" to weigh in as viewed through the lens of the concrete contractor of record, perhaps you might float an option that might just help convince all stakeholders to reconsider...and declare the existing slab fit-for-purpose. Propose the Owner have 4 cores taken in the "worst" area of each quadrant of the slab. This would allow both visual examination and compressive strength testing to confirm the concrete strength in place is 4000 psi or better. Since you are likely to be the contractor of choice if the "remove and replace" option is used, you can easily estimate the costs involved and compare your number to the quote for testing the Owner solicits from his test lab.  Might well be an investment worth making for all stakeholders.  One thing's for sure: if the remove and replace, "scorched earth" option is implemented, it should be a simple matter to sift through the wreckage and see with you own eyes the visual condition of the concrete.  We can tell from your description of the ready mix that the possibility of fire damage inside a metal grain bin may not have been on the engineer's mind during design.  In other words, the mix design used in the original construction did not include any "refractory" ingredients. Either way, it's win-win for you. ________________________________________________________________ Question: We have a poured slab with a crooked spot in a sawcut joint as shown in the attached photograph. We are unable to find any documentation regarding the tolerances for sawcuts. Are you aware of anything regarding this issue? Answer: Let not your heart be troubled. The edge of the yellow level is set at the theoretical design plan center of the sawcut. It appears that the sawcut has wandered roughly a quarter inch to the right of perfection. If the concern is horizontal plan location of the as-built sawcut, you are home free. According to ACI 117-10 Specification for Tolerances for Concrete Construction and Materials section 4.2.1, the horizontal sawcut deviation is specified as plus/minus 3/4-inch. The ACI 117-10 commentary section R4.2.1 confirms this tolerance is "driven by aesthetic concerns", e.g. not a structural concern per se. Should the depth of the sawcut become an issue, ACI 117-10 section 4.9.1 specifies the depth of the sawcut joint can deviate from nominal design depth with a tolerance of plus/minus 1/4 inch. ___________________________________________________________________ Insider's note: Here's another extremely high-value concrete industry reference book that ASCC members should consider adding to their library: "Significance of Tests and Properties of Concrete & Concrete-Making Materials".  Published by the American Society for Testing and Materials International (ASTM), this 664-page manual is now available in both hard copy and searchable pdf (stock number STP 169-D). Here in the ASCC Technical Division, we refer to it as the "Blue Bible". If you visit this link, you can read the particulars, along with a free pdf file called "STP Individual Article Download" that provides the table of contents; titles of all 57 chapters, and authors of each chapter, including chapters written by concrete experts Ken Hover and Colin Lobo. Highly recommended. __________________________________________________________________ Question: We know flat slabs aren't perfectly level and some ponding should/could be expected. Are you aware of any code, standard or literature that discusses ponding water on a slab and what is an acceptable timeframe for evaporation of the water? Answer: There is plenty of literature published by the ASCC Technical Division regarding birdbaths on concrete slabs. ASCC Position Statement #7: Birdbaths on Concrete Slabs tells us that--as you say--expectations of birdbath-free work are unrealistic. We are sending to you under separate cover a copy of a Concrete International article titled "Birdbaths: Expectations vs Reality" written by Bruce Suprenant, which explores the birdbath phenomenon in detail. Perhaps the best technical explanation of the birdbath phenomenon--and why a birdbath-free slab surface is impossible to build--appears in the ASCC publication called "Tolerances for Cast-in-Place Buildings", a tour-de-force tolerance book authored by former ASCC Hotline Operators Bruce Suprenant and Ward Malisch. Here's one of several birdbath examples from that ASCC tolerance book: Unfortunately, we cannot find any mention of allowable expected water evaporation time in ASCC, ACI, or other concrete trade publications. But sometimes we can venture out of our concrete world and see what's in the other guy's playbook. In this case, we find what we are looking for-- published by our colleagues in the residential home building business. According to the National Association of Homebuilders (NAHB) publication titled "Residential Construction Performance Guidelines: Consumer Reference, Fifth Edition", the issue of birdbath water evaporation time appears in several sections related to residential concrete (and some asphalt) work as follows: For Driveways and Sidewalks, the NAHB Performance Guideline in section 12-4-2 for asphalt pavement states "Standing water greater than 3/8 inch in depth should not remain on the surface 24 hours after a rain". For Driveways and Sidewalks, the NAHB Performance Guideline in section 12-4-7 states "Standing water that is 3/8 inch deep on a sidewalk 24 hours after the end of a rain is considered excessive". For Concrete Stoops and Steps, the NAHB Performance Guideline in section 12-2-2 states "Minor amounts of water can be expected to remain on stoops and steps for up to 24 hours after rain". (N.B.: If you really want to know the truth about it all, the wording in sections 12-4-2 and 12-4-7 seem borderline questionable. But hey--at present--that's the best we can find in print for rainwater. On the other hand, bleed water evaporation time is an unrelated--but currently popular--topic of interest when the discussion turns to initial curing of concrete slabs). ___________________________________________________________________ Question: We are building a concrete parking structure that features two floors below street level. Once the sheeting and shoring was completed, the first order of business for us was to place a 3-inch-thick mud slab over some 40,000 square feet (SF) of real estate. We placed the mud slab in one mobilization on a Friday in 30° F weather.  The next concrete placement on the schedule was for a 4-ft. thick foundation mat slab. We brought a 3-man layout crew in on Saturday to establish control lines on the newly placed mud slab and then lay out the concrete outlines for every wall and column.  We use blue chalk line and bright orange spray paint to preserve the lines and to make them easy to see when standing on the top mat reinforcing steel, or when dropping a plumb bob down 4 feet to transfer up the outlines for wall and column rebar templates to be attached to the top layer of steel. (As any veteran ASCC concrete contractor can tell you, spending a little overtime for the layout crew on a Saturday helps reduce the grief factor first thing Monday morning when the rebar guys start flying 60-ft. long bundles of #11 bars into the hole is money well-spent.) The ambient temperature on Saturday morning was still below 30° F, so we decided to fly an empty 50-gallon trash drum down into the hole to use as a fire barrel. We looked down in the hole, and could see some random people down there who were gathered around a good-sized fire on the mud slab. The problem we had was how to evict these uninvited jobsite visitors. One of our crew hollered to them and asked them to leave, but they ignored the request. We were just about ready to call the police when our superintendent showed up. He told us not to do anything--these folks would soon be gone. The three of us went out and hollered some more, and the visitors took the hint and left the site...without putting out the campfire. A few minutes later, we watched and listened as the mud slab concrete under the campfire exploded, sending debris everywhere.  We have told this story to several people in our main office, but no one believes it was the concrete that exploded.  On the jobsite, anyone could see plain as day where the mud slab needed to be replaced. Does the ASCC Technical Division have any information about exploding concrete? Answer:  Under the right conditions, concrete can indeed explode. The phenomenon is defined as "explosive spalling" as reported in ACI 547R-79(97) Refractory Concrete: Abstract State-of-the-Art Report as follows: "EXPLOSIVE SPALLING- A sudden spalling which occurs as the result of a build-up of steam pressure caused by too rapid heating on first firing." Further explanation is offered in section 6.4 Drying as follows: "The large amount of free water in the refractory concrete necessitates a drying period before exposure to elevated temperatures. Otherwise, the formation of steam may lead to explosive spalling during firing." There are a raft of videos and news reports that feature cases where highway pavements in Missouri and Louisiana, for example, exploded due to elevated daytime pressure that built up inside the roadway slabs. Those can be found by simple internet search. If you want a scientific laboratory research example, there is a short, roughly 1-minute video titled "Concrete Can't Burn, But it Can Blow Up", produced by the LiveScience channel.  ___________________________________________________________________ (N.B.: Any and all references--however oblique--to work product by Gibbons, Hill, Beard and Robert Weston Smith in the above are purely intentional.  If you know...you know.  References available upon request for most anything you see reported above.) ___________________________________________________________________ rzuellig Mon, 01 Apr 2024 14:39:00 GMT f1397696-738c-4295-afcd-943feb885714:437 https://ascconline.org/Home/News/articleType/ArticleView/articleId/436/ASCC-Technical-Team-Staying-Busy#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=436 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=436&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/436/ASCC-Technical-Team-Staying-Busy Mike Hernandez, Technical Director, The Voice Newsletter March 2024 The current and future challenges of concrete construction are what the ASCC Technical staff focuses on each day. Those challenges can come in many forms. Jim Klinger has a vast library of documents and decades of experience in structural concrete and receives Hotline calls. Clark Branum, the Decorative and Polished Concrete Specialist, knows the proper steps for numerous decorative and polishing solutions. Clark is working through several best practice documents and a polishing position statement. In addition to engaging urgent member issues, I am looking forward to what ACI, ASTM, emerging technologies, and now what sustainability expectations are going to be placed on the members and to see if we can lighten the burden. The goal is to provide the contractor’s perspective while documents are still in draft review. Once ACI publishes a document, it will be years before it changes. American Concrete Institute (ACI): The ACI Convention in New Orleans will take place March 23rd-27th. A hot topic continues to be Type IL/portland limestone cement (PLC). There will be several two-hour sessions on experiences with PLC as well as two sessions on “Who is Responsible When Sustainable Concrete Does Not Meet Performance Expectations?” The ACI staff stated they plan to record these sessions for future viewing on their website. ASCC is working with the ACI 302 committee to perform a collection of industrial floor slab mixes using Type I/II, or II/V where higher sulfate resistance is needed, and now Type IL mixes. Once a comprehensive group is collected, we will run comparison tests to give guidance on what to focus on when transitioning to IL on hard-troweled slabs. We are still evaluating the technical feasibility of having an artificial intelligence (AI) platform run the initial analysis. The degree of support we receive from allied organizations, ACI, NRMCA, and PCA will affect the scale and speed of this effort, probably even its success or failure. This is a complex issue where one or two solutions are not an option. With 25 ASCC voting members plus 39 consulting and associate members, we should have enough projects to draw from to have the collection effort done quickly, for an ACI group. Also intend to request support from ASCC’s Finishing, Constructability, and Technical Committees. Member Engagement Visits: I am going to be in Atlanta, Georgia visiting members for a few days 3/19-3/20 on the heels of an NRMCA’s technical committee nearby. Would like to make myself available for 2-3 hours to discuss member companies’ specific challenges in person when I am already traveling to a nearby city. The further in advance the planning, the more likely I can visit your team. My travel in 2024 currently includes: rzuellig Mon, 01 Apr 2024 14:36:00 GMT f1397696-738c-4295-afcd-943feb885714:436 https://ascconline.org/Home/News/articleType/ArticleView/articleId/416/Guidance-for-Concrete-Contractors26-in-a-Series#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=416 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=416&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/416/Guidance-for-Concrete-Contractors26-in-a-Series Jim Klinger, Concrete Construction Specialist The Voice Newsletter February 2024 The Use of Laser Scanners Full Disclosure:  Imagine, if you will, the following scenario. You are an experienced project manager, patiently waiting to collect your retention for the reinforced structural concrete portion of a large, wood-framed condominium project. The stick framing begins at grade level--there are no basement or subterranean parking levels. The reinforced concrete slabs on grade are your standard brand "X" variety:  6 inches thick, 4000 psi at 28 days.  Mid-depth reinforcement is #4 bars at 16 inches on center, each way (OCEW), supported on precast dobies on 15-mil vapor barrier over a well-prepared subgrade.  Each slab on grade features a 9000 square foot (SF) footprint, 45 feet wide and 200 feet long, with sawcut control joints spaced at 15-foot centers in both directions. There are no reinforced concrete columns or masonry walls, but sill plate anchor bolts and seismic hold-downs for the vertical wood framing abound. Your subcontract scope included 15 each of the 9000 SF slabs on grade. Looking back over the job, you did everything by the book. The schedule and concrete placement logistics for each of the 167 neat cubic yard (CY) pours were carefully choreographed, thanks to close collaboration with the general contractor (GC), the ready-mix supplier, and the City. During the preconstruction meeting, all parties discussed the specified floor flatness requirements-- and agreed on the means and methods the Owner's inspection agency would employ to determine contract compliance. Your finishing crews had no problem meeting the specified overall floor flatness and levelness callouts of FF 35/FL 25. Each and every test report indicated all flatness and levelness testing was completed and reported within the allowable 72-hour window, and your work product passed with flying colors. No overtime was needed for your finishing or labor crews, and your overall job cost is looking good. There were a minimal amount of punch list items, all completed and signed off 6 months ago. Due to pandemic-related supply chain problems, the wood framing subcontractor is just now mobilizing on the jobsite. Almost all of the follow-on trades have been delayed as well. But your work is long since complete-- all you are doing now is waiting for your retention payment. And then the unthinkable happens.  You get that email...or that phone call...from the GC. The follow-on flooring subcontractor has commissioned an as-built survey of your slab surfaces, conducted with a laser scanner last week. The GC transmits a multi-colored survey plan--a so-called "heat map"--to you, along with notice that your retention payment is now on hold. In essence, the GC tells you "Here's the heat map that shows your work is in the wrong place, and now you owe me cash".  Or "now you owe me grinding."  Or "now you owe me leveling compound".  The GC typically ends such notices with "The project has already been delayed, you need to get your repair crew out there now to commence fixing the floors.  And don't forget to submit your recovery schedule". Sometime during 2017, the ASCC Hotline began fielding phone calls from contractor members who had been to the movie described above.  In fact, they had front-row seats. ASCC members were being presented with heat map plans and told their work was not in compliance with the construction documents and backcharges were being prepared. The ASCC Technical Division disagreed. Since there was no published guidance in the industry literature that described the use of laser scanners to determine top of concrete slab contract F-number compliance, ASCC designed a study to test and report the tolerance-measuring performance of 8 laser scanners to Joint ACI-ASCC Committee 117 Tolerances. The ASCC study and its results were presented in the ACI Concrete International January 2019 and February 2020 issues.  Were the GC's justified in backcharging ASCC contractors based on laser scanner heat maps? In a nutshell, the results of the 2018 ASCC study showed that we were unable to recommend the use of laser scanners to determine contract F-number tolerance compliance. In other words, we believed that laser scanning technology--while quite useful in other concrete construction applications-- was not ready for prime time for contract F-number tolerance compliance purposes. By-products of the ASCC study included two very successful Laser Scanning Workshops held at the World of Concrete, formation of ACI 117 Subcommittee 117-L Laser Scanning and drafting of a new ACI-ASCC tolerance document (still in progress) with the working title "Guide to the Use of Laser Scanning for Concrete Tolerances". Fast-forward now to 2024. Laser scanner technology continues to evolve, and the use of these instruments is becoming commonplace among ASCC contractors for various applications. We still believe reliable laser scanner use for F-numbers is out on the horizon. But has the technology progressed to the point where the laser scanners can be used to reliably evaluate other ACI 117 tolerances e.g. tolerances for plumb, elevation and location? Part of the answer lies in the September 2023 ACI Concrete International article titled "Laser Scanning Basics for Concrete Tolerance Verification", co-authored by ASCC member Conco's Leo Zhang (Chair of ACI Committee 117-L) and the U.S. Institute of Building Documentation's (USIBD) John Russo. Currently, concrete contractors are using laser scan technology in planning and preconstruction phases to evaluate staging, safety and truck routing. Laser scanners are effective in quickly assembling volume calculations for mat pours and for determining extra perimeter wall concrete needed when below-ground shoring is misplaced. The laser scanners are also being used in certain Quality Assurance/Quality Control (QA/QC) applications as well as Building Information Modeling (BIM) deliverables. But according to Zhang and Russo, there is still testing that needs to be done. To that end, Zhang has recently issued a two-page "Call for Participants: A Laser Scanning Interlaboratory Study on Selected ACI 117 Tolerance Compliance Verification". The proposed testing would be similar to the original 2018 ASCC study conducted in Walnut Creek, California. Testing would take place on a San Francisco Bay Area construction jobsite on a Saturday and Sunday in July 2024, actual weekend dates TBD.  Both vertical and horizontal concrete elements would be tested. Ten participants are envisioned to take part representing different U.S geographic regions.  In addition to data collection, results of the July 2024 study will be submitted for a future ACI Concrete International presenting a compilation of best practices learned from the study. For more information, contact Leo Zhang, 925-348-5309, lzhang@conconow.com. ASCC 3-D Laser Scanning Study, Part 1, Concrete International January 2019 and Part 2, Concrete International February 2020 Laser Scanning Basics for Concrete Tolerance Verification, Concrete International September 2023 ____________________________________________________________________________________________ The Lombardi Rule Question:  I attended a safety meeting held last spring at one of our jobsite trailers. Before our meeting convened, I caught part of a speakerphone conversation among our field superintendent, our carpenter foreman, and the ASCC Hotline. The discussion I overheard was related to the quality of architectural concrete wall surface finishes. It sounded like the architect showed up to our jobsite with a magnifying glass to review the latest lift of shear walls; poured a week prior and stripped 2 days after concrete placement. I kept hearing the term "Lombardi Rule" used by the Hotline operator, but unfortunately was unable to hear the balance of the conversation. Evidently, the dispute with the architect was settled and I have been too distracted follow up until now.  What exactly is the "Lombardi Rule", and how can such a rule be used by ASCC members? Answer: The so-called "Lombardi Rule" is an informal shorthand term coined by a Hotline operator here in the ASCC Technical Division. The term is used when referring to the "final acceptance of architectural concrete" determination procedure stated in ACI 301-20: Specifications for Concrete Construction. According to ACI 301-20, section 6.3.12 specifies the following procedure: "Upon completion of architectural concrete, including surface repairs and patching of tie holes, final acceptance is based on matching the architectural cast-in place concrete with accepted field mockup when viewed at 20 ft in daylight." The "Lombardi" part is a sentimental old-school tribute to Vince Lombardi (1913-1970), legendary National Football League (NFL) coach and author of "Run to Daylight". The Lombardi Rule should be invoked by a concrete contractor when the reviewer of an architectural concrete surface stands a few feet away from the work and then pronounces the work unacceptable based on "defects" (e.g. bugholes, etc.) as seen--and then subjectively judged--from only a few feet away. A more detailed explanation of the Lombardi Rule can be found in ACI 347.3R-13 Guide to Formed Concrete Surfaces, which explains that "when evaluating exposed concrete surfaces, the overall impression viewed from an appropriate viewing distance is the main method of evaluation". But what constitutes an appropriate viewing distance? ACI 347.3R-13 section 7.2 provides the answer as follows: It should be noted here that the application of the Lombardi Rule should be discussed at every preconstruction conference where architectural concrete is part of the scope of work. In some cases, construction documents may call for a viewing distance less than 20 feet. ASCC members who specialize in tilt-up work, for example, should be mindful that ACI 301 section 12.3.9(a)(d) specifies a viewing distance of only 10 feet for evaluation of tilt-up panels that require a Smooth Panel Finish 3 (SPF-3). rzuellig Mon, 26 Feb 2024 19:04:00 GMT f1397696-738c-4295-afcd-943feb885714:416 https://ascconline.org/Home/News/articleType/ArticleView/articleId/415/ASCC-Collaboration-Increases-to-Maintain-Concretes-Role#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=415 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=415&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/415/ASCC-Collaboration-Increases-to-Maintain-Concretes-Role Mike Hernandez, Technical Director The Voice Newsletter February 2024 As we begin 2024, ASCC collaboration with other trade associations continues to expand. The challenges with concrete expectations and particularly with low carbon concrete can’t be solved by the concrete contractor alone. Concrete has traditionally competed to be the paving and building material of choice with asphalt, structural steel and masonry.  Now the wood industry has compared concrete unfavorably with heavy timber structures. In response, concrete construction needs increased collaboration within the allied groups of ready mixed producers, cement manufacturers, specifiers/design professionals, testing labs and owners. That cooperation can be in the form of working together on joint programs, within ACI Committees, at ASTM, on government grant proposals or general best practice.  ASCC has maintained a relationship with the National Ready Mixed Concrete Association, NRMCA, since the early 2000’s. This comes in the form of co-authoring documents, such as the P2P and pre-construction checklists, review of the AIA specifications or articles for Concrete International. Brian Killingworth is a Special Director on the ASCC Board. Brian supports the NRMCA/ASCC Joint Paving Committee which provides the opportunity for contractors to take the NRMCA paving bootcamp and engineering assistance on conversion of projects from asphalt to concrete pavement. Former ASCC Technical Director, Ward Malisch, was part of the NRMCA Research, Engineering and Standards, (RES) Committee, and I have joined on behalf of ASCC. Several other ASCC contractors and I are engaged to provide the contractors’ perspective. An RES member provided the idea for placing inexpensive sensors in jobsite early age curing boxes to monitor the temperature. Initial curing at outside the ASTM 60F-80F range will yield inaccurate cylinder test results. I am working with several ASCC contractors and ready mixed producers in the Denver area and nationally to gather data on early age curing temperatures. NRMCA supported the recent ASCC proposal for EPA research funding. Even if unsuccessful in this specific request, we have set the groundwork for future research projects. Several state ready mixed concrete associations are also ASCC Members The Portland Cement Association, PCA, and ASCC are working together more. Since the ready-mixed producer is the cement manufacturer’s customer, this can be an indirect relationship. Through discussions with quality and conscientious contractors, knowing your local cement options and properties has become more important than it once was.  PCA and ASCC joint sponsored a World of Concrete session on Portland Limestone Cement/PLC Best Practices. In the session ASCC Contractors, NRMCA concrete producers and a PCA cement manufacturers recounted how they worked together on specific projects making trial batches and field mockups to confirm finishability and hardened concrete goals. PCA has been welcomed to participate in our monthly Voice newsletter and Michelle Wilson recently joined the ASCC Board of Directors as a Special Director. Among the ASCC Members are a handful of companies that are also PCA Members. ASCC’s long-term relationship with the American Concrete Institute, ACI International, is ongoing. ASCC members serve on over 40 ACI Committees. There are two joint ACI-ASCC committees, 117 tolerances and 310 decorative, with 301-0J Polishing subcommittee. ACI, ACI NEU and ACI Pro have joint memorandums of understanding, MOUs, for collaboration with ASCC. Mike Tholen, ACI staff and ASCC Special Director, Phil Diekemper with PRO and Dean Frank from NEU have open lines of communication with ASCC staff. The ASCC Sustainability Committee has members of other trade associations, including the Concrete Reinforcing Steel Institute, CRSI, the National Council of Structural Engineering Associations, NCSEA, the previously mentioned associations as well as general members. A member from DPR also serves on an AGC sustainability committee. ASCC seeks to understand AGC’s plans and expectations as well.    ASCC recently joined the National Institute of Standards and Technology, NIST, Low Carbon Cements and Concretes Consortium. Among other things it seeks to set specification standards for low carbon concrete, which is in the long-term interest of ASCC members. There are even more concrete association formal affiliations that have not been finalized which will support our members. We are all working together to maintain concrete’s role as the paving and building material of choice for strength, durability and sustainability.   rzuellig Mon, 26 Feb 2024 19:02:00 GMT f1397696-738c-4295-afcd-943feb885714:415 https://ascconline.org/Home/News/articleType/ArticleView/articleId/405/Guidance-for-Concrete-Contractors-25#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=405 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=405&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/405/Guidance-for-Concrete-Contractors-25 Jim Klinger, Concrete Construction Specialist The Voice Newsletter January 2024 Full Disclosure: One of the most valuable concrete industry documents that will ever cross the desk of an ASCC member is ASTM C94: Standard Specification for Ready-Mixed Concrete. Its companion document (prepared jointly in 2014 by the American Society for Testing and Materials (ASTM International) and the National Ready Mixed Concrete Association (NRMCA), see cover shot, below) is titled The User's Guide to ASTM Specification C94/C94M on Ready-Mixed Concrete: 2nd Edition. Worked in tandem, these two documents present and explain the technical background, legal particulars and associated stakeholder responsibilities that surround the materials, manufacture, mixing, delivery, testing, and purchase of ready-mixed concrete. What follows below relies heavily on both the Standard Specification (hereinafter referred to as "ASTM C94") and the User's Guide (aka "The Guide"). ___________________________________________________________________________ If you are a concrete contractor doing business here in the U.S., you have little choice but to become fluent in the entire ASTM C94 document--or at least be familiar enough to be able to find what you need, when you need it. As a stand-alone industry standard quality specification, ASTM C94 is neither a quick nor easy read. But thanks to co-authors Daniel and Lobo, the content of ASTM C94 is carefully dissected and explored--section by section--much to the benefit of all project stakeholders and readers of The Guide. According to The Guide, ASTM C94 is "written to the purchaser or general contractor to allow the owner to identify who is ultimately responsible for the entire concreting operation. ASTM C94 is also written in an attempt to separate the responsibilities of the concrete manufacturing process and product delivery from the overall responsibilities of the general contractor or a concrete contractor. This separation is needed for clarity in a purchase order for concrete or a delivered materials contract whether written or oral." According to ASTM C94, the term "ready-mixed concrete" is defined as "concrete manufactured and delivered to a purchaser in a fresh state." Accordingly, the term "purchaser" typically refers to the concrete subcontractor who orders concrete on behalf of the owner. In other words--just so we're clear-- the concrete contractor is usually the purchaser. At the date of this writing, the latest available version of ASTM C94 is designated ASTM C94/C94M-23. On the other hand, the 2014 copyright date of the User's Guide 2nd Edition indicates the document is based on ASTM C94/C94M-13. In other words, there is roughly a 10-year spread between these companion documents (more on that below). If purchased today, ASTM C94/C94M-23 (16 pages) is listed at $69.00, while The Guide (MNL49-2ND-EB, 160 pages) can be purchased from ASTM International in either soft-cover hard copy or in searchable pdf format for $89.00. The Guide is also advertised by NRMCA for purchase at a discounted price of $75.00 for NRMCA members. There are currently no plans for a 3rd Edition of The Guide. ______________________________________________________________________________ Question: We are preparing the agenda for an upcoming preconstruction conference. Our contract scope features the reinforced concrete portion of two identical structural steel office buildings and an adjacent post-tensioned (PT) concrete parking structure. At bid time, the total concrete material purchase quantity was estimated at 43,365 cubic yards (CY), counting shotcrete. Our concrete supplier is still compiling the backup data required by ACI 301 and ACI 318 to support the mix design submittals and will request design team approval to be able to adjust the slump (and possibly entrained air content) in cases where preliminary jobsite testing reveals slump or air test measurements higher than those specified in the construction documents. Any adjustments would be accomplished at the truck by using site-added proprietary ASTM C494 Type "S" (specific performance) slump reducing or air-detraining admixtures. We are hoping to get the proposed admixture product data cut sheets, manufacturer's printed installation instructions (MPII), and safety data sheets included in our first round of mix design submittals, along with any available trial batch performance data. The idea is to have this initial submittal in the design team's hands at least a week before the preconstruction conference. We will also ask the GC to float a preview copy of our mix design submittal to the owner's inspection agency for their use. Our project engineer has reviewed the NRMCA/ASCC Checklist for the Concrete Pre-Construction Conference and found jobsite slump adjustments addressed in Section C-14; but there are only three materials listed as potential permitted admixtures: water, mid-range water reducer (MRWR) and high-range water reducer (HRWR). The water and water-reducers are used to increase the slump, not reduce it. This upcoming project will be the largest we have ever done, both in terms of total concrete cubic yards (CY) and number of different concrete mixes needed--including lightweight concrete (LWC) and shotcrete. We have no experience with such site-added admixtures and want to make sure we understand the jobsite concrete adjustment protocols for slump and air reduction before we walk into the meeting. Please advise. Answer: The protocols are given in ASTM C94, section 17: Sampling and Testing Fresh Concrete. In your case, the applicable section is 17.6.1, since preliminary check testing at the front end of the load is assumed by your supplier to indicate results greater than specified as follows: Thanks to the authors of The Guide, the supporting rationale is explained as follows: "A preliminary sample is permitted to be taken after the discharge of at least 1/4 CY. The purpose of the preliminary sample is to permit adjustments to the load if required. This preliminary sample is to be used only for checks of slump or slump flow and air content to determine whether these properties are within the specification limits. The preliminary sample does not need to be very large but should not be the first 1/4 CY discharged. One-fourth cubic yard is not a trivial amount; it is approximately 1000 lb. of material, which must be discharged prior to taking the preliminary sample. Nothing prohibits this discharge into the project. One of the primary purposes of this preliminary sample is to avoid making adjustments to the load for air content and slump after a significant portion of the load has been discharged, which is what occurs when an acceptance sample in accordance with ASTM C172/C172M is obtained. When a sample from the middle of the load is obtained and the slump, slump flow, or air content does not comply with the specification requirements, the quantity of concrete in the truck will be unknown. Making adjustments at a later point will be purely guesswork. The preliminary sample should not be used as the acceptance sample for the molding of strength specimens. It is tempting to proceed with casting strength test specimens when slump or slump flow and air content requirements are met, but this is not acceptable. If the same truck is to be tested, acceptance samples should be obtained at a later point in the discharge and all tests should also be performed on that sample". So, what happens when preliminary check test results indicate slump or air greater than specified? Section 17.6.2, for example, mentions adjustments for results less than specified. Once again, the authors of The Guide offer the following instructive commentary: "No mitigation procedures are currently addressed within ASTM C94/C94M for slump or air contents greater than desired. Thus, no mention is made of the possible use of air-detraining admixtures or slump reducing agents. Such products are available, are often used, and may be desirable by both the producer and purchaser to save the load and keep the delivery of concrete moving. ASTM currently takes no position on the use of these products. The check test on the second preliminary sample is performed before any additional concrete is discharged. If the results of this second test are outside the acceptable limits for the project, the concrete shall be considered as failing the specifications and may be rejected for use on the project or otherwise handled in accordance with project requirements. The purchaser still has the ability to accept the concrete. The purchaser's representative on the job site with the appropriate authority needs to make the judgement as to whether the deviation from the specification requirement is of significance to the requirements of the project and whether the cost and delay associated with rejecting the concrete are justified." In addition to the consideration of air-detraining or slump reducing admixtures by your project design team, another key takeaway showcased by The Guide (and fair game to be placed on the table at your preconstruction conference) is that concrete cannot be rejected on the basis of a single test of slump or air content--it takes two tests to fail. The concrete can only be rejected if both the first test and the subsequent check test fail. Without two tests, the concrete may be improperly rejected, leading to disputes about who should pay for the rejected concrete. And, as noted in The Guide, the purchaser still has the ability to accept the risk and authorize placement of the concrete anyway, despite the results of two apparent failed tests. Question: Since there is a 10-plus year spread between publication dates of ASTM C94 and The Guide, does that not render The Guide obsolete? Answer: Not at all. Although the wheels of progress in the world of industry standards grind slow, it is true that ASTM C94 has been revised since the 2014 publication of The Guide. But the basic framework of ASTM C94 remains largely unchanged. Accordingly, the sheer amount of comprehensive research and backup reference material presented in The Guide help that publication maintain its value. rzuellig Wed, 17 Jan 2024 14:00:00 GMT f1397696-738c-4295-afcd-943feb885714:405 https://ascconline.org/Home/News/articleType/ArticleView/articleId/404/ASCC-at-World-of-Concrete#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=404 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=404&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/404/ASCC-at-World-of-Concrete Mike Hernandez, Technical Director The Voice Newsletter January 2024 Looking forward to our World of Concrete ASCC committee meetings, booths and events, 1/21/24 – 1/25/24. Committee meetings start Sunday afternoon 1/21 with MAC Board and Finishing Committee. All ASCC members are welcome to attend almost all committee meetings, with few exceptions. In case you missed it, PLC Alert! 2 was issued last month, and portland limestone cement concrete continues to be a hot topic in committee meetings. Other projects are also in progress. Don’t miss the Kick-Off Bash Monday evening. It is our best party at WOC. The Decorative Concrete Experience will be a booth sponsored by ASCC, the DCC, and the CPC. Members have been working hard for months to make it educational and fun, located in South Hall booth S13927. In addition, ASCC’s regular booth will be located at Central Hall booth #C4511 ASCC is cosponsoring three sessions at WOC and helped recruit the panelists. The Polishing Luncheon and Open Forum on Tuesday 11:30 am – 1:30 pm. Session ID: TUCPL From the WOC program: “Evaluating concrete floors before polishing is one of the most arduous estimating efforts for concrete polishers. Polishers must manage owner expectations concerning timelines, costs, and final appearance. The Concrete Polishing Council (CPC) of the American Society of Concrete Contractors (ASCC) recently published two contractor-focused documents (CPC Position Statements 6 & 7) that will provide support for contractors during meetings with project owners.” Polishing Panelists: Bob Harris, Structural Services Inc., Temple, GA Chris Wright, Durable Surfaces, Malvern, PA Ryan Klacking, Concrete Polishing Council Advisory Board, Dearborn, MI The Slabs Luncheon and Open Forum on Wednesday 11:30 am – 1:30 pm. Session ID: WESOG From the WPC program: “Innovations in Concrete Slab Construction– True Innovation doesn’t come easily in our business. But the four experts on this panel can tell you what’s new, and what works and what doesn’t. Each presenter will make a short presentation about one aspect of slab construction, then attendees will have the chance to ask questions about anything related to concrete floors.” Concrete Slabs Panelists: Scott Tarr, North S. Tarr Concrete Consulting, Dover, NH Bryan Birdwell, Structural Services Incorporated, Waxahachie, TX Jonathan Matson, Somero Matson Group, Archdale, NC Greg Fricks, The Fricks Company, Fort Worth, TX. Best Practice for PLC (Type IL) on Wednesday 2:00 pm – 4:00 pm. WOC Session ID: PLCWE From the WOC program: “This session will provide information for the user on best practices for sustainable concrete. Topics will include what steps should be taken in the preconstruction phase when using portland-limestone cement (Type IL) in construction projects. This session will include a panel discussion with cement suppliers, ready-mix producers, and concrete contractors moderated by ASCC & PCA staff.” Topics of the presentations and discussion include: Planning for sustainable concrete construction using Type IL cement Meeting both engineering requirements and constructability requirements Examples from multiple projects which implemented Type IL cement Can’t wait to see everyone! rzuellig Wed, 17 Jan 2024 13:58:00 GMT f1397696-738c-4295-afcd-943feb885714:404 https://ascconline.org/Home/News/articleType/ArticleView/articleId/390/Guidance-for-Concrete-Contractors-24#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=390 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=390&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/390/Guidance-for-Concrete-Contractors-24 Jim Klinger, Concrete Construction Specialist, The VOICE Newsletter December 2023 Full Disclosure: Perhaps one of the most unwelcome telephone calls a concrete construction project manager could ever get usually comes first thing the Monday morning following a Friday foundation concrete placement that required setting of large anchor rod assemblies for follow-on steel buildings. Such phone calls always start with the general contractor (GC) saying that the steel erector's licensed surveyor has just completed his routine as-built location check and discovered a number of anchor rods are in the wrong place. The steel erector reports that all the project's steel column base plates have already been fabricated, welded to their respective columns, and loaded onto trucks awaiting imminent jobsite delivery. Furthermore, steel erection is scheduled to start in a week, and it now appears that these trucks will have to be unloaded so the affected column base plates can be taken back into the shop to be reworked. In some cases, the anchor rods appear to be so far out of place that the structural engineer is going to have to drop what he is doing and review each condition and advise on potential fixes. ("The engineer isn't in yet, but hey- we have a call in to his office", says the GC). The phone call continues with the GC advising that all handling, refabrication and all other associated costs will appear as back charges via a deductive change order to your subcontract as soon as all rework is complete, including any delay impacts to the steel erector or other trades affected by your field errors. Of course, the Owner's inspection agency must also perform unplanned steel fabrication shop inspections of the base plate rework, so those costs and any structural engineering fees will be rolled into your back charge as well. The GC concludes the phone call with an engraved invitation to an emergency meeting with the Owner to be held this afternoon in the jobsite trailer at which your attendance is mandatory. "Be prepared to discuss the base plate rework, schedule impacts, impacts to other trades, and your proposed schedule recovery plans", says the GC. The ASCC Hotline call depicted below represents a classic case where a simple--yet inconspicuous--detail was overlooked. Even with the best intentions and due diligence during the preconstruction and construction phases, sly little booby traps can sneak up and cost you money. In this case it turned out to be just a few man days to chip and patch the exposed bars. It could easily have been a lot worse. ______________________________________________________________________________ Question:  We are constructing the reinforced concrete foundation, slab on grade and stub walls for a local elementary school project. The remainder of the building above grade is structural steel, with large-braced frames designed to meet seismic zone code requirements. The building perimeter (and most of the interior) spread footings feature anchor rod sets intended to connect large 3-inch-thick braced frame column base plates to the concrete foundation. At many locations, the steel base plates are 3 feet wide and 6 feet long. We have worked on three previous projects with this same Owner, design team and GC; all of which have been successful for each stakeholder. The key to this success has been collaboration. Our field superintendents speak with the structural engineer on a weekly basis, and our project managers show up on site for every design team job walk. There is familiarity and mutual respect among the stakeholders. ASCC Hotline callers know that ACI 117-10, section 1.1.3 specifies that a mandatory preconstruction tolerance coordination meeting be held among the various contractor stakeholders. Although contractor and material supplier attendance are mandatory, any design team and Owner attendance is optional. On our project, the structural engineer was happy to both attend and participate in the meeting. We reviewed the applicable ACI 117 tolerances for foundation concrete and ASCC Position Statement #14: Anchor Bolt Tolerances, which addresses anchor rod placement tolerances and oversized base plate holes that the steel fabricator will incorporate into the base plates on our project. The steel erector brought along a preview copy of the embed, anchor rod and column base plate shop drawings and distributed a hard copy to each meeting participant.  Review comments were invited by the steel subcontractor before making a formal submittal. During the preconstruction tolerance coordination meeting, the steel subcontractor advised that all parties should be aware of the as-built steel base plate thickness dimensions if we are going to base any of our layout line and grade using the nominal top of the steel base plate elevations shown on the construction documents as layout reference points. Because of the rather large size of the braced frame column base plates (and the project schedule), the top of each base plate will be milled at the fabrication shop, while the bottom of each base plate will be left with surfaces "as rolled" in the steel mill. In practice, this will result in base plates that could be slightly thicker than the nominal dimensions required by design. The steel detailers should show the as-built base plate thickness dimensions on the final set of shop drawings or erection drawings. In our minds, the preconstruction tolerance meeting was cordial and productive. We walked away confident we had checked all possible due diligence boxes. By and by, several pallets of 1-1/2 inch diameter anchor rods were delivered by the steel subcontractor FOB jobsite, along with setting templates made of steel plate; one template for each and every braced frame column was supplied. During the preconstruction conference, we discussed location checks conducted by licensed surveyors to verify the anchor rods were located correctly in plan and elevation. We hired a licensed surveyor to provide an initial layout and then check the anchor rod locations while the assemblies were first being tacked into place by our crew. As agreed (see below), the GC paid for the secondary survey check performed by the same licensed surveyor; conducted after all foundation reinforcing steel had been placed and inspected and after all anchor rods had been set. By the evening prior to pour day, all anchor rods had been surveyed and confirmed by licensed surveyors to be located correctly and secured, ready to receive concrete. (N.B.: During the bid process, the GC proposed to the Owner that pre-pour anchor rod location survey checks be conducted on a cost-sharing basis.  Since correct anchor rod placement is ultimately a critical path schedule activity, the GC felt it would be cheaper in the long run for the Owner to approve such an arrangement. Otherwise, we would have to carry a substantial general conditions line item to cover the risk and costs involved with potential field errors. The GC advised their thinking was that budgeting a few thousand dollars in up-front survey cost was a great insurance policy and schedule management strategy. All stakeholders and competing project bidders agreed; a Bulletin was issued by the Owner, and we all proceeded to price the job accordingly). On concrete placement day, the pour went just like clockwork. The following day, the steel erector's licensed surveyor conducted their routine as-built survey and confirmed that each and every anchor rod set had been successfully cast in concrete, within ACI 117 tolerances, at the locations in plan and elevation indicated on the construction documents. But just when we started to take a victory lap, our field crew called in from the jobsite. We had overlooked a simple detail and made a concrete placement error that became apparent at almost every braced frame column location as soon as each template was stripped. The problem?  At each braced frame column location, the engineer designed a layer of #6 top bars in each footing that sit on the bottom layers of main footing reinforcement. These top bars are labeled "U-bars" in the schematic section cut through a typical column footing, see "Section A", below. (Old-school ASCC members probably call them "hat" bars). The actual footing main reinforcement, comprised of larger #11 bars, is not shown in the section for clarity (the schematic section is way out of scale, as well).  When we stripped the templates away from each of the anchor rod sets, we could see straightaway that portions of the top U-bars did not get full concrete coverage and are partially exposed as shown in the photograph below. This condition occurs at almost every braced frame column footing location. This is a school project located in a seismic zone, and the project inspector has already reported this (with photographs) to the Owner and GC, who have expressed concern. We don't believe this will cause a remove-and-replace scenario, but we are unsure how to proceed.  Please advise how to propose a cost-effective repair plan, since we are now in danger of impacting the project schedule. caption: schematic section cut through foundation, main reinforcement not shown. caption: exposed reinforcement after template has been removed. Answer: We are familiar with the condition shown in the photograph. In this case, the bottom of each steel template was set to top of footing concrete elevation. When your field crew placed and vibrated the footing concrete, the photograph reveals that concrete never even got close to the bottom of the steel template. This predicament occurred because the template was fabricated as a solid sheet of steel with no provision for air to vent out (e.g. vent holes), or for your placing crew to visually confirm the concrete was placed to bottom of template (e.g. with "sight holes"). In other words, the concrete should have been placed right snug up against the bottom of each template, but it wasn't.  Interestingly enough, this particular condition is an unfortunate booby trap that is built into the system. In order to understand this, it is helpful to review what the ACI (American Concrete Institute) and AISC (American Institute of Steel Construction) requirements are for vent and sight holes in steel column base plates. In the ACI Code (ACI 318-19) section titled "Anchoring to Concrete", section 26.7.1(e) requires the engineer to provide the following design information in the construction documents: "Size and location of base plate holes to permit inspection and vent air when placing concrete or grout per 17.11.1.2."  (Section 17.11.1.2 apparently applies only to base plates fitted with shear lugs). The following recommendation is given in AISC Design Guide 1, Base Plate and Anchor Rod Design, section 2.10: "Grout holes are not required for most base plates. For plates 24 in. or less in width, a form can be set up and the grout can be forced in from one side until it flows out the opposite side. When plates become larger or when shear lugs are used, it is recommended that one or two grout holes be provided. Grout holes are typically 2 to 3 in. in diameter and are typically thermally cut in the base plate". So, it seems fair to say that whenever steel base plates are larger than 2 ft square, vent (or sight) holes should be provided. But nowhere in any industry documents does it imply or recommend that the corresponding templates for the base plates must be equipped with vent or sight holes to suit. This is what makes such a condition so easy to overlook during the preconstruction and construction (submittal) phases of a project. By our inspection of the structural detail and the photograph taken at the jobsite, the most sensible and cost-effective repair is to simply define the area at the top of each footing featuring exposed reinforcement, enlarge each area say 6 inches all around (as measured from the outermost edge of the exposed bars), and chip down below the bottom of the exposed bars. Propose to restore each footing top to the correct dimensions and fully encase each bar using a commercial structural repair product. Chipping depth will depend on the manufacturer's printed installation instructions (MPII) and guidance from the reviewing engineer. As it turns out, the repair area will subsequently be completely covered with a protective grout layer when you place the follow-on grout underneath each column base plate. (Note: It is our understanding that at the time of this writing, the repair procedure described above was submitted by the ASCC Hotline caller to the project licensed design professional (LDP), who has accepted the proposed repair. The concrete contractor was able to complete the repairs, stay ahead of the steel erector, and protect the project schedule). rzuellig Thu, 21 Dec 2023 18:35:00 GMT f1397696-738c-4295-afcd-943feb885714:390 https://ascconline.org/Home/News/articleType/ArticleView/articleId/389/ASCC-Alert-2-is-Issued-Pay-Close-Attention#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=389 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=389&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/389/ASCC-Alert-2-is-Issued-Pay-Close-Attention Mike Hernandez, Technical Director, The VOICE Newsletter, December 2023 ASCC just issued Alert! #2 on portland limestone cement (PLC) (members click here to view). In it, ASCC recommends two tests, one for bleed rate and one for initial set. Because reduced bleed is a common issue raised about PLC, this test was recommended, per ASTM C232. One response from experts regarding our recommendations is that even if tests are done, lab results and field results will likely be different due primarily to field environmental conditions. Similar caution on initial set time. If you have a receptive ready mixed producer both tests can be modified to higher temperature, near 90 F, and low temperature, close to 50F to provide a performance vs temperature comparison. This would be consistent with the 2012 Prescription-to-Performance (P2P) Checklist for Concrete Producer-Concrete Contractor Fresh Concrete Performance Expectations, in which target slump and air content are tested at “Hot”, 70F and “Cold” with the contractor defining anticipated hot and cold conditions. The bleed results desired are more difficult to define. Not too little with evaporation faster than bleeding so little or no bleed water. Not bleeding so much there is deep water ponding. Want that Goldilocks “just right” which can be in the 6% - 10% range for slabs or .15 - .3 lbs./sf/hr. Your feedback is welcomed.” Cement and ready mixed production have their own tolerances. The cement’s limestone content tolerance is +/- 2%. Even if the cement mill certs are near current, the result is the monthly average of daily averages so there can be day to day variability in the cement in addition to the ready mixed operationally tolerances for batch weights and admixture dosages, per ASTM C94. Ideally, your local producer will receive the cement mill certs monthly and share the results with you, their customer, so if the target cement limestone percentage increases, you will soon be aware of the increase.  There were other options considered but not recommended. Instead of just wishing members good luck, ASCC staff wanted to recommend actionable tests. A few other test options: Calorimetry – per ASTM C1753, also known as semi-adiabatic calorimetry. It is most often used to compare mixes with different dosages of admixtures or SCMs. This test was excluded because it is not a concept familiar to day-to-day performance like bleed and set time. It is the most recommended test when dealing with very challenging mix criteria and you can estimate changes in set time with calorimetry. Evaluating Plastic Shrinkage Cracking of Restrained Fiber Reinforced Concrete – ASTM C1579. This test has been used to evaluate mixes for shrinkage cracking potential. The test exposes the concrete sample to extreme evaporation conditions in a repeatable process but is only useful in mixes with a high enough water cement ratio to have adequate bleeding and cracking. PLC mixes or any mix with low bleed water would not be good mix for this test. ASCC will continue to seek best practice for our members with PLC and all low carbon concrete options. Look for the World of Concrete session on Best Practice for PLC (Type IL) on Wednesday 1/24/24 at 2:00pm. WOC Session ID: PLCWE  Topics of the presentations and discussion include: Planning for sustainable concrete construction using Type IL cement. Meeting both engineering requirements and constructability requirements. Examples from multiple projects which implemented Type IL cement. rzuellig Thu, 21 Dec 2023 18:30:00 GMT f1397696-738c-4295-afcd-943feb885714:389 https://ascconline.org/Home/News/articleType/ArticleView/articleId/377/Guidance-for-Concrete-Contractors23-in-a-Series#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=377 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=377&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/377/Guidance-for-Concrete-Contractors23-in-a-Series Jim Klinger, Concrete Construction Specialist The Voice Newsletter November 2023 Question: We are building a large, 6-story reinforced concrete parking structure with a footprint of 113,832 gross square feet (GSF). Typical slab thickness is 7 inches, post-tensioned (PT), normal weight concrete (NWC). The building geometry is such that there are very few level slabs; typically, those are located only at stair landings and elevator entrance areas. All other floor slabs are either ramps or parking slabs sloped to area drains. On past projects, we ended up getting burned because we let things sit. So, expensive lessons were learned. On this job, our field crew has stayed on top of work items typically saved for end-of-job punch lists; mostly patching, cleanup and so on. And therein lies our problem. Despite our efforts to maintain a "zero punch list" job, we were very surprised to learn that our latest monthly progress payment application has been called into question by the Owner. During a recent walk-through by the County inspector, several slab soffits were flagged due to inadequate headroom. The Owner, and now the general contractor (GC) have each taken the position that any apparent headroom problems cited in County inspection reports are solely ours to solve. We surveyed the soffits in question and agree that the as-built clearance dimensions fall shy of those required by the County parking structure building ordinance. But our as-built survey also indicates all the slabs (soffits and tops) were placed to elevations clearly indicated in the construction documents and well within ACI 117 location tolerances. We have always prepared our formwork and concrete outline drawings in-house, using detailers who have been trained to check for headroom clearances and generate preconstruction requests for information (RFI’s) if needed. But due to time constraints and the sheer size of the project, we farmed the shop drawing preparation scope out to overseas detailers, who were not instructed to perform a routine headroom check. Unfortunately, we missed this when we reviewed the outside shop drawings before we sent them up the food chain. We do not believe we are in any way responsible for meeting County code requirements when we built to design dimensions shown in our construction documents. Please advise. Answer: You are correct. Although it is always a good idea for your detailers to perform in-house headroom checks while preparing submittals, it is not your responsibility to flush out and correct design dimensions or details that could potentially conflict with building codes or ordinances. There are many ways to prove that and here are two solid industry references for your use. The first reference applies to the concrete trade and is found in Chapter 26 of ACI 318-19: Building Code Requirements for Structural Concrete. In Commentary section R26.1-Scope, we read the following: "This chapter is directed to the licensed design professional responsible for incorporating project requirements into the construction documents. The construction documents should contain all the necessary design and construction requirements for the contractor to achieve compliance with the Code. It is not intended that the Contractor will need to read and interpret the Code. A general reference in the construction documents requiring compliance with this Code is to be avoided because the Contractor is rarely in a position to accept responsibility for design details or construction requirements that depend on detailed knowledge of the design. References to specific Code provisions should be avoided as well because it is the intention of the Code that all necessary provisions be included in the construction documents". The second reference applies to all construction trades, and is found in the 2021 International Building Code (IBC), section 107.2.1: Information on construction documents as follows: "Construction documents shall be of sufficient clarity to indicate the location, nature and extent of the work proposed and show in detail that it will conform to the provisions of this code and relevant laws, ordinances, rules and regulations, as determined by the Building Official.” The Commentary to IBC section 107.2.1 explains further: "General statements on the documents, such as "all work must comply with the International Building Code" are not an acceptable substitute for showing the required information." ______________________________________________________________________________ Question: I am a structural design engineer practicing in a large metropolitan area. I am not an ASCC member, but I have a question regarding stud rails, which was the topic in the "Concrete Q&A" column titled "Placement of Headed Shear Stud Reinforcement" that appeared in the January 2022 issue of ACI Concrete International magazine. I just received an urgent call from the Owner's inspector at the jobsite. Here it is, the end of the workday, and the concrete contractor is scheduled to place slab concrete first thing tomorrow morning. During today's inspection, it was revealed that there are stud rails that were not installed at a few columns when the bottom reinforcing steel layers were placed due to supply-chain issues. The contractor has now installed the missing stud rails in the "upside-down" configuration described in the ACI Q&A. I have no problem with that, since the stud itself does not care which end is up. In the ACI Q&A Fig. 1, however, the exact configuration that the contractor has placed is not depicted e.g., an upside-down assembly with only one forged stud anchor head (at the bottom) and no head at the top (but shop-welded to a continuous steel base rail). The project inspector is saying that, since the work in place does not match ACI Q&A Fig.1 exactly, the installed assembly is questionable and is looking to us to provide engineering approval before concrete can be placed. Please advise. Answer: We must assume here that the stud rail assemblies in question were inspected in the fabrication shop and all materials and welding were found to be in compliance with the requirements given in ASTM A 1044: Standard Specification for Steel Stud Assemblies for Shear Reinforcement of Concrete. According to ACI 421.1R-20: Guide for Shear Reinforcement for Slabs section 1.1, "To be fully effective, the anchorage should be capable of developing the specified yield strength of the studs. The mechanical anchorage can be obtained by heads or strips connected to the studs by welding. The heads can also be formed by forging the stud ends." In other words, a headless stud end welded to the steel base rail is a dual-purpose mechanical anchorage and spacer that is interchangeable with an anchor head forged in the manufacturing process. It appears, then, that the stud rail assembly installed in the field should be acceptable as long as the quality control inspection requirements described above have been met. ______________________________________________________________________________ Question: We are preparing a bid proposal for a large steel structure featuring 26 floors worth of composite concrete slab on metal deck (SOMD). This will be a hotly contested bid among the competitors here in our local market, partly due to the Owner's reputation for disbursing progress and retention payments in a timely manner. Since the building footprint is approximately 44,000 GSF, we estimate we can complete each floor in two placements of 22,000 SF each, which translates into two 375 cubic yards (CY) pours per floor. The construction documents indicate the steel beam and metal deck soffits are to receive a follow-on spray-on fireproofing application. The metal deck specifications call for the metal deck to be vented. These two details, taken in combination, represent potentially significant cost items that could make our price non-competitive if we include them. How should we approach this in our estimate and proposal letter, so we don't get left holding the bag? Answer: Even though this is a private job, we believe the best course of action is to write a pre-bid RFI that (in theory, anyway) should be answered by the design team and distributed via a Bulletin to all bidders and stakeholders before bid day. Assuming you stick to your 52-pour placement plan, you could be looking at up to 104-man days’ worth of spraying the soffits and steel beam substrate with water and dragging visqueen around underneath the slab area to catch the drippings during and after each pour. You can also guarantee receiving that friendly call or email from the GC telling you that you missed a few spots and now the fire proofer is refusing to install his work until you rent a scissor lift and commence to scrubbing cement paste that leaked through the vents in the metal deck. When you craft your pre-bid RFI, attach a copy of Technical Note TN.4 Venting of Composite Steel Floor Deck prepared by the Steel Deck Institute, which explains why some specifiers erroneously believe letting the cement paste and water slurry drip out of the bottom of structural decks will help the concrete dry out faster. It doesn't. Advise the design team that--if the deck venting really is desired--the Owner should carry a budget allowance to cover all labor and equipment costs associated with cleanup of the leakage. This way, all bidders will be pricing that portion of the work on a level playing field. If the Owner requests a ballpark estimate to help establish the allowance amount, you could start by quoting what 104-man days plus water and equipment rental is worth, and that should discourage any unnecessary dollar leakage right then and there. The Steel Deck Institute's Tech Note TN.4 is available at no cost. ______________________________________________________________________________ Question: We just returned to our trailer from the preconstruction "meet and greet" project kickoff meeting. Our formal concrete pre-pour conference is still a month out yet. Today's meeting included the Owner, the design team, the GC, and the inspection agency representative. This project features a large footprint framed in structural steel with large expanses of LWC on a metal deck. Access to the jobsite is limited, and logistics dictate that we must stage our concrete pump at one end of the site and pump from there using up to 200 feet of pump hose system. During the meeting, there was much discussion commensurate with a LWC SOMD scope...the importance of adequate amounts of lightweight aggregate pre-soaking, slab finish expectations, and whether or not the Owner wants to consider covering the premium cost for us to provide temporary steel beams in lieu of us pouring to a constant gauge slab thickness. All parties were on the same page until the inspection agency representative stated they would not allow the cement slurry we use to prime our pump line system to be incorporated into the pours. In other words, we would have to prime the pump and collect the slurry into debris boxes up on the metal decks- which opens a costly, logistical can of worms with potential safety concerns. Until now, neither the structural engineer nor the Owner had even been aware of this. Now they have expressed concerns about potential side effects. Please advise. Answer: Since your pre-pour conference is a month away, here is one suggested course of action: have your ready-mix supplier prepare an engineered pump primer mix design (as described below) with appropriate backup and submit a preview copy "to be discussed at the upcoming pre-pour conference." In the meantime, consider the following background information. The concept of using a lubricating cementitious primer is described in several ACI documents with differing points of view. The Owner's inspector is probably basing his position on ACI 311.7-18 Specification for Inspection of Concrete Construction section 3.2.4, which instructs the concrete inspector to "Verify that grout used to lubricate the pump hose is not incorporated into the placement." In the case of shotcrete, ACI 506R-16 Guide to Shotcrete section 4.3 tells us, "initially, the material hose will be lubricated with a primer. The primer lubricates the line ahead of the initial plug of concrete and can be a water cement slurry or prepackaged material. The nozzleman will direct the nozzle away from the work until the primer has been completely discharged." On the other hand, a lubricating cementitious primer labeled by ACI as a "rich grout pre-charge" is described in ACI 543R-12: Guide to Design, Manufacture and Installation of Concrete Piles section 8.6.5.1 when using conventional concrete as follows: "it is frequently specified that a small batch of rich grout (generally one part cement and two parts concrete sand and water) be placed in the pile immediately before the concrete placement. The purpose of the grout is to partially precoat the pile sides and reinforcement with a mortar mixture and supply a charge of rich cement grout to the top of the pile to counteract the segregation of coarse aggregate at the pile tip during the initial charge of concrete." Translation: It is perfectly fine to prime the cylindrical sides of a structural concrete pile with a cementitious slurry and then leave the primer in place as part of the finished work. On one recent and noteworthy high-rise project, a pump primer mix design was proportioned similar to the ACI 543R pile slurry mix described above-12 sacks of ASTM C150 cement (1128 lbs.) and 2390 lbs. of ASTM C33 concrete sand- essentially in a 2-to-1 proportion. For water, 50 gallons was proportioned to provide a slump range of 8 to 11 inches, which makes the slurry easy to spread out over a large area of the deck. Trial batches of the pump primer yielded 28-day compressive strength of 7520 psi and 56-day compressive strength of 8250 psi. We rarely see LWC specified for use in composite metal decks with design strength above 6000 psi. Preparing and submitting an engineered primer mix design with appropriate backup should go a long way toward convincing the structural engineer to accept the pump primer incorporated into the work. rzuellig Wed, 22 Nov 2023 16:01:00 GMT f1397696-738c-4295-afcd-943feb885714:377 https://ascconline.org/Home/News/articleType/ArticleView/articleId/376/ASCC-Continues-to-Increase-Impact-at-ACI-Convention-in-Boston#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=376 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=376&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/376/ASCC-Continues-to-Increase-Impact-at-ACI-Convention-in-Boston Mike Hernandez, Technical Director The Voice Newsletter November 2023 ASCC members continue to work on numerous ACI Committees to monitor and influence the documents and present the contractor’s position. There are ACI committees on nearly any subtopic in concrete you can imagine. ASCC/ACI members have provided feedback on the work happening in the committees in which they are involved. For reference, I have added an asterisk (*) to the ten ACI committees which had the most ASCC contractor voting members in June of 2023 when the latest ACI Committee Membership list was compiled. The following includes the ASCC/ACI top ten with several added when substantial member feedback was provided. 117* - Tolerances: Continued to ballot revisions to 117-10(15). An impassioned request by an ASCC Member to include ASTM plastic concrete tolerance information so that contractors could reduce the quantity of documents they need won over the room. The information will be maintained and expanded to include more ASTM information. Subcommittee L-Laser Scanning Chair Leo Zhang with Conco said “117L subcommittee is working on a technote to provide the readers with some basic information about laser scanning for concrete.” 134* - Concrete Constructability: Hosted a session titled “Prescriptive or Performance? What is the State of the Industry and What are the Examples of a Positive Movement Towards Collaboration?” The committee also had a mini session on “Type IL Cement, A Step to Reducing Overall Global Warming Potential”, which included presentations from ASCC Members Jason Wimberly with Lithko Contracting, David Venegas with Vemac, Boyd Clark with CTL Group and co-moderators Keila Lombardozzi with DPR and Brian Carson with Nexgen Contractors. Attendees reported a packed room with 200+ people. 301 - Specifications for Concrete, Anthony DeCarlo with Dominion Concrete Services stated “301 will be adding an optional sustainability section to the document when the new 301 document is scheduled to be published in 2026.” Currently, the new language for this section is being worked on. Continued work on resolving negatives regarding revised or new language for each section of the specification document. Subcommittee S-Sustainability, Eamonn Connolly of McHugh concrete reports that there was a presentation by Colin Lobo of NRMCA on their new Carbon Budget Calculator. NRMCA and ASCC agree that total carbon budgets should be used instead of trying to reduce the CO2 emissions in every mix an equal percentage. Mr. Connolly added that there was discussion of life cycle analysis, in particular A5, construction stage emissions. ACI, PCA, NRMCA and ASCC are attempting to collect A5 data and are requesting member support for this initiative. 302* - Construction of Concrete Floors: Reviewed joint 302-ASCC survey results. It was standing room only with several hundred people in the room. Joe Neuber of Neuber Concrete commented, “My recollection of the meeting was the discussion on Type IL cement and the problems that the industry is having with the floor slabs throughout the country. Depending on what part of the country you are from seems to dictate the degree of issues encountered. There seems to be a lot of discussion concerning the different types of issues that the industry is encountering. It was generally agreed that there needs to be a standard for material. Amount of limestone in the Type IL and the fineness of the materials around the country. The general overall agreement is that in slabs on ground (especially ones poured out in the weather) have little or no bleed water and this is causing the top surface to dry and be ready to finish long before the mass of the concrete is ready which in turn causes surface defects, delamination, and shrinkage cracking.” 310* - Decorative Concrete: Chair Clark Branum with ASCC states, “committee was well attended, we spent most of the time resolving comments from chapter 6 on staining. We voted to accept several changes and adopted the new version of the chapter.” Clark’s term as 310 Chair has been extended by a year to April 2025. 310 0J* - Polished Finishes: Clark Branum with ASCC said, “A lot of the 310-OJ meeting was spent on a presentation on diamond tooling by Boride engineering. I’m working on a classification for polished concrete floors to submit to 302.” 330* - Concrete Parking Lots and Site Paving: Chair Jason Wimberly with Lithko Contracting stated, “330 is just completed responding to TAC comments on the SPEC. 330 will be hosting two mini sessions at the upcoming convention in New Orleans. The first session will present the data and a discussion of results from testing on multiple VEMAC projects to understand the impact on thermal swings to concrete slabs and pavements (hint: it is much more significant than previously thought and a likely culprit to many problems experienced by contractors daily). The second session will be the presenting of data from the full-scale field trials using four same-source Type I/II and Type IL cement concretes in SOG/Panels/Pavements in the Denver, CO market. Many concerns voiced by contractors have been quantified when able to conduct work in a full-size trial against previous Type I/II cements.” 347* - Formwork for Concrete: Continue to ballot new 347 specification document. Eric Peterson with Webcor reported that the 237-self consolidating concrete (SCC) committee is forming a joint innovation task group between its committee and 347. The joint task group is going to look at formwork pressure. Current guidance is assume full liquid head, which makes for long placing durations or robust formwork. SCC field testing indicates the real value is much lower. 360* - Design of Slabs on Ground: David Buzzelli with Texas A&M Concrete said “worked on resolving negatives.” CLC* - Construction Liaison Committee: Reports from members on the activities of ASCC, TAC, EAC, PRO and ACI committees, which affect concrete construction. CLC is provided access to documents under TAC review for input. ASCC technical staff reviews as many as we can. A new ACI academic construction journal is being proposed to the ACI Executive Committee. If approved, they will be looking for an industry advisory board to participate. This is for university level school of construction management professors to have peer reviewed documents. E703* – Concrete Construction Practice: Chair Kevin Hanson with Baker Concrete reported, “E703 is currently completing editorial review of the revised CCS-1 Slabs on Ground for eminent submission to the Educational Activities Committee. We are currently recruiting new members, specifically those with experience in decorative concrete, to champion an upcoming update to CCS-5 Placing and Finishing Decorative Concrete Flatwork.” 90-07* TAC Productivity & Constructability: First meeting was recently to discuss review of code documents. Members volunteered to review documents expected to be submitted to TAC this fall or spring 2024. ACI Board of Directors: Anthony DeCarlo with Dominion Concrete Services reported, “New executive vice president Fred Grubbe was introduced to the board. Discussed the results of the P&D session regarding goals set forth in the ACI Outlook 2030. The Board approved a program to certify ACI fiber reinforced polymer reinforcing bar inspectors. Approved budget for fiscal year 2024.” ACI Excellence Awards Gala: Congratulations to McHugh Concrete Construction for 2nd place in high-rise structures (over 15 stories) for The Reed at Southbank, Chicago, IL. ACI PRO Contractor’s Day Lunch: Dan Baker, Founder of Baker Concrete & Jeffrey Coleman with Coleman & Erickson hosted a discussion on the lack of communication between designers and contractors. One take away about resolving issues with open communication instead of pursuing legal action by Mr. Baker was “you don’t sue the man you go fishing and hunting with.” ACI PRO/ASCC Reception: Ceco & Conco have joined PRO and several other ASCC members have expressed strong interest. ASCC and ACI PRO held a joint reception at the conclusion of PRO day at the Convention, and it was very well attended. Photo with Ray Hefner, ASCC Executive Director, greeting Charles Nmai, with Master Builders Solutions and ACI’s 2022-2023 President, is below. Rick Yelton with World of Concrete is in the background. rzuellig Wed, 22 Nov 2023 15:58:00 GMT f1397696-738c-4295-afcd-943feb885714:376 https://ascconline.org/Home/News/articleType/ArticleView/articleId/369/Guidance-for-Concrete-Contractors-22#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=369 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=369&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/369/Guidance-for-Concrete-Contractors-22 Jim Klinger, Concrete Construction Specialist The Voice Newsletter October 2023 Full disclosure: Sometimes it takes a bit of background confected with lore borrowed from other structural building trades to help illustrate obliquities particular to our own concrete trade. As it turns out, this right here is a classic example of that. To oversimplify enormously, any time a licensed design professional (LDP) prepares the structural design of a steel building frame featuring composite concrete slabs on metal deck (SOMD), reference documents (e.g., applicable building codes) from local or regional jurisdictions and at least 4 national governing standard organizations are generally consulted as follows: The American Institute of Steel Construction (AISC), whose Code and Specifications govern the design, fabrication, erection, and retrofit of structural steel columns, beams, and other shapes. The Steel Deck Institute (SDI), whose Code and Standards govern the design, sale, purchase, manufacture, and installation of composite steel deck-slabs (aka "slabs on metal deck" aka "SOMD"). The American Welding Society (AWS), whose Codes and Standards govern the design, prequalification, and inspection of all welds, including welded splices of certain grades of reinforcing steel and headed steel studs. The American Concrete Institute (ACI), whose Codes and Specifications govern the design of most structural concrete, including slabs on metal deck when specifically called out as "reinforced concrete" (ACI 318-19, section 1.4.10). Armed with this modest library of background information, we can now view the first of this month's ASCC Hotline topics through a custom lens...call it adjusted for perspective...and down into the rabbit hole we go... ______________________________________________________________________________ Question: We are a concrete subcontractor working on a 20-story high rise project featuring structural steel framing and unshored composite slabs on metal deck (SOMD). As of today, our portion of the project work is approximately 5 percent complete. All steel framing, metal decking, reinforcing steel, and construction joints are furnished and installed by others. Our subcontract work was bid as a discrete "P-P-F" scope (pump-place-finish only) which actually also includes ready mix concrete purchase and one application of spray-on curing compound before our finishing crew leaves the jobsite. As can be seen below in our bid proposal line item #22, we also include blow-off of the metal deck substrate prior to concrete pours: [Based on several unsavory and very costly experiences on past SOMD projects, our company bid policy now dictates that we call special attention to--and exclude--handling any debris generated by the Division 5 trades simply due to the sheer weight of the debris (steel is more than 3 times heavier than concrete) and the awkward logistics required to collect and transport such heavy spoils to dumpsters, usually located on the ground.] Since we are not mobilized on site full time, a typical SOMD placement operation actually starts for us just after lunch on the day before we are scheduled to place concrete. We dispatch our finisher foreman and a small crew to walk the pour area with the general contractor (GC) representative to discuss logistics and expected slab finishes, review survey results (survey performed by GC personnel) showing the as-built elevations of the metal deck and structural steel substrate, set our finishing screed pins (we generally place SOMD to a uniform gauge thickness and state as much in our bid proposals) and begin our pre-pour clean up. And it is the cleanup part where--despite our bid exclusions highlighted above-- things can still get messy. When we begin our pre-placement walk-through, the work is still in progress. Electricians are running conduit, plumbers are setting cans, sheet metal workers are framing metal deck blockouts, ironworkers are placing rebar, and so on. By all rights, these trades should be 100% complete by the end of the day, including cleanup of all trade-specific trash and debris each trade has generated. In theory, the inspector should be able to complete the pre-pour checklist in reasonably comfortable fashion. Unfortunately, in the concrete business, things happen. Concrete activity durations leading up to a placement can become squeezed, causing our cleanup crew to end up being chased by the concrete bucket. And just when we thought we had the whole routine outsmarted. To make a long story short, here is the reason for this Hotline call. The Owner's inspector usually assigned to our project was out on leave. On his inspection watch, removal of broken ferrules by the metal decker after the studs are inspected is a strictly enforced checklist item that must be completed before he will allow rebar placement to proceed. But the replacement inspector informed us that the broken ferrules did not need to be cleaned up at all. In other words, the inspector told our cleanup crew to just go ahead and let the broken ferrule pieces be incorporated into the slab concrete as long as the ferrules were spread out and not grouped into piles on the deck. All other debris, however, had to be cleaned up as before. [N.B.: In theory, headed studs (aka "shear connectors") can be fillet welded via traditional arc welding to the top flange of a steel beam to ensure the steel beam/metal deck/concrete SOMD truly act as one composite structural unit. But fillet welding is too slow. Instead, the studs are shot through the metal deck and fused to the top of the steel beam flange supporting the deck. In that case, special vented ceramic through-deck ferrules (aka "arc shields") are placed at the bottom of each stud. The refractory properties of a vented ceramic ferrule allow the weld metal to be contained while at the same time allowing zinc and other contaminants produced by melting the galvanized metal deck to escape the weld puddle zone at the base of the stud. Once cooled, the ferrules are broken off to allow visual inspections to verify a full 360-degree weld flash and allow subsequent hammer/bend testing to proceed. The broken ceramic pieces can then be collected and discarded. In theory, of course. See photograph below showing shot-on studs, sheet metal decking material, and broken ferrules.] photo credit: Sino Stone. Note contaminant exhaust vent pattern at base of stud. So that is how it went until yesterday--a pour day--when the original inspector returned to work and saw the metal deck substrate littered with broken ferrules at the same time our crew was assembling the last sections of pump system. In order for the inspector to allow the pour to go forward, the GC paid our crew to clean up the broken ferrules. We can only assume the GC then passed the cost on to the metal decker via a backcharge. So, the Hotline question then becomes..."Which inspector has it right?" Going forward, we don't want to get caught up in last-minute labor scrambles to mitigate cleanup responsibilities owned by a division 5 trade. Answer: The Owner's replacement inspector is correct. According to the latest governing SDI document (SD-2022 Standard for Steel Deck, page 90), broken ceramic stud weld ferrules can remain on the deck and be incorporated into the pour for reasons stated in section J3 below: This is a great example of Division 5 cleanup line items that really need to be included in bid proposals and preconstruction meeting agendas on every SOMD project. Thanks to ASCC member Chris Garcia of DPR for helping to research this issue. _____________________________________________________________________________________________ Question: We are in the preconstruction submittal phase of an above grade, mid-rise reinforced concrete office building project under private ownership. This is no exposed architectural concrete masterpiece headed for the winner's circle at the ACI Excellence in Concrete Construction Awards Gala. This is a simple concrete box where--once in service-- all the concrete surfaces will actually be concealed by the work of follow-on trades. We're talking about dropped ceilings, tiled floors, furred columns, and a curtain wall skin. When we made our first round of reinforcement placing drawings, we attached a companion submittal package that included the manufacturer's cut sheets for all the standard reinforcing steel accessories we routinely use in our construction market e.g., tie wire, slab spacers, beam bolsters, bar chairs and precast concrete dobies. The architect rejected the use of the dobies on the grounds that the following project specification allows only metal or plastic rebar support material to be used in the work: We could not find an ASCC Position Statement that addresses this topic. Is there anything in the ASCC Technical Division library that we can use to argue that the precast concrete dobies should be accepted? Answer: There are several arguments that could be made to support your case, especially if the sole reason for rejection is "just because" it does not meet the specification without any further explanation or qualification. (We understand that the architect did offer the explanation that no one in their office had ever seen dobies used on past projects.) First, the project specification does not say that precast concrete dobies cannot be used. Second, by simple reference elsewhere in your Division 3 specifications, the work in your concrete scope is governed by ACI 301-20: Specifications for Concrete Construction, section 3.2.1.8: Reinforcement Supports, which states "Provide reinforcement support types within structure as required by Contract Documents. Reinforcement supports shall conform to CRSI RB4.1." (N.B. The Concrete Reinforcing Steel Institute (CRSI) document referenced above is RB4.1-2022: CRSI Standard for Supports for Reinforcement Used in Concrete, which states in section 1.1.1 "This specification covers the design, use, material, and minimum performance requirements of reinforcement supports used in concrete to support various types of reinforcement, including but not limited to plain and deformed reinforcing bars, prestressing steel, post-tensioning tendons, steel wire and plain and deformed steel welded wire reinforcement." As it turns out, precast concrete dobies are manufactured in all shapes and sizes, many of which are displayed and discussed in RB4.1. In similar fashion, the CRSI Manual of Standard Practice defines "Dobies" in a roundabout way as follows: It should be a simple matter, then, to demonstrate to the design team that the use of dobies is in fact an accepted standard concrete industry practice. Given the fact that the concrete surfaces on your project will always be hidden, it should not be difficult for the architect to reverse the call and accept your proposed use of dobies. Here at the ASCC Technical Division, we have seen cases where dobies may not always be the best choice of bar support. We have seen dobies crushed under the weight of heavy mat slab reinforcement, which usually doesn't occur until the outermost layer of top bars are being placed, and by then it's too late for an easy fix. We would also stay away from the risk of using dobies in architectural concrete work, especially when the design team has specified the bar supports reasonably well in this example specification: ______________________________________________________________________________ Question: We are working on a pump-place-finish only (P-P-F) project where we carried the cleanup of pour areas prior to concrete placement in our bid proposal. By the time we mobilize on the jobsite, all the reinforcing steel has already been placed and secured by others. It is then up to our crew to pick up sawdust, loose trash, and debris through the layers of rebar; either with a backpack vacuum or some kind of home-made device (e.g., "a chingaderas") invented on the spot to snag those hard-to-reach items. We find ourselves fighting a constant battle with the inspectors regarding the debris generated by the reinforcing steel subcontractor, namely the rebar bundle tags and tie wire clippings. Is there anything in the industry literature that talks about who has ownership of such specific (e.g., not miscellaneous) trade debris? We know, for example, that painters are responsible for catching their spoils with a drop cloth they bring with them to the work. Is there a similar analogy that applies to the rebar trade? Answer: This question is a perennial favorite here at the ASCC Technical Division. In our many years working with concrete, we have only found one "industry literature" mention of the tie wire clipping issue, namely in the textbook by Smith and Hinze titled "Construction Management: Subcontractor Scopes of Work" (CRC Press, Boca Raton, Fla., 2010). The following excerpt appears in Chapter 6- Reinforcing Steel: A few years ago, we contacted the Concrete Reinforcing Steel Institute (CRSI) and asked them to weigh in on the question, "Who owns cleanup of rebar bundle tags and tie wire clippings?" The CRSI response was that there was nothing committed to print, but the accepted practice is for ownership of trade-specific cleanup items to be clearly addressed in contract scope language on a project-by-project basis. We have seen many rebar proposals, for example, where the rebar bidder assumes the cleanup of tie wire clippings due to normal rebar installation is excluded. Since there is no mention of the bundle tags in the proposals we reviewed, we believe that particular cleanup responsibility lies with the trade that cuts the bundles loose and generates the tags as debris e.g., the rebar installer. We did hear of one instance where the tie wire clipping issue was the cause of jobsite arguments sufficient enough to bring the project owner to the table. The owner's inspector was demanding that all tie wire clippings be removed from the pour area before concrete could be ordered and placed. Both the concrete and the rebar subcontractors were refusing to clean up the clippings. To break the stalemate, the owner was told by one of the parties that the wire clippings actually constitute the addition of steel fibers into the concrete mix, a substantial benefit that was being generously supplied to the owner at no extra cost. Once the condition was reframed as a freebie, the owner agreed and settled the issue straightaway. Full disclosure: Sometimes it takes a bit of background confected with lore borrowed from other structural building trades to help illustrate obliquities particular to our own concrete trade. As it turns out, this right here is a classic example of that. To oversimplify enormously, any time a licensed design professional (LDP) prepares the structural design of a steel building frame featuring composite concrete slabs on metal deck (SOMD), reference documents (e.g., applicable building codes) from local or regional jurisdictions and at least 4 national governing standard organizations are generally consulted as follows: The American Institute of Steel Construction (AISC), whose Code and Specifications govern the design, fabrication, erection, and retrofit of structural steel columns, beams, and other shapes. The Steel Deck Institute (SDI), whose Code and Standards govern the design, sale, purchase, manufacture, and installation of composite steel deck-slabs (aka "slabs on metal deck" aka "SOMD"). The American Welding Society (AWS), whose Codes and Standards govern the design, prequalification, and inspection of all welds, including welded splices of certain grades of reinforcing steel and headed steel studs. The American Concrete Institute (ACI), whose Codes and Specifications govern the design of most structural concrete, including slabs on metal deck when specifically called out as "reinforced concrete" (ACI 318-19, section 1.4.10). Armed with this modest library of background information, we can now view the first of this month's ASCC Hotline topics through a custom lens...call it adjusted for perspective...and down into the rabbit hole we go... Plain dobies (no tie wire)                                       Dobies with tie wire rzuellig Mon, 30 Oct 2023 17:32:00 GMT f1397696-738c-4295-afcd-943feb885714:369 https://ascconline.org/Home/News/articleType/ArticleView/articleId/368/Concrete-Strength-by-the-Maturity-Method#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=368 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=368&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/368/Concrete-Strength-by-the-Maturity-Method Mike Hernandez, Technical Director The Voice Newsletter October 2023 The maturity method for estimating in place strength of concrete has been around for decades. It is useful for timing the start of post-tensioning unbonded cables and for removing formwork under elevated decks. A concrete mix can be correlated to make a time-temperature strength curve. This is quite helpful in the winter months when in place strength could be substantially different than the cylinders taken on pour day and stored in a curing box at 60F to 80F or even from field cured cylinders because the cylinders have far less mass than the structure so they will generate less hydration heat. Recently, the maturity method is being used to optimize saw cutting of slabs on grade. Contractors are trying to hit the Goldilocks window of just strong enough to not ravel the sawcut edges yet fresh enough that random shrinkage cracks are not developing yet on Type IL cement concrete mixes. Knowing early age strength is a helpful tool. My experience using maturity probes dates back to the early 2000’s. The team was placing elevated decks in Denver Colorado, from December - March while heating the formwork enclosed from below. A strength to maturity relationship or maturity index had been developed that fall using ASTM C1074 by the testing lab. They needed 15+ cylinders and a few maturity probes. With a strength to maturity relationship, our team could figure out the approximate strength of the concrete at any given time. It was a balmy 70F under the tented and heated decks that winter. Each morning and afternoon I would go out and attach a reader to the wires sticking out of the deck, which were connected to loggers inside the concrete. The maturity probes provided feedback on the current temperature and degrees C-hours number, which correlated to a given strength. Once all the probes had crossed the minimum threshold, stressing of post-tension cables began. Without the reassurance of the maturity index, it is unlikely the engineer of record, GC or owner would have allowed us to stress PT and a few days later strip decks so quickly in the dead of winter. ACI 318 and CSA A23.1 both reference this strength evaluation method in accordance with ASTM C1074 as do 30+ state departments of transportation. NRMCA Technology in Practice #15 “Estimating Concrete Strength using Maturity” is a useful resource. By the 2010’s, radios were added to the same equipment and types of probes, which were used to monitor the temperature on hundreds of mass concrete placements our team had in bridge substructures. ACI and FDOT set limits on maximum temperature and differential between the core of the concrete and the surface. Temperature probes are the only effective way to track and record this data. Part of the challenge was to monitor the temperature every 8 hours to meet the specification and know if thermal control concrete blankets needed to be added or could be removed. With the radios in the system, we could connect to a computer brought within 300’-500’ of the probes. Still had to drive on site close to midnight, but it was better than manually plugging wires into a handheld reader. Several years ago, the wires were deleted and replaced by Bluetooth capable devices, simplifying their use even more. Lifting tilt up panels in winter, we collaborated with our ready mixed supplier and had maturity devices in the last panels placed prior to erecting. The probes confirmed the panels were stronger than the field cured cylinders. and we were confident to start lifting. The introduction of Type IL cement concrete or Portland Limestone Cement (PLC) concrete into ~40% of all concrete purchased in the U.S has required contractors to consider a few more things. Contractors will need to rerun maturity index strength curves using PLC mixes, they are no longer valid for maturity curves developed using I/II cement. From discussion with many contractors, the acceptance cylinders with IL cements seem more sensitive to poor initial curing than the I/II mixes. Having probes in the concrete could resolve slow and expensive disputes about in place concrete strength. Many contractors are reporting lower early age strength compared to older I/II mixes. Using the maturity method will help keep schedules on track by being able to monitor strength continuously, not just when cylinders are broken. Regarding saw cutting, the US Federal Highway Administration (FHWA) has a free software HIPERPAV to look at early age strength of concrete to time the cutting of control joints. Combining this with maturity probes can assist contractors doing paving work and large slabs on grade. This is one more tool to have in the box of options when trying to be a productive ASCC contractor. rzuellig Mon, 30 Oct 2023 17:30:00 GMT f1397696-738c-4295-afcd-943feb885714:368 https://ascconline.org/Home/News/articleType/ArticleView/articleId/358/Guidance-for-Concrete-Contractors-21#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=358 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=358&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/358/Guidance-for-Concrete-Contractors-21 Jim Klinger, Concrete Construction Specialist The Voice Newsletter September 2023 Question:  We were recently awarded the subcontract for a reinforced concrete high-rise tower that features 3-ft thick shear walls with moderate to heavy reinforcing steel congestion. The shear walls in some sectors are up to 4-ft thick. This upcoming project has a fast-track schedule, the so-called "3-day cycle" that has become popular with Owners here in our regional construction market. Based on our experience with similarly congested shear walls, we expect that even with self-consolidating concrete (SCC) there will be honeycomb (rock pocket) conditions that will require timely repair and patching. The following statement appears in our construction documents: "The Contractor is responsible for correcting work that does not conform to the specified requirements, including strength, tolerances, and finishes. The Contractor shall submit the proposed solution for review and approval."  Several brand-name materials that are fair game for concrete repairs and patching are called out in our Division 3 specifications along with this qualification: "Use repair products in accordance with manufacturer's recommendations". For our project, such repair materials are required to meet ASTM C1107: Standard Specification for Packaged Dry, Hydraulic-Cement Grout (Non-shrink). During the preconstruction collaboration conference specified in ACI 301-20, section 1.6.1, all parties recognized the fact that our proposed repair submittals will have to be prepared, reviewed, and approved quickly in order to avoid schedule hiccups. Since most of the repairs will involve seismic shear walls, the structural engineer wants to review each and every proposed repair on a case-by-case basis. All stakeholders present at the conference (e.g., the concrete contractor, the general contractor (GC), the licensed design professional (LDP), and the Owner's testing and inspection agency) each committed to drop back and develop plans intended to accommodate expedited schedule impacts affecting each stakeholder's respective scope of work. In addition to the proposed repair location and material submittals, the GC asked us to provide in our submittals a list of tests and inspections that the Owner's test agency will need to arrange based on the size of the repair and the type of materials we propose to use in each case. In other words, we have been asked to create an advance repair submittal "template" that is intended to help streamline the repair process. (N.B.: Although testing and inspection responsibilities are not included in our contract scope, we did not balk at the GC’s request to help predict the work of others in our submittals. For us, such requests are actually routine, especially for large concrete projects.  It would not be at all unusual, for example, to be asked after the contract award how many cubic yards (CY) and how many pump or shoot days we estimated during our bid logistics and schedule analysis. This information helps the Owner solicit bids from the testing agencies, who cannot reasonably know at bid time how we intend to build the job.) For the most part, simple rock pocket repairs (e.g., within a few inches of the face of wall) are easy enough for us to accomplish.  It is the deeper pockets and voids behind the congested reinforcing steel bars that are at issue. We understand why the Owner wants us to help forecast the testing and inspection scope (there is no way the test agency can forward-price such undefined scope), but therein lies the rub.  Each of the specified repair material options comes with its own unique MPII, some of which is based on unpublished "proprietary" support data. This makes it difficult for us to prepare repair material and procedure submittals in advance, let alone try to forecast the testing and inspection scopes with any degree of accuracy. We checked in our latest ACI Manual of Concrete Practice (MCP-2015) for guidance related to construction grout applications but were unsuccessful. Can ASCC provide any information that will help us prepare the construction grout repair submittals described above? Answer: Your question involves just a limited portion of the many possible uses a concrete contractor may have for so-called "construction grout".  Since "grout" is such a wide-ranging yet curiously arcane topic, the discussion below does not include these typically used grout applications: unbonded post-tensioned (PT) stress pockets, bonded PT tendon ducts, precast concrete connections, masonry grout, auger cast piles, pile reinforcement anchorage, and so on.) But strangely enough, while we have excluded discussion of many grout applications above, we find that the best way to assist in your case is to discuss a totally separate construction grout application that almost every concrete contractor knows full well: grouting of steel column base plates.  In other words, it's kind of the same thing...only different. Any time you have a structural steel building marrying up with a reinforced concrete foundation, there is one structurally significant grout application that has (to date, anyway) not yet been addressed in building codes- including ACI 318- and that is the grout placed under steel base plates. So, you are correct in noting that any guidance regarding base plate grouting and its associated testing and inspection activities are difficult to find. It is our understanding that this issue is currently under advisement in various ACI 318 Code subcommittees, and incorporation of guidelines for certain grout applications, including testing and inspection requirements, may be available on the near horizon. Generally speaking, base plate grout is given little attention in structural construction documents. "General Notes" sheets, for example, often devote only one or two lines that appear as follows for material: And as follows for inspection and testing: Because so little information appears in the construction documents, who then is responsible to determine the materials, placement procedures, testing requirements, and inspection protocols? Is the concrete contractor the one who is responsible for interpreting the individual MPII from each manufacturer? One thing is for sure, when the concrete contractor is presented with such limited information, there are many questions that can (and should) be presented to the LDP via Requests For Information (RFIs) straightaway as follows below. Such RFI questions apply whether the scope is steel base plate grouting or structural repairs in a concrete shear wall. And all of them are the responsibility of the LDP to answer. What is the compressive strength of the grout required, and how (and when) will that be determined? Should the inspector mold 2-inch square cubes...or 4-inch diameter cylinders? How many samples should be cast? Are the samples to be field cured or lab cured? (Typically grout cubes can break up to 10 to 15 percent higher than companion cylinders cast at the same time.) Does testing of unconfined cubes or cylinders accurately represent the in-situ grout strength in its highly confined condition? Is destructive testing the only truly reliable way to determine the strength of grout under a steel baseplate? And even more to the point, is it possible or feasible to extract core samples in the case of suspect test results? What grout consistency is required? Depending on the amount of water added, the material could range from plastic (e.g.,"dry pack") to flowable to fluid. Who is responsible for monitoring the amount of water added to the site-mixed powdered grout? Will all of the proportioning, mixing, curing and other procedures prescribed in ASTM C1107 be followed?  If you are familiar with this ASTM Standard, have you ever seen such procedures carried out on your project when your crew is grouting column base plates or patching a shear wall? For concrete, there is usually a batch-to-placement (BTP) time limit specified by the LDP. Is there such a "shelf-life" time requirement for grout placement?  For "non-shrink" grout, will the inspector really be casting and testing shrinkage bars? Should a pea gravel "extension" be introduced into the mix?  Most grout MPII requires such an extension whenever the grout layer thickness exceeds 3 inches. What tests and inspections are appropriate when pea gravel extensions are added? At concrete batch plants, for example, addition of water and other constituents are carefully measured and closely monitored using calibrated equipment. Can a similar Quality Control standard of care be expected in the field? (N.B.: According to several grout manufacturers of MPIIs, the addition of aggregate to the mix is not done for reasons of strength. The pea gravel aggregate is actually introduced to act as a heat sink to cool the grout section when the proprietary cementitious material starts to hydrate and generate heat. Question: given a certain grout layer thickness, do all of the specified manufacturers call for the same amount of aggregate extension? Bonus question: once aggregate is added into the mix...does that not transmute grout into concrete?) For the proposed repair at hand...is the repair truly a structural fix? Or is the honeycomb repair merely a shallow cosmetic treatment that really might not need to be tested or inspected? Does the Owner want to pay for such level of attention? As you can see, the topic of construction grout--even for something that seems so simple such as a honeycomb repair--or as important as a load-bearing column base plate condition--can get complicated quickly.  Perhaps these complications are why it has taken the folks who confect concrete building codes so long to address them. rzuellig Thu, 21 Sep 2023 19:17:00 GMT f1397696-738c-4295-afcd-943feb885714:358 https://ascconline.org/Home/News/articleType/ArticleView/articleId/357/Cement-in-Concrete-Decreasing-as-Sustainability-Expectations-Increasing#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=357 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=357&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/357/Cement-in-Concrete-Decreasing-as-Sustainability-Expectations-Increasing Mike Hernandez, Technical Director The Voice Newsletter September 2023 Several years ago, climate change and sustainability were not something the concrete construction community would hear much about. Now action on sustainability is increasing all around us, which translates to less cement in concrete and more supplemental cementitious materials. In the last few years, the following has occurred: The federal government has a National Climate Task Force and the 2022 ~$500 billion dollar “Inflation Reduction Act” allocates billions toward lowering carbon (clinker) in concrete. The United Nations is “empowering the next generation for climate justice” on their website homepage and meeting this 9/18 – 9/19/23 to strength international commitments to their 17 Sustainable Development Goals targeting major progress by 2030. State and local governments like California and Colorado are legislating through programs like the Colorado “Buy Clean Act” to establish maximum acceptable Global Warming Potential (GWP) limits. ACI has introduced NEU, A Center of Excellence for Carbon Neutral Concrete and a Concrete Construction Sustainability and Resilience Assessor certification along with committees 130 Sustainability and 323 Low Carbon Concrete Code. In addition, committees 318 structural code and ACI 301 concrete specification now have sustainability subcommittees.  The Portland Cement Association (PCA) has the Roadmap to Carbon Neutrality which has a goal to be carbon neutral by 2050. A map of all the PCA affiliated cement facilities that have switched to IL and therefore are no longer manufacturing I/II cement can be found here:  https://www.greenercement.com/plcavailability. In 2022 – 2023 the cement industry substantially increased the use of type IL cement from near zero to ~40% of the U.S. market. Limestone Calcined Clay Cement or LC3 which only uses 50% clinker in the cement vs ~95% clinker in Type I/II cement is the next generation of cement in development. It is already in use in India and parts of Africa through a collaboration with the Swiss Global Programme in Climate Change. Additional information here: https://lc3.ch/ NRMCA has a Sustainable Concrete Plant Certification and a Concrete Sustainability Professional Certification. Environmental Product Declarations (EPD’s), which have the environmental impact of specific concrete mixes are being hosted on their website. ASCC initiated a Sustainability Committee, chaired by Bev Garnant and Bruce Suprenant, in June of 2023 and a Type IL cement subcommittee emerged shortly thereafter. ASCC’s “Alert! Portland Limestone Cement” can be downloaded from the member Sustainability section of our website to share with your customers. ASCC is in discussions to provide discounted EPD’s to our members. ASCC Members that are likely interested are members who put up mobile batch plants and are not NRMCA members. All of this to say that ASCC members will be expected to be engaged in sustainably initiatives across the country probably sooner than we realize. ASCC will continue to advocate for research and testing so that concrete contractors are not alone in finding the unexpected outcomes of new blends of concrete. We need your success stories on projects that went well and how you overcame challenges on projects that did not go as expected. Through our collaboration we can navigate a low carbon concrete future. rzuellig Thu, 21 Sep 2023 19:16:00 GMT f1397696-738c-4295-afcd-943feb885714:357 https://ascconline.org/Home/News/articleType/ArticleView/articleId/350/Guidance-for-Concrete-Contractors-20-in-a-series#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=350 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=350&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/350/Guidance-for-Concrete-Contractors-20-in-a-series Jim Klinger, Concrete Construction Specialist The Voice Newsletter August 2023 Question: We are building an addition onto a small commercial steel building.  The vertical supports for the elevated work consist of relatively light structural steel columns that sit on concrete footings, each with footing dimensions 2 ft long by 18 inches wide by 12 inches deep. Our submitted mix design is 3000 psi at 28-day concrete with a 0.45 w/cm ratio. The general contractor (GC) is building the project schedule and has asked us "how long after the footings are placed must we wait before the steel columns can be erected?" We have always assumed 70 percent of the 28-day nominal design compressive strength was the rule of thumb everyone used to trigger steel erection. The strength test backup submitted by our ready-mix supplier indicates there should be no problem hitting that 70 percent threshold (2100 psi) in 7 days. We have not found erection wait time addressed in the construction documents or ACI documents, but this is a city job and we want to make sure. What wait time should we advertise to the GC?. Answer: The erection wait time is going to be determined by several factors, some of which are not in your control. The governing body that actually sets steel erection requirements is OSHA (Occupational Safety and Health Administration). The two OSHA sections that apply are as follows: 1926.752(a) Approval to Begin Steel Erection: "Before authorizing the commencement of steel erection, the controlling contractor shall ensure that the steel erector is provided with the following written notification(s): 1926.752(a)(1) "The concrete in the footings, piers and walls and the mortar in the masonry piers and walls has attained, on the basis of an appropriate ASTM standard test method of field-cured samples, either 75 percent of the intended minimum compressive design strength or sufficient strength to support the loads imposed during steel erection." Suggest reminding the GC at the preconstruction conference to submit a request for information (RFI) to the structural engineer, who needs to specify concrete compressive strength test criteria that the GC and steel erector can follow. Depending on the erection loads, it appears possible that the engineer could specify a compressive strength less than 2250 psi (75 percent of 3000 psi). At that time, the engineer should also specify what ASTM standard tests are acceptable, number of field-cured cylinders, and so on. All these items are outside of your wheelhouse, since they apply to a follow-on trade. For your part, your ready-mix supplier should review the RFI response and confirm when their product should be able to meet the compressive strength requirements specified by the design team. The Owner's inspection agency will also be able at that time to determine what tests, if any, they need to arrange. Once the test results are acceptable, it is the GC's responsibility to follow OSHA and advise the steel erector in writing that steel erection may proceed. Photo credit: CKC Engineers, Seattle (N.B.: If this was a concrete high-rise job, it is totally conceivable that a slab could be placed in the morning, and by late that same afternoon a lift of columns could be placed on that fresh concrete slab as indicated in the photo, above. Also interesting to note here that ACI 318-19 discusses concrete compressive strengths required to trigger application of prestressing forces, which sometimes can be less...much less...than 2500 psi...see ACI 318-19 excerpt, below). _____________________________________________________________________________ Question: We are preparing to place a slab-on-grade (SOG) next week in a large, enclosed warehouse setting where construction equipment appears to be creating an atmosphere heavy with carbon dioxide (CO2). The GC has asked us to provide information regarding potential concerns they have of carbonation of the new slab surface in such an environment. The GC has assured us the ambient atmosphere inside the enclosed warehouse on concrete placement day will meet OSHA regulations. Can you offer any guidance regarding the potential for the CO2 to affect the slab? Answer: Carbonation is the process whereby the surface of a concrete slab can degrade when exposed to certain amounts of CO2 in the air. Since the GC has advised the air quality inside your work area will meet OSHA limits, we need to understand just what that means. According to the OSHA Occupational Chemical Database, the CO2 permissible exposure limits (PEL) are reckoned as a TWA (time-weighted average) of 5,000 parts per million (ppm) per hour, averaged over an 8-hour work day. Since we know what the CO2 content will be, the question then becomes "can that OSHA level of CO2 of 5,000 ppm potentially affect the surface of the concrete?" And the answer is: not likely. According to one industry article, test agencies set the controlled "ambient" air CO2 content for concrete carbonation test purposes starting at between 30,000 ppm to 40,000 ppm, much higher than what will be ambient at your jobsite. In other words, if the humans will be OK, the concrete slab should be plenty fine as well. Note: Normal ambient air CO2 content can run 300 ppm to 400 ppm outdoors all the way up to between 600 ppm to 900 ppm in urban areas. A link to the OSHA Occupational Chemical Database cited above is here. _____________________________________________________________________________ Jim Klinger Joins Baker Construction’s Podcast ASCC member Seth Tandett of Baker Construction hosts a podcast called "concrete logic" aimed at various stakeholders in the concrete construction business...contractors, engineers, architects, suppliers, educators and so on. By the time you read this, the podcast will be approaching its 60th episode. We visited Seth's podcast here a few weeks ago to tape Episode #54 and discuss the "Concrete Contractor's 12 Most Essential Books". To oversimplify enormously, the cost to purchase these publications is less than $600, the smallest investment with the biggest return a concrete contractor or structural engineer can ever make. We explain why during the podcast. Here's the list: ACI 301-20 Specifications for Concrete Construction ACI 117-10 Specification for Tolerances for Concrete Construction and Materials ACI 318-19 Building Code Requirements for Structural Concrete Field Reference Manual ACI MNL-15(20) ACI-ASCC Contractor's Guide to Quality Concrete Construction, 4th ed., MNL-5(19) Tolerances for Cast-in-Place Concrete Buildings: A Guide for Specifiers, Contractors, and Inspectors Guide to the Design and Construction of Concrete Toppings for Buildings User's Guide to ASTM Specification C94/C94M on Ready-Mixed Concrete, 2nd ed., ASTM MNL49-2ND Formwork for Concrete, 8th ed. ACI SP-4(14) ACI 302.1R-15 Guide to Concrete Floor and Slab Construction Significance of Tests and Properties of Concrete & Concrete-Making Materials ASTM STP 169D ACI 117.1R-14 Guide for Tolerance Compatibility in Concrete Construction During the podcast, there is ample discussion describing why ASCC members (and other stakeholders) should have each and every one of these publications on their desktops. We stopped at 12 publications due to time constraints. Of course, there are other high-value documents that belong on your library shelf, but these 12 are a fantastic start. Here's a link to Seth Tandett's podcast "concrete logic", episode #54. Check it out. rzuellig Thu, 31 Aug 2023 13:31:00 GMT f1397696-738c-4295-afcd-943feb885714:350 https://ascconline.org/Home/News/articleType/ArticleView/articleId/344/How-Can-Technology-Change-the-Way-You-Work#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=344 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=344&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/344/How-Can-Technology-Change-the-Way-You-Work Mike Hernandez, Technical Director The Voice Newsletter August 2023 There are various new and developing technologies on the market that are of use to concrete contractors. ASCC technical staff and Associate Members can assist you with many of them. Members can also ask for feedback from the general membership in the ASCC Forum. Total Station The most accessible technology may be to invest in a Total Station for self-performed layout or verification of layout by others. They vary in cost from $3,500 to over $40,000 for a robotic machine capable of long-distance land survey. There are 5 arc seconds, 3 seconds and 1 second instruments on the market. If you are constructing a medium-size commercial building or smaller, a 5 second Total Station is probably just fine. Personally, I prefer the 2-man team with an instrument man and a rod man. They often act as a journeyman and apprentice team. The rod man is staking points and can someday be an instrument man himself. Also, a robotic Total Station was stolen in a grab and run operation too close to a busy Miami street years ago. Fortunately, the surveyor had written his name and our company name under the batteries with ultraviolet ink, so he was able to identify it at a pawn shop several weeks later with a UV flashlight, despite the serial numbers being scratched off. You will also need software, a data collector and training. I feel the expense is well worth the upgrade in quality vs traditional processes. Laser Scanner In the upcoming September issue of ACI’s Concrete International, there is an article by ASCC Member Leo Zhang with The Conco Companies regarding laser scanners. The article compares the performance of several competing scanners and provides guidance on their speed and accuracy at various distances. Absent from the article is the cost. The ones tested range in price from $23,000 to $104,000 plus the cost of the software and training. Scanners are helpful in capturing existing conditions or performing as-builts. Having used scanners on projects for 17+ years and as a member of ACI 117 laser scanning subcommittee, they are a double-edged sword. They will find mistakes you did not realize were there which could be used against you or help you mitigate a dispute with minimal grinding, patching, and rescanning. Our team performed multiple rounds of grinding-patching-scanning of vertical shear walls to minimize the impact of a stucco sub wanting $100,000 to thicken the coatings on several 5-story shear walls back in 2007 with similar mitigation processes more recently. Flatwork slab topographs or “heat maps” are the most common work products. It will find the high, intermediate, and low points in a slab. Be careful that the contour line spacing is reasonable if someone else performs the scans. Scans of elevated decks prior to--then after--shoring removal have made several disputes go away over the years because concrete contractors can’t control deflection, only the top surface (prior to shoring removal) is in their control. Building Information Modeling (BIM) If you are constructing a moderately complex structure or if the drawings seem incomplete, then consider using BIM to model the concrete frame for the project. The structure is constructed digitally before going to the field. The Mechanical-Electrical-Fire Protection-Plumbing trades are modeling their work regularly to cram their scopes into walls and ceilings using clash detection and coordination so this might be happening with the general contractor already. Some aspects of the final concrete are often not coordinated properly in the "For Construction" set of plans or additional information is added during shop drawing review. The goal of the BIM modeling is to provide the field with a coordinated set of line drawings checked against architectural drawings, structural drawings, civils and includes block outs and embeds. The BIM coordinated concrete shop drawings become the single source of truth. This exercise should decrease risk, improve efficiency, and thus reduce cost. From this you can provide model-based layout to a total station, run schedule simulations (4D) or even use it to model the formwork and rebar. BIM can even be used with a virtual reality headset to digitally walk through the structure. The investment is substantial, so consider using a domestic or international 3rd party consultant until you are familiar with the processes enough to know which software to buy and have an enthusiastic modeler on staff. Part of the issue with evaluating your return on investment is it will be impossible to accurately quantify actual savings of a well-coordinated set of drawings vs finding issues during concrete construction operations or worse, by a follow-on trade. I like to say, “It is hard to place a value on the bus you did not get hit by.” When a project goes smoothly, and the team meets the schedule and quality goals then moves to another project without rework, that is a good project! Drones The use case for drones is for progress photos and capturing post tensioning and rebar prior to concrete placement. As an FAA Licensed part 107 drone pilot, I have flown dozens of flights to capture progress photos. Having those progress photos was helpful in updating the master schedule and billing percent complete. Other projects have used a drone flying a programmed route like mowing a lawn to capture rebar, post tensioning and conduits prior to placing concrete. The series of images can be combined for a high resolution as-built composite image if a slab ever needs to be drilled. If you are going to use a drone on a commercial jobsite, go through the proper licensing and liability insurance procedures. Artificial Intelligence (AI) There are several AI tools available if you want to push the innovation envelope. One is a scheduling tool, which will run thousands of schedule “what if” scenarios based upon the sequence logic, durations, manpower and equipment constraints you input. It will generate the fastest solution to complete the project. The more complex the schedule, say 2500+ activities, the more likely it is to come up with a novel solution. A former employer was using this tool 6 years ago, and we tested our plan against it. Having managed projects with a best-case scenario master schedule it is a high-risk and high-reward setting. A few hiccups in manpower or formwork cycling and the ultra-fast plan is out the window with craft labor and general conditions consuming the perceived savings. Massive overtime and a difficult conversation with your client come next. The lesson learned was to under commit and over deliver as much as possible. Try this tool when the whole project team can get on board with your innovative AI plan to share the risk. If you would like additional details about AI leveraged project scheduling, please contact me. A less risky use of AI is for language translation. With a predominantly Hispanic workforce in many companies, the more we can provide our workforce content in their native language, the more likely we are for them to internalize the text. AI can translate to hundreds of languages. I am still trying to determine if Google Translate or Chat GPT does a better job with concrete construction lingo. Your feedback is welcomed.    As contractors, we must make buy-sell-lease decisions for the benefit of the long-term health of the organization. Fellow ASCC members and staff can help you recognize the pros and cons of technology investments. Take advantage of these resources as a benefit of ASCC membership. rzuellig Thu, 31 Aug 2023 13:13:00 GMT f1397696-738c-4295-afcd-943feb885714:344 https://ascconline.org/Home/News/articleType/ArticleView/articleId/340/ALERT-Bulletins#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=340 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=340&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/340/ALERT-Bulletins July 10, 2023 – The American Society of Concrete Contractors (ASCC), St. Louis, has published its first ALERT!, a new bulletin to apprise members of issues and developments in the concrete construction industry. The first ALERT! covers Portland-Limestone Cement Concrete. “ALERT! bulletins will be published as needed to provide timely notice of unusual, challenging, and sometimes complex circumstances affecting the industry,” said Bruce Suprenant, PhD, PE, FACI, ASCC Sustainability Committee co-chair. rzuellig Mon, 10 Jul 2023 16:37:00 GMT f1397696-738c-4295-afcd-943feb885714:340 https://ascconline.org/Home/News/articleType/ArticleView/articleId/335/Sustainability-Committee#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=335 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=335&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/335/Sustainability-Committee May 22, 2023 – The American Society of Concrete Contractors (ASCC) announced that Bruce Suprenant, P.E., PhD., FACI, and Bev Garnant, HACI, have been retained to develop and manage the association’s sustainability initiative. Suprenant and Garnant are ASCC’s former technical director and executive director respectively. rzuellig Mon, 22 May 2023 17:45:00 GMT f1397696-738c-4295-afcd-943feb885714:335 https://ascconline.org/Home/News/articleType/ArticleView/articleId/337/Guidance-for-Concrete-Contractors-17-in-a-Series#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=337 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=337&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/337/Guidance-for-Concrete-Contractors-17-in-a-Series Jim Klinger, Concrete Construction Specialist The Voice Newsletter May 2023 Question:  We are building a post-tensioned (PT) concrete parking garage that features 3 levels below grade and 4 levels above street level. We bid the job to a General Contractor (GC) who in turn is working for a private developer. At bid time, the requirements for the quality of formwork and allowable deviations for formed concrete surfaces were stated in project specification section 03 11 00-1.04-B as follows: 1.04 Quality Control A. General: Conform with ACI 301 except as modified by the requirements specified herein and the details on the Drawings. B. Allowable Tolerance: Design, construct, set, and maintain the formwork so as to insure completed work within the suggested tolerance limits specified in ACI 347, Section 3.3.1. C. See Section 03 35 00 for required traffic surface tolerances of slabs. The "ACI 347" referenced above by the design team is ACI 347-04 Guide to Formwork for Concrete, which contains Table 3.1- Permitted abrupt or gradual irregularities in formed surfaces as measured within a 5 ft (1.5 m) length with a straightedge. The class of surface indicated in Table 3.1 is consistent with current ACI 117-10, section 4.8.3 Formed surface irregularities (gradual or abrupt). Prior to construction, we hired a professional formwork engineer to prepare formwork shop drawings that showed the shoring and reshoring sequences, concrete outlines, construction joints, large openings, and curbs. Cut sheets for the formwork materials (e.g. scaffold frames, aluminum beams, plywood, wall ties, form release) were submitted under separate cover. Our submittal was approved with only slight adjustments made to CJ locations by the engineer. Formwork tolerances and form quality were not addressed on the shop drawings. The project preconstruction conference format (meetings traditionally held onsite in the construction trailer) was changed to a virtual meeting thanks to COVID. Much of that meeting was spent talking about COVID protocols and concrete ready-mix truck haul routes.  The topics of formwork quality and formed surface features never came up. The project is now complete, and we are having difficulties getting our retention payment. The GC (and Owner) are saying some of the columns we built do not meet the construction document requirements and need to be ground and patched. The photo of one of the garage columns indicates an abrupt surface irregularity (offset between adjacent pieces of column side formwork facing material) of one-half inch, maximum. Our position is that the as-built column depicted in the photograph meets all construction document quality requirements and that our retention should be released immediately. During the course of construction, no NCRs (noncompliance reports) were issued, and we are surprised to see this being raised now. Is the GC justified in holding our retention money? Answer: In a word...no. That is if the measured offset is indeed a half-inch or less anyway. Here's the story on this column and why it is plenty fine--contractually speaking--just the way you built it. In theory, the design team is supposed to research and understand reinforced concrete, concrete tolerances, and the interface among concrete and all follow-on trades before confecting a fully coordinated set of construction documents. In a perfect world, said design team would have a working knowledge of ACI 117.1R-14: Guide for Tolerance Compatibility in Concrete Construction, which lays out the responsibilities of the various project stakeholders and suggests helpful strategies that can be used to keep tolerance conflicts and potential back charges at bay. In this case, the design team did not have a grip on the basics of concrete formwork tolerances right from the get-go, let alone trying to coordinate the work with any follow-on trades. The problem started when the designers wrote specification section 1.04-B, above. Instead of doing the work and understanding the project, they punted and essentially said "just do whatever ACI says". The ACI class of formwork quality was never called out. Things got worse when the preconstruction meeting got derailed by COVID. Now it appears the Owner and GC are saying you somehow owe at least ACI Class B quality formed surfaces to the project.  There seems to be a fundamental misunderstanding of what ACI Class "B" is. Any competent designer knows that before putting pen to paper, the "Mandatory Requirements Checklist" in ACI 117-10 must be navigated. This is not an option, it is mandatory. The designer owes it to the Owner to complete the checklist before issuing the construction documents to bidders. In this case, had the designer read checklist section 4.8.3, it would be evident that ACI Class “B” is for "coarse-textured, concrete-formed surfaces intended to receive plaster, stucco, or wainscoting.” In other words, concrete covered later by the work of a follow-on trade. If the designer looked to see what Class "C" work is, it would become painfully obvious that Class “C” is the "general standard for permanently exposed surfaces where other finishes are not specified.” And this is exactly what you did. Since no other finishes are specified, Class “C” automatically kicks in by default. The half-inch offsets are OK. No uncompensated grinding or extra patching is required. You met your contract quality requirement and need to collect your retention.  (N.B.: I call Class "B" the "Blind Man's Tolerance.” There is nothing at all that is visual when you are dealing with Class B work. It's all about coarse textures and offsets and bugholes that can all be totally evaluated by touch. Class “B” has nothing at all to do with exposed concrete in a garage or anywhere else. You would be amazed at how many designers have not bothered to read, understand, and follow the ACI 117-10 Mandatory Requirements Checklist). rzuellig Mon, 15 May 2023 16:05:00 GMT f1397696-738c-4295-afcd-943feb885714:337 https://ascconline.org/Home/News/articleType/ArticleView/articleId/336/Great-Committee-Week#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=336 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=336&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/336/Great-Committee-Week Mike Hernandez, Technical Director The Voice Newsletter May 2023 ASCC had a great Committee Week May 1st – 3rd in St. Louis both technically and socially. The Manufacturers Advisory Council discussed several issues including the need to bring new talent into the construction industry. We have an aging workforce and are losing people to retirement. Members encouraged one another to provide career opportunity paths and hire less experienced employees to try to grow their next generation of leaders.    ASCC’s two recent webinars help address the same craft labor challenge. April webinar “From Curiosity to Career: Build Their Future in Construction” presented the website byf.org which is set up to being people into construction by describing different trades, the needed skills, their wages and a Career Card. For example, a Concrete Finisher “build foundations, floors, walls, roads and other structures that are made using concrete.” Needs to be active, detail oriented and team player. Average annual salary $58,046. A spinoff, Career Starter, was presented in the May webinar “Build Your Talent Pipeline with Career Starter.” It helps connect job seekers with educators and potential employers is found on their website. Both are affiliated with the training organization NCCER. This is an excellent resource to connect you with local talent. For the Technical Committee, multiple documents were distributed prior to the session including three new Position Statements: two for polished concrete and one on Considerations for Deferred Submittals. ACI Committee progress was discussed by various attendees. A lively discussion of ASTM C595/type 1L cement concrete ensued. Some contractors stated they have had great success with Portland-limestone cement (PLC). Others have stated even within the same metro area type 1L mixes will respond differently to changes in course aggregate and sand. ASCC is committed to a deeper dive into PLC/type 1L this summer through the Sustainability Committee headed by Bev Garnant and Bruce Suprenant.  I explained the CTAC program which seeks to ensure concrete field tests and initial curing are done correctly by using ACI Certified observers, QC personnel from the contractor or a ready mixed producer. According to data collected by CTAC, initial curing is performed incorrectly 40%-60% of the time in various states. More information is at concretetac.com. The Paving Committee had an extended conversation about the Paving Tool Kit sponsored by NRMCA. This package will help concrete contractors convert asphalt paving into concrete with NRMCA design assistance for thickness and additional details. Brian Killingworth encouraged members to submit good paving photos or drone video to him for possible social media posting by NRMCA. Thank you to Ray Merlo for his term as Chair.  Emerging Leaders Committee had a fascinating discussion about the use of Chat GPT Artificial Intelligence (AI), software to generate social media posting content and translate documents from English to Spanish, even to a specific dialect. Knowledge of Chat GPT was split across age demographics with under 35’s already using it and over 50’s like me completely unaware of AI’s potential to assist us. This could be a tool to help ASCC with initial translations then asking members to confirm instead of creating Spanish translations of Position Statements or other documents. Safety & Risk Management Council had a national presenter who discussed the legal precedents being established, risks and potential need for accommodation associated with medical cannabis.  Evaluating “fit for duty” has new technical options available through phone apps.   Decorative Concrete Council started with a good safety moment in which Diedre Dann spoke about a suicide prevention and mental health program. Ray Hefner provided an update on the upcoming Annual Conference. Additional discussion about the need for Spanish translation of documents and the potential for AI to assist in the project. There was a report on a successful Community Project at Leeds High School, managed by Brandon Meeks. The idea to use ASCC Decorative Awards submissions as potential social media posting content was well received.  Keep in mind that Committee Meetings are generally open to any member. Only a few are closed meetings. So, feel free to attend as many committee meetings as you can while at an ASCC gathering. This is your association, the more effort you invest, the greater the reward in personal connections and professional advice. rzuellig Mon, 15 May 2023 15:54:00 GMT f1397696-738c-4295-afcd-943feb885714:336 https://ascconline.org/Home/News/articleType/ArticleView/articleId/333/Guidance-for-Concrete-Contractors-16-in-a-Series#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=333 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=333&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/333/Guidance-for-Concrete-Contractors-16-in-a-Series Jim Klinger, Concrete Construction Specialist The Voice Newsletter April 2023 Full Disclosure: Every once in a while, we field ASCC Hotline calls that appear straightforward at first but quickly elevate into interesting exercises in onion-peeling. In this case, it takes a little bit of wordsmithing to arrive at truth's upper floor and save our ASCC Hotline callers from making a mistake or taking a bath on a business deal. ____________________________________________________________________________  Question: We have just signed the subcontract for our first high-rise project, 30 stories from street level to roof. The typical floor footprint is a rectangular area comprising roughly 25,000 square feet. The elevator and stair shafts are centrally located in one core. We bid the job assuming the use of a climbing formwork system to build the elevator/stair core walls. Our schedule shows us placing the core walls with the proprietary system three floors ahead of the slabs in a 5-day cycle. (Even though the core will be 3 floors ahead, wall placements will be pumped one lift at a time). Our outside formwork designer has asked us what tolerances he should assume for the design. The contract specifications vaguely tell us to "conform to tolerances per ACI 117.” We believe the tolerances we need to follow are found in ACI 117-10, Section 4--Cast-In-Place Concrete For Buildings. The formwork designer is telling us since we are using a climbing form system, he believes the tolerances that apply to our core wall scope are found in ACI 117-10, Section 7--Cast-In-Place, Vertically Slipformed Building Elements. Sure enough, when we turn to Section 7, the very first call-out we see is Section 7.1--"Deviation from plumb for buildings and cores.” Since we are obviously building a building and core, is our formwork designer's position correct? Does our climbing form constitute a slipform? Answer: In a word, no. But we see what you mean. There are two hangups. One is the ACI CT-20 definition of "slipform", which is defined as "a form that is pulled or raised as concrete is placed.” This implies the concrete placement is performed in a continuous extrusion instead of the stop-start process you will have when you pour the walls one story-height lift at a time as scheduled. The second hangup can be found in ACI SP-4(14) Formwork for Concrete-8th Edition, Chapter 18: Special Techniques in Concrete Construction, which addresses the various means and methods available for slipforming concrete. SP-4 acknowledges there may be some confusion regarding tolerances as follows: "ACI 117 does not differentiate between slipformed building cores and other slipformed building elements. However, it would be desirable for the designer and builder to review tolerances and verify the specified values are appropriate for the intended use of the structure. This will facilitate achieving the best speed and economy consistent with needed precision. Slipformed cores and shafts of buildings that tie into other adjacent parts of the building should meet the same tolerances for plumbness as those for building walls.” Here's a suggested course of action for you and your formwork designer. ACI Committee 117 has published a little-known document called ACI 117.1R-14: Guide for Tolerance Compatibility in Concrete Construction. This comprehensive guide document compares the concrete tolerances specified in ACI 117-10 with tolerances used by most of the follow-on building trades, including elevators, stairs, doors, windows, curtain wall, precast concrete, CMU, stone panels, tile flooring, wood flooring and so on. There is also guidance given regarding the compatibility of ACI 117 concrete tolerances with requirements specified in (and mandated by) the Americans With Disabilities Act and Architectural Barriers Act Accessibility Guidelines (ADA/AB-AG). Have your formwork designer review ACI 117.1R Section 5.2--Elevator cores and hoistways, including Table 5.2.1.1, which compares tolerances followed by the National Elevator Industry, Inc. (NEII-1) and tolerances specified in ACI 117-10, including slipformed core walls. Any questions should then be followed up via RFI (preferred), questions asked on the formwork drawing submittal (semi-acceptable) or items to table at a preconstruction meeting. (N.B.: Preconstruction tolerance meetings among contractors are mandatory (ACI 117-10, Section 1.1.3). The owner and/or design team cannot be forced to attend. Preconstruction tolerance compatibility meetings to discuss elevator embeds, shaft sizes, pit and sump sizes, and slipforming (if actually used) are similarly suggested in ACI 117.1R-14, Section 5.2.3--Construction Strategies. Suggested attendees include the concrete contractor, construction manager, elevator manufacturer, and elevator installer. Once again, the owner and/or design team cannot be required to attend. ACI 301-20, Section 1.6--Preconstruction conference is the one ACI document that actually does specify mandatory attendance by the Architect/Engineer, owner, or owner's representative but only if the meeting itself is specified. No matter which way you slice it, ASCC contractors should make every effort to seize the opportunity to collaborate with the design team and discuss not only tolerances, but the project in general. For more information on tolerance compatibility, have a look at ASCC Position Statement #6: Division 3 versus Division 9 Floor Flatness Tolerances and ASCC Position Statement #18: Concrete Tolerance Coordination. _____________________________________________________________________________ Question: We placed a slab on grade about a year ago at a condominium project. Thanks to the information contained in ASCC Position Statement #7 "Birdbaths on Concrete Slabs,” we were able to educate the Owner about the birdbath phenomenon. Now the Owner is saying the tenants are complaining the birdbaths are not evaporating fast enough and are headed back to meet with Judge Wapner. We cannot find anything in ACI 302 that addresses birdbath evaporation. Are there any industry guidelines that can help get us out of hot water with this Owner? Answer: Don't throw the towel in yet. The industry words of encouragement, the ASCC Technical Division can offer come to us from the National Association of Home Builders (NAHB) "Residential Construction Performance Guidelines Consumer Reference, Fifth Edition.” In this document, standing water is covered in Section 12-4-2 Driveways and Sidewalks as follows: "Standing water greater than 3/8 inch in depth should not remain on the surface 24 hours after a rain.” In Section 12-2-2 Concrete Stoops and Steps, the NAHB verdict is "minor amounts of water can be expected to remain on stoops and steps for up to 24 hours after rain.” So, let us call it a day. This witness may step down, your honor. ______________________________________________________________________________ Profound thanks from the ASCC Technical Division are hereby extended to ASCC member Oscar Antommattei (Kiewit) for both organizing and hosting the special Technical Symposium held at the ACI Spring Convention last week in San Francisco honoring our very own Dr. Bruce Suprenant. This all-day session featured 21 speakers paying tribute to Bruce in their own way for generously using his technical expertise to educate us all and save us piles of cash and prestige in the process. ACI has somehow recorded the presentations, and the VOICE will let you know when the session tapes become available on the ACI web page. ______________________________________________________________________________ Congratulations are hereby extended to ASCC member Lingfeng "Leo" Zhang (Conco) for his recent appointment as chairman of ACI/ASCC Joint Subcommittee 117-L: Laser Scanning. Leo participated in the ASCC laser scanning study described in the Jan. 2019 and Feb. 2020 editions of ACI's Concrete International Magazine (CI), and then followed up as lead author and field investigator with colleagues Suprenant and Klinger in three laser scanning articles published in CI in 2022: "F-numbers and Textured Concrete Surface Finishes" (May 2022), "Slab-on-Ground Thickness Measurement" (July 2022) and "Presenting Laser Scan Results for Slabs-on-Ground" (September 2022). Way to go, Leo! rzuellig Sat, 15 Apr 2023 19:20:00 GMT f1397696-738c-4295-afcd-943feb885714:333 https://ascconline.org/Home/News/articleType/ArticleView/articleId/330/Guidance-for-Concrete-Contractors-15-in-a-Series#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=330 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=330&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/330/Guidance-for-Concrete-Contractors-15-in-a-Series Jim Klinger, Concrete Construction Specialist The Voice Newsletter March 2023 Full Disclosure: To recap our column that appeared in last month's ASCC VOICE newsletter (Feb. 2023, "Guidance for Concrete Contractors, #14 in a Series"): we introduced and explained issues related to the performance of the "new" ASTM C595 Type 1L portland-limestone cement, hereinafter referred to as "PLC". Our reporting was sourced via jobsite accounts disclosed by concrete contractor members during ASCC Hotline phone calls, information presented in industry trade publications, and two educational seminars we attended at the 2023 World of Concrete designed to focus specifically on PLC industry impact. To gain a better understanding of how the new PLC is affecting ASCC members, we sent a survey to our contractor members in December 2022. Responses continue to come across the transom; in other words, the survey is still very much a work in progress. What follows is a status report that presents what we have learned. [N.B.: It is important to note there are several actual project case studies that were in the process of being reported to the ASCC Technical Division that were cut short by nondisclosure agreements (NDAs). Unfortunately, such gag orders are a recurring and quite damaging legal tool we described in our Feb. 2021 VOICE article regarding the so-called "Spearin Doctrine." It is a shame technical data, including mix designs, strength test reports, mill certs, and petrographic analyses that might help reveal the root causes of costly PLC failures must now remain under seal. Those examples, perhaps the most valuable of all are not included in the ASCC PLC survey (per se).] ______________________________________________________________________________ The ASCC PLC survey titled " ASCC Survey on Contractor Experience with Type 1L Cement" consisted of 17 questions asking members to report their experiences with Type 1L PLC. To date, we have received thirty-six responses. The respondents are structural concrete contractors located throughout the United States. Although company sizes varied--22 contractors reported annual sales volume more than $50M. The survey focused on three main potential PLC problem areas: compressive strength, fresh concrete set times, and water demand. Respondents were also given the opportunity to describe other issues, including potential problems with finishability, shrinkage cracks, effects of cold weather and so on. No respondents indicated PLC issues related to decorative or polished concrete. (Although not asked, no respondents indicated issues with PLC durability or problems related to PLC shotcrete applications). Note, that although there were 36 responses to the survey, not all respondents answered all questions. ______________________________________________________________________________ Question: We are seeing advertisements by one concrete management software developer who states, "Type 1L cement is more temperamental, requiring ready mix producers to have tighter control over the amount of water added to the concrete and the number and speed of drum revolutions in transit. Because it is sometimes ground finer, there can be an increase to the concrete's water demand as well as a decrease in strength and set times. A greater degree of control is required in order to sustain the desired performance of concrete containing 1L cement...achieving consistency across loads is particularly vexing with 1L cement, as minor changes in material properties, such as aggregate moistures, can have significantly more impact.” The solution, they then say is to install sensors inside the ready mix trucks and monitor concrete properties while the truck is on the way to the jobsite. Has this adjustment technique been used on any ASCC contractor members' projects? Answer: This is a new one on us as are several of the PLC side effects reported from our members. In another industry advertisement, we found the following statement explains how to offset potential strength reduction caused by limestone use: "A more effective approach is to use a strength-enhancing cement additive, which can have a significant impact on strength. For a typical 5MPa (725 psi) gain, it would be possible to increase the limestone by 7% for the same mill output. Given that strength is substantially reduced in higher limestone levels (>5%), the selection of the appropriate quality-improving additive is important." Such examples indicate there is more going on with PLC behind the scenes than we are being led to believe in current industry promotional media. In Europe, for example, where "PLC has been used for more than 25 years," one major admixture producer addresses the issue of unintended consequences head-on : "The behavior of fresh concrete--expressed as slump flow or workability--is also a key factor, especially in terms of workability-enhancing concrete admixture costs. High limestone content and increased fineness lead (unavoidably) to higher water demand which generally increases the amount of superplasticizer needed to achieve targeted workability. Cement producers would like to avoid such discussions when introducing new and more environmentally-friendly cements to the concrete market." These examples all relate to cement and concrete property issues that come into play before the final PLC product reaches the end user--the concrete contractor--at the jobsite. ______________________________________________________________________________ Question: In addition to ASCC, where can concrete contractors go to find unbiased information about PLC? Almost all of what we find are industry promotional advertisements that state PLC is a "plug and play, 1-to-1 powder swap" proposition with zero side effects. Answer: Despite the NDAs described above, side effects related to PLC continue to appear on concrete construction projects nationwide. The ASCC PLC survey is no doubt just a partial slice of what is happening. We must acknowledge not all concrete contractors or suppliers are members of ASCC, ACI, NRMCA, PCA and so on, where such information telling both sides of the story would likely be found. ASCC has recently established a Sustainability Committee, where PLC will be one of the hot topics. We are also working collaboratively with the Portland Cement Association (PCA) and the National Ready Mixed Concrete Association (NRMCA) to assist contractors in understanding and managing all aspects of the construction industry efforts to reduce embodied carbon in the environment. One committee member, Dr. Heather Brown, PhD., has suggested a forum with admixture and cement suppliers is necessary to discuss compatibility, cement chemistry and further testing that will be required to address and solve the PLC issues. Dr. Brown has worked with ASCC on previous projects, and currently is the VP of Quality Control at Irving Materials, overseeing 180 concrete plants. One of the seminars we attended at the World of Concrete 2023 was presented by Tim Cost, P.E., titled "What You Need to Know About the New Type 1L Portland-Limestone Cement." This common-sense, straightforward presentation described the PLC scenario from the grinding process at the mills to potential performance issues encountered in the field. Engineer Cost is the president of V.T. Cost Consulting, LLC and is an expert with over forty-one years of experience with cementitious materials, including twenty-one years at Holcim. Tim will be one of our featured speakers at this year's ASCC Concrete Executive Leadership Forum (CELF), covering PLC issues and how concrete contractors like us can successfully adjust to PLC use and what to look for in PLC mill certs and mix designs. For printed material, we found one interesting article published by the Construction Specifications Institute (CSI) titled "Concrete's 'Cobra' Effect: The unintended consequences of 'simple solutions' in reducing embodied carbon in concrete.” This article appeared in the "Construction Specifier" magazine in January 2023, and describes many of the unsavory PLC side effects that ASCC members have reported. A link to the CSI article is https://www.constructionspecifier.com/concretes-cobra-effect-unintended-results-of-embodied-carbon-reduction/. There are industry advertisements aimed at specifiers that suggest all that is needed to make things right is for a specifier to merely open up their Division 3 specification template files and change "ASTM C150" to "ASTM C595" and then send the specification out for bid and then on to construction. It is hoped that LDPs and concrete specifiers read the CSI "Cobra" article and understand its implications. rzuellig Wed, 15 Mar 2023 14:08:00 GMT f1397696-738c-4295-afcd-943feb885714:330 https://ascconline.org/Home/News/articleType/ArticleView/articleId/329/Happy-to-Be-on-the-ASCC-Team#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=329 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=329&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/329/Happy-to-Be-on-the-ASCC-Team Mike Hernandez, technical director The Voice Newsletter March 2023 ASCC has been an organization that I have admired for years. I am thrilled to be the new ASCC Technical Director. I have been blessed to work with a lot of great teams on projects in the last 25+ years from a few thousand sf of commercial building additions to bridges, airport terminals, high rises and an NFL stadium. A successful project always needs multiple layers of support from the owners, designers and inspectors to the wider construction team down to the individual operators, carpenters and finishers forming and placing concrete. The tradespeople are the true heroes in our industry, and we at ASCC are one more layer of help for the concrete contractor and the men and women of their workforce. I am excited to be part of it. It was great to say hello to many of you at the World of Concrete committee meetings and in the ASCC booths. Looking forward to the opportunity to get to know a broader group of the membership at ASCC events or ACI Conventions under less stressful circumstances than Hotline emergencies. We have many projects in progress including certification, sustainability and improvements to the ACI documents to make them more contractor friendly. Please reach out to me to provide your feedback on what the Technical staff does that adds value to your company and what we could possibly do differently or more of to enhance your ASCC interaction. Don’t panic, Bruce Suprenant will help mentor and transition me part-time through much of 2023 until he can start enjoying retirement. If you have the opportunity to attend, there will be a four two-hour session tributes to Bruce on Tuesday 4/4/23 at the ACI Convention in San Francisco at the Hilton Union Square. Bruce and Ward Malisch before him have left some big shoes to fill, please give me a little grace during this season of change. rzuellig Wed, 15 Mar 2023 14:05:00 GMT f1397696-738c-4295-afcd-943feb885714:329 https://ascconline.org/Home/News/articleType/ArticleView/articleId/325/Guidance-for-Concrete-Contractors-14-in-a-Series#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=325 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=325&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/325/Guidance-for-Concrete-Contractors-14-in-a-Series Jim Klinger, The Voice Newsletter February 2023 Full Disclosure: Over the past year, the ASCC Technical Division fielded several Hotline calls from members experiencing difficulties related to ASTM C 595 portland-limestone cement Type1L, hereinafter referred to as "PLC" (as opposed to "OPC", ordinary portland cements, brand X,ASTM C 150 Types I and I/II and so on). At first glance, it seemed suspect PLC issues might be regional; initial Hotline calls were originating mostly from ASCC members in the southeastern US markets. But once we started investigating, PLC was suspected to be problematic under certain climatic jobsite conditions (e.g. temperatures near 40 degrees F and lower) as well. By the time we met for our ASCC Annual Conference committee meetings in Cleveland (then later, informally, at the ACI Convention in Dallas), it became clear that PLC cement issues reported by our members were neither geographically isolated nor random in nature. In early December 2022, the ASCC Technical Division emailed a survey to ASCC contractor members asking them to describe their experiences, if any, with the "new" Type 1 PLC. Survey results are still being collected and reviewed. But others in the concrete construction industry (e.g. trade magazines and social media) have noticed and discussed potential problems with PLC as well. Just last month, ASCC attended two educational seminars at the World of Concrete; both highlighted the same types of PLC-related issues reported by our Hotline callers. What follows is a confected summary of what we know to date about PLC. As you will see, information that should be disseminated to help all concrete contractors and project stakeholders is hard to come by. "Lessons learned" and project-specific accounts are few; in some cases, attorneys and non-disclosure agreements (NDAs) prevent us from legally gaining access to test reports and other valuable technical data. In other words, names and places used below have been changed to protect the innocent. _____________________________________________________________________________ Early last summer, the ASCC Technical Division took a Hotline call from a member who reported serious problems with the concrete on a major big-box project. The first sign of trouble had actually gone unnoticed up and down the project food chain. The contractor had submitted concrete mix designs with OPC proportions similar to those proven successful over many years using the same ready mix supplier. These were triaged by the Owner's test agency and approved by the LDP. The mandatory preconstruction meeting was held on site, and the first slab placement date was set for two weeks out and put on the books. One week later, the concrete contractor received an unexpected "Dear Valued Customer" letter. The letter stated the ready mix supplier had to resubmit the mix designs "to incorporate an industry-wide change in cement from ASTM C150 Type I/II to ASTM C595 Type 1L." "Please excuse the inconvenience," the letter stated. "This is not a change we requested...this change is being done as a green initiative by the cement industry to reduce the carbon output of cement production...our cement producers have conducted testing and found no significant change in quality or set time." During follow-up clarification phone calls with the ready mix supplier, the ASCC contractor was assured that this in fact would be a no-cost change, that the cement powder was being swapped purely "on a one-to-one basis"... that comprehensive industry testing had already been done...and that similar cement has been used successfully in Europe for 25 years or even longer. "It is a matter of plug and play," they were told. There would be no finishing or strength or durability issues. The ready mix supplier added "we are being told by our suppliers that Type 1L PLC is hereto stay and project stakeholders must learn to adapt." Armed with that reassurance, the new Type1L PLC mix designs were packaged by our contractor member for resubmittal with the explanations..."emergency resubmittal...sorry for the inconvenience...supply chain and climate change issues...please expedite review to help us maintain the project schedule." The design team approved the new PLC mixes and collected their green points. Problems started when the first routine 25,000 SF slab placement that historically would take say a 10-man crew in an 8-hr shift now required 12 to 14 finishers working well into the night on overtime. The problem? The concrete set too slow, and when it finally did set, it went off all at once. The finishers did what they could to try to save the surface, but still had to show up again early the following morning to rework a section of the slab. Subsequent placements required addition of accelerating admixtures. Admixture dosages were adjusted over several deck placements before the contractor felt comfortable tapering the finishing crew back to the size anticipated at bid time. Then the cost reports hit the concrete contractor's PM's inbox, red-flagged with unfunded line items for overtime, rework and accelerating admixture costs associated with the changes. The Owner, who did not initiate the change from OPC to PLC was not thrilled with the worked slab and didn't want to hear any part of delays or extra cost issues or infighting associated with the PLC. As of today, this ASCC member has revealed the decks have been cored and petrographic testing has been undertaken, but the project is now under an NDA gag order. Test results, strength data and other crucial information is now under seal and--for now--the concrete contractor is left holding the bag. ______________________________________________________________________________ Another ASCC Hotline caller described a similar scenario that featured a mix design change from OPC to PLC after the initial OPC mixes were approved. Wall and column footings were placed using the new PLC mix. Two weeks later, a second PLC mix was used in slab-on-grade replacements. Strength tests at 7 days were normal for the footing mix, but at 28 days, the tests ran about 1000 psi low. Same thing for the SOG tests, roughly 1000 psi low at 28 days. Before anyone realized it, all project concrete had been placed and all 28-day breaks were low. The LDP directed cores be taken and tested for strength and petrographic analysis. It was apparent PLC concrete was gaining strength up until 21 days, then gaining almost zero strength after that. The PLC was just flat dying on the vine and upsetting the project Owner. We asked our member to send us the mix designs and test reports, including the results of coring and petrographic analysis when available. At this point, the ready mix producer had embarked on a similar companion test regimen with coring and petrographic analysis. In a follow-up phone call with the contractor, it was revealed this project, too, was now under an NDA. In other words, strength test data and the petrographic analyses performed by the Owner's test agency and the companion testing done by the ready mix supplier are now under seal. The contractor, the GC and the ready mix supplier have all hired their own consultants, prompted by Owner posturing for total removal and replacement of the concrete. The ready mix supplier is saying the Owner's test agency mishandled the cylinders. Once again--we will most likely never know the true cause of the low strength and who will be financially responsible. ______________________________________________________________________________ Question: What exactly is ASTM C 595 Type 1 PLC? Is limestone considered to be a supplementary cementitious material (SCM) with pozzolanic or hydraulic properties such as flyash or slag? Answer: ASTM C 150 currently allows up to 5 percent limestone to be blended with OPC. With PLC, ASTM C 595 allows more straight cement to be pulled out and replaced with between 10 and15 percent limestone. Limestone filler is not considered to be an SCM, and not everyone is convinced limestone fillers exhibit appreciable concrete strength or other technical properties. The addition of limestone has been a subject of considerable controversy within ASTM and industry circles for many years as summarized in 1988 by L.L. Mayfield in ASTM document STP 1064Carbonate Additions to Cement: "There are strong arguments on both sides of the question. The proponents claim a significant savings of energy during production without a degradation in quality and even cite improvements in some cement and concrete characteristics. The opponents charge that limestone merely acts as an adulterant, that strengths are reduced, and that the proposal should be abandoned on ethical grounds." ______________________________________________________________________________ Question: Type 1 PLC is being advertised as a new cement intended to help reduce carbon in the environment. How new is this, and how has ASCC addressed concerns about PLC? Answer: The cement industry in the US has been involved with substituting limestone for straight cement since long before the turn of the century. The original idea was to allow up to 5 percent limestone maximum in ASTM C 150. ASCC Hotline Operator Emeritus Ward Malisch wrote an article titled "Limestone Additions to Portland Cement: Pros and Cons...Revised ASTM Proposal Still Concerns Some Producers" for the Aberdeen Group in 1998 that accurately predicted the finger-pointing, NDAs and potential lawsuits we are seeing on jobsites today. Ward wrote "Although the National Ready Mixed Concrete Association hasn't taken a position on limestone additions, some individual producers have. Producers' major concern can be summarized in one statement: They will obtain no benefit from the revised cement specification, but will bear the brunt of customer complaints if the cements don't perform as claimed. The biggest worry is that strengths of cements containing limestone additions won't be equivalent to the currently available C 150 cements." In addition to the 1998 Malisch article, ASCC has expended considerable effort addressing potential problems associated with so-called "green" concrete that features reduction in OPC and replacement with SCM materials including fly ash, slag, and silica fume (not limestone). In 2011,ASCC Technical Division writers Ward Malisch and Bruce Suprenant described issues associated with high SCM mixes including slow set time, slow strength gain and finishing problems ("Be Wary of "Lean, Green" Concrete...Lowering the amount of portland cement in concrete can raise a number of issues", Challenging the System, Concrete Contractor Magazine). Recognizing these problems, ASCC collaborated with an industry advisory team including a concrete producer, a structural engineer, a concrete contractor and an admixture manufacturer in a study sponsored by the Charles Pankow Foundation titled "Assessing the Impacts of "Green" Concrete Mixtures on Building Construction." Published in 2013, the ASCC/Pankow study reported results of comprehensive cylinder and core testing performed on several "green" concrete mixes. As it turns out, the issues studied for the Pankow report are almost identical to the issues with PLC being reported today in ASCC Hotline calls and industry seminars. ______________________________________________________________________________ Question: What are the typical problems with PLC being reported from the field by ASCC concrete contractors today? Answer: According to our recent survey, suspected side effects of added limestone include increased water demand, slow set time (need for adding accelerator admixtures), low strength, crusting of top surface, more shrinkage cracks, more labor required to finish. Anecdotal reports of problems with sawcutting and adhesives not sticking are being vetted by the ASCC Technical Division. Longer-term issues with durability (e.g. wear resistance, polishing issues) are being investigated as well. To date, no issues with shotcrete applications were reported. ______________________________________________________________________________ Question: How do we know the PLC is not being placed and finished improperly by the concrete contractor? Answer: We don't. It is entirely possible that some of the reported problems are actually due to contractor error. This is the major downside to the introduction of NDAs on projects where PLC performance is suspect. We won't ever know the test results, who caused what, what it cost, and who got stuck cutting the checks. Many of the reports come from contractors who have been placing the same slabs for years, making the likelihood of error low. It is entirely possible the PLC needs to be cured a certain way, and that way has not been adequately specified in construction documents. We hear the industry has done a good deal of testing and preparing end users for the transition from OPC to PLC. But was that a full-scale 25,000 SF test pour representing a 3rd floor metal deck in the shade when the ambient air temperature is 40 degrees F? ______________________________________________________________________________ Question: How can ASCC concrete contractors protect themselves from cost impacts due to PLC being substituted for OPC? Answer: More and more contractors are told "It's here to stay, get used to it" and "We know there’s a learning curve". There are some regions in the US where Type 1 PLC is not being used yet ("but it's coming", they say). Sometimes it is easy to forget that one of our prime directives at ASCC is to be the best we can be in service to the Owner. If PLC is going to be mandated into a project, the Owner should be informed and prepared to carry an allowance to cover any repair and replacement costs associated with non-performance of the new material. If there is a "learning curve" that needs to be navigated, fair enough. But the Owner needs to be advised what preconstruction testing is required, how much time it is going to take, what test results constitute acceptance, and what the cost impacts are likely to be. For example, guidance for ASCC contractors related to cost impacts caused by slow concrete set time is provided in ASCC Position Statement #15: Setting Time Expectations for Hard-Trowel Finishing. In many cases, today's concrete contractor has sufficient experience with fly ash properties to be able to fairly estimate probable costs at bid time. But forward-pricing may not be possible for new, untested mixes, schedule changes, or cement changes made after a project is underway. ______________________________________________________________________________ Question: How can PLC present a potential risk to the end user? According to the industry, PLC has been used in Europe for 25 years and comprehensive testing has been performed. What does a contractor need to know about the PLC material risks? Answer: There are two issues with PLC on the manufacturing side that need to be considered. One, of course, is the quarry source of the limestone material. ASTM requires the limestone must meet certain chemical composition requirements before it can even be considered for use. The second issue arises in the grinding process. If the limestone is not ground to a certain fineness (a “Blaine number" for fineness, much higher than OPC), then all bets are off and the coarser-ground limestone will tend to act as an inert filler. According to a recent seminar presentation at World of Concrete, the grinding process for limestone "slows production and uses energy." In some cases, we learned, increasing the Blaine number "can cut production by as much as 40 percent." Could some grinding facilities be inclined to skimp on the grinding at the expense of performance? Is every grinding facility technically able to produce the required fineness? As Malisch pointed out 25 years ago..."Cement manufacturers acknowledge that manufacturing cement with limestone additions must be done properly to produce strength equivalents but say that the steps needed to optimize the process are achievable." Translation: You can't skimp on the grind. ______________________________________________________________________________ Question : How will concrete contractors be able to anticipate PLC issues in advance of placing a bid? Once a project starts, the chances of getting compensated for non-performing PLC are limited. Mix designs are typically not prepared prior to bid. Preconstruction testing during a two-week bid period is another pipe dream. Testing could easily require at least 56 days. How does the contractor proactively prevent a "learning curve" from turning into a costly "burning curve?" Answer : The best way to approach this is to ask your ready mix supplier if they are quoting concrete with Type 1L PLC additions. If they are, ask them for performance backup they propose to include with their mix design submittals, and how they intend to satisfy the ACI 301requirements for mix proportioning, prior break history, trial batch information and so on. Ask if they have been involved in projects involving suspect PLC. In many cases, the "new" PLC supplier will not have such backup. That is the time pre-bid RFI's (and bid qualifications) should be submitted to make the Owner aware there may be unexpected delays and testing costs associated with this "new" material that are beyond the contractor's control and unknown at bid time. _____________________________________________________________________________ Question: If PLC is indeed "here to stay", what can ASCC members do as the contractor part of this equation to help mitigate PLC transition issues on behalf of all project stakeholders? Answer: The most important part right now for ASCC members is collection of data and accounts of problems currently being experienced in the field. Please double check and make sure your ASCC survey has been completed and returned to the ASCC Technical Division. As we learned in the World of Concrete seminar, the concrete industry is being squeezed by a "rushed learning curve." Much more testing is required at the industry level to make PLC ready for prime time. In addition, seminar attendees were cautioned there will likely be a need for extensive end-user testing and experimenting, including mockup testing at the project level as well. "Special cautions" were given to attendees to beware of significant changes to PLC mix performance incases of "high-spec floor finishes, other bleed water-sensitive applications, interactions with ash &admixtures, water demand, and colder weather." (ASCC members please include accounts of any preconstruction testing efforts in your survey responses.) The question then becomes "Who is responsible for specifying, funding and testing the new PLC mixes?" It appears that much of the research performed for the 2013 ASCC/Pankow study maybe able to be applied to the PLC transition issues. Perhaps the cement industry will fund a similar collaborative study to help build on what we already know. _______________________________________________________ In response to the growing focus on reducing embodied carbon in the construction industry, ASCC is in the process of forming a Sustainability Committee to assist contractors in understanding and managing the upshots contractors are experiencing due primarily to material alterations. ASCC is working collaboratively with the Portland Cement Association and the National Ready Mixed Concrete Association to ensure the reduction of the carbon footprint of the concrete industry. rzuellig Wed, 15 Feb 2023 16:32:00 GMT f1397696-738c-4295-afcd-943feb885714:325 https://ascconline.org/Home/News/articleType/ArticleView/articleId/321/Mike-Hernandez-Hired-as-Technical-Director#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=321 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=321&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/321/Mike-Hernandez-Hired-as-Technical-Director January 25, 2023 – Michael G. Hernandez, P.E., DBIA, has joined the Technical Division of the American Society of Concrete Contractors (ASCC), St. Louis, MO, as technical director. This position oversees all technical activities of the organization including serving as the technical voice for ASCC in verbal and written communication, providing technical support for the members and the organization, and developing programming and resources to benefit the concrete contractor. rzuellig Wed, 25 Jan 2023 16:02:00 GMT f1397696-738c-4295-afcd-943feb885714:321 https://ascconline.org/Home/News/articleType/ArticleView/articleId/317/Guidance-for-Concrete-Contractors-13-in-a-Series#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=317 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=317&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/317/Guidance-for-Concrete-Contractors-13-in-a-Series Jim Klinger, concrete construction specialist The Voice Newsletter January 2023 ASCC Hotline Question: We are building a post-tensioned concrete high rise with a 30,000-sffootprint divided into three placements per floor level of 10,000-sf each. One such placement atthe 5th floor level is scheduled for Thursday, December 22. For supply-chain reasons, thisconcrete placement date cannot change. For holiday reasons, the project is shut down untilTuesday, December 27. In other words, the elevated slab will not be stressed until the fifth dayafter placement. The project specifications require stressing to be completed within 96 hours (fourdays) of placement. Weather in our region is normally forecast to range from 40 to 65 degreeswith moderate rain possible each day. The general contractor has acknowledged that stressing onthe industry-standard third day (Sunday, Dec. 25) would be inhumane, but is insisting we breakthe bank and mobilize a crew to stress on Monday, a company payroll double-time holiday. Thissame condition will occur the following week over the New Year's holiday. The approved PT slab mix design is 5000 psi at 28 days, 3000 psi at three days; the standard"high-early" mix with Orca low-shrink aggregate, which is popular in our market. We have had noissues with abnormal shrinkage cracking on the lower floors of this project, or on other projectsusing this same mix. Other than the post-tensioning steel, the slab is lightly reinforced. Theconcrete slabs are eight in. thick, with a typical bottom mild steel mat of #5 bars at 12 in. OCEWthroughout and top bars provided at columns and other locations. There is no call-out on thestructural drawings for supplemental mild steel shrinkage and temperature reinforcement. We understand the construction documents require the PT stressing be completed within 96 hoursof placement. Does the ASCC Technical Division know of any reason the slab stressing cannotwait until Tuesday? We would almost be willing to propose adding a layer of #4 bars at 12 inchesOCEW (top) for crack control in lieu of having to open the jobsite on double-time. Please advise. Answer: This issue intrigued us because we usually see requests for support of early PTstressing, not the other way around. According to ACI 318-19, section 25.9.4.5.4, the concretestrength must be at least 2500 psi for single-strand tendons before stressing to mitigate shrinkage cracking. Sometimes the LDP will allow stressing at strengths lower than 2500 psi for certain slabson grade and stage-stressing conditions. The Post-Tensioning Institute Journal (PTI, July 2019)tells us that their Post Tensioning Manual recommends PT be stressed within 72 hours and at aminimum strength of 3000 psi. In any event, all such requirements are aimed at closing early top-of-slab shrinkage cracks. Almost all of the PT-type projects we see for review feature requirementsfor stressing to be completed within the 72-to-96-hour timeframe. Since the mix design has been proven to reach high early strength with low shrinkage and noknown abnormal cracking, ASCC suggested placing the concrete slab, applying a second coat ofcuring compound, and covering the slab with curing blankets over the 96-hour holiday shutdown.On Tuesday, remove the blankets, inspect for cracks, and stress the PT. All costs associated withcuring compound, blankets, and possible crack repair to be by contractor. (N.B. Proposed courseof action was accepted by the LDP and the Owner). ______________________________________________________________________________ ASCC Hotline Question: We have just completed the third concrete placement out of 20 on thelargest contract our company has ever landed. The Owner seems impressed with the quality ofour finish work during job walks, but we have heard from the GC that there have been negativecomments about cracking in the slabs during private meetings. Our scope of work is to furnish andinstall rebar and concrete over a composite steel beam and metal deck substrate erected byothers. We are familiar with the ACI 302 note to Owners and designers regarding the inevitablecracking of certain concrete slabs, but we cannot find specific mention of slabs placed on metaldecks. Is there anything in the ASCC Technical Division library that can help us explain to theOwner that cracking of the metal deck slabs is normal? Answer: The design of the composite slabs on metal decks is covered by the Steel Deck Institute.In their design manual titled "C-2011 Standard for Composite Steel Floor Deck-Slabs", thefollowing guidance is given to designers: "Concrete floor slabs employing Portland cement will start to experience a reduction in volume assoon as they are placed. Where shrinkage is restrained, cracking will occur in the floor. The use ofappropriate types and amount of reinforcement for shrinkage and temperature movement controlis intended to result in a larger number of small cracks in lieu of a fewer number of larger cracks.Even with the best floor design and proper construction, it is unrealistic to expect crack free floors.Every owner should be advised by both the designer and contractor that it is normal to expectsome amount of cracking and that such occurrences do not necessarily reflect adversely on eitherthe adequacy of the floor's design or quality of the construction. Cracking can be reduced whenthe causes are understood, and preventative steps are taken in the design phase. The majorfactors the designer can control concerning shrinkage and cracking include cement type,aggregate type and gradation, water content, water/cement ratio, and reinforcement.” rzuellig Sun, 15 Jan 2023 15:19:00 GMT f1397696-738c-4295-afcd-943feb885714:317 https://ascconline.org/Home/News/articleType/ArticleView/articleId/314/Guidance-for-Concrete-Contractors-12-in-a-Series#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=314 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=314&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/314/Guidance-for-Concrete-Contractors-12-in-a-Series Jim Klinger, concrete construction specialist The Voice Newsletter November 2022 Full disclosure: I was ransacking the garage trying to find that one missing part from our George Foreman grill when I uncovered a couple of collector's items. There was a slightly dented blue metal hard hat- an old "Jackson hat", a real beauty- issued in 1979 when I took my first concrete construction job with Miller and Long. And then pops up another construction gem from 1979, a video of the movie "Steel", starring Lee Majors, George Kennedy, Art Carney and Jennifer O'Neill. To this day, "Steel" is the only movie ever made that actually takes place on an active construction jobsite**. Filmed during erection of the 22-story Kincaid Tower in Lexington, KY, the plot involves a retired steel superintendent (Majors) who returns to high-rise construction just in time to debut the industry's first three-day cycle by erecting nine floors worth of steel in three weeks after tracking down his old crew, beating the bad guys and at the same time making some serious time with Jennifer O'Neill. During a brief lull in the action and after several martinis, Oscar-winner Art Carney has just about had it with the steel construction business and pipes up with this piece of sage advice for the intrepid good guys: "I think it'll all be over soon, though. I don't think there'll be much high steel business anymore. I think it'll be replaced by reinforced concrete. But a man can't get very excited about cement". **N.B. Although this is technically correct, there are purists who will insist that there was a popular full-length music video that was filmed on an active concrete construction jobsite that deserves honorable mention. It was 1987, and the World Wrestling Federation (WWF) filmed the classic "Piledriver" to promote Koko B. Ware's upcoming match in "Saturday Night's Main Event" on an ASCC member jobsite in Oakland, CA. Many legendary WWF stars were there, from Vince McMahon to Hulk Hogan. In one sequence, the Hulkster can be seen at the end of the pump hose, placing concrete for an elevated podium slab. Similar to "Steel," these were committed to celluloid without the blessing or benefit of any corporate HR or Safety Dept. review. And Vince McMahon never did make good on his promise to deliver several cases of beer and other party favors to the concrete guys who had to clean up the mess after the video was filmed, the least of which was the pour crew who had to deal with the mess Hogan left on the deck. Top of column elevation tolerance: ACI 117-10 section 4.4.4 tells us that the top of wall elevation tolerance is plus/minus 3/4 inch. There is no top of column elevation tolerance specified. Columns that frame into slabs or beams are usually formed and placed so the column concrete at each construction joint protrudes slightly higher than the elevation of the formed beam or slab soffit. This allows the soffit formwork to butt into concrete and minimize loss of concrete at that opening. When column cold joints are below the slab or beam soffit, forming at the opening in the form soffit is more complex and more concrete leakage is likely. For these reasons, ASCC contractors often place the top of columns (and walls that frame into slabs) on the plus side of that tolerance. Engineers may require the concrete contractor to chip out concrete above the adjacent slab or beam soffit due to a belief that the slab shear capacity is reduced by the column "overpour" intrusion into the slab (or beam). Unfortunately, this requirement is not included in the construction documents, is usually enforced by inspectors on-site, and results in additional cost to the contractor. ACI 318-19 "Building Code Requirements for Structural Concrete," does not include any guidance for handling this issue, and we cannot find published data regarding the intrusion of "overpoured" column concrete on shear capacity. The ASCC Technical Division is looking for your experience with "overpours" at top of columns. Have you had to chip column concrete out? Do you have photos? Specifically photos of how the column is formed when the column top is below the soffit form and of how bad the concrete divots look on the column when it is below the soffit. Has the EOR ever put in writing why and how far you had to chip the concrete down? We know this is a long-standing cause of confusion in the industry and are working to help resolve this to eliminate recurring hassles and cost impact. Let us know. Keep those cards and letters coming. _____________________________________________________________________________ ASCC Hotline Question: We are scheduled to complete several projects here in the next few months, including sidewalks and exterior slabs. Are there any papers or articles we can share with the project Owners that describe the ill effects of deicers on young concrete? Answer: There are several sources that can be cited. The first is ACI 302.1R-15 Guide to Concrete Floor and Slab Construction. In section 13.5-Scaling, ACI tells us that scaling can be caused by use of deicing chemicals because "deicers lower the freezing point of water that can increase the number of freezing-and-thawing cycles and can increase the propensity for resaturation of concrete during the thawing period." ACI 302 section 8.4.3 also tells us "the use of any deicing chemicals is not recommended in the first year of slab service." The Portland Cement Association (PCA) recommends a "drying period should be at least 1 month of relatively dry weather before the application of deicing salts." Even application of sealers to new concrete can be as risky as gas station sushi. According to the PCA, "Concrete placed in the late fall should not be sealed until spring because the sealer may cause the concrete to retain water that may exacerbate freeze-thaw damage." rzuellig Tue, 15 Nov 2022 19:02:00 GMT f1397696-738c-4295-afcd-943feb885714:314 https://ascconline.org/Home/News/articleType/ArticleView/articleId/319/Guidance-for-Concrete-Contractors-11-in-a-Series-Discoloration-Due-to-Slag-Cement#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=319 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=319&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/319/Guidance-for-Concrete-Contractors-11-in-a-Series-Discoloration-Due-to-Slag-Cement Jim Klinger, concrete construction specialist The Voice Newsletter October 2022 Question: We poured a cast-in-place concrete residential basement wall one week ago. The mix was a standard 6-sack footing and wall mix typically specified in our local market, 3000 psi at 28 days with a design water-cementitious ratio of 0.55. We stripped the walls this morning, and were surprised to see the wall surfaces stained blue as depicted in the photos below. We have been using the same type of form panels and form release for years and have never seen such discoloration. The homeowner is demanding an explanation. What can ASCC tell us? Answer: Our review of your approved mix design submittal indicates that the concrete mix has been proportioned with 366 lbs. of Type II cement (ASTM C150) and 198 lbs. of Grade 120 slag cement (ASTM C989). Put another way, this is a 35 percent slag mix, and therein lies our answer. According to the Slag Cement Association (SCA) "Info Sheet IS-10", the mottled green or blue-green areas you are seeing are known as "greening", caused by a chemical reaction between sulfide sulphur in the slag cement and compounds in the straight cement. Greening is cosmetic only; the temporary discoloration does not affect strength, permeability or durability. No special treatment needs to be applied to make this go away. Greening typically disappears once the concrete surface is exposed to air and direct sunlight. The key is giving the wall a chance for the surface to oxidize. Conditions that may cause slower oxidation rates could include cold, wet weather, sealed surfaces, and so on. In most cases, however, the exterior surfaces should return to normal within a week. The interior of the wall section, however, since it isn't exposed, could stay blue indefinitely. The Slag Cement Association website currently has 29 technical "Info Sheets" that can be downloaded for free, covering all aspects of working with slag cement from mix design proportioning to sawcut joints to greening. All should be of interest to ASCC members.  _____________________________________________________________________________ Question: We experienced readymix material shortage delay issues at the end of 2021 and the first part of 2022 as described by Cory Lee in the September 2022 ASCC VOICE. We are currently trying to close out a project and have requested an equitable price adjustment from the Owner in an attempt to recover cost impacts associated with supply-chain issues that were totally out of our control. The Owner is asking us to provide proof that there was indeed a break in the supply-chain that caused our project to be delayed. Does ASCC have literature or articles from that time that can show this was a real shortage? Answer: We searched for literature you might use to support your position. The best way to proceed is to document the shortage or supply-chain issues through your readymix supplier and the cement sources identified in your approved mix design submittals, since those would be the most project-specific. For regional information regarding cement economic trends, the Portland Cement Association (PCA) website has a wealth of resources available in various media. Some of the economic reports have a subscription-type paywall, but there are many complimentary reports that may contain the regional data you are seeking. What you are going to find straightaway is the PCA economic reports are extremely comprehensive in scope, covering monetary policy, wage trends, fuel trends, housing market trends and other factors that either directly or indirectly affect the supply, demand and distribution of cement. There are no doubt other ASCC members who have similar experiences with tight cement market conditions. After reviewing the information from your suppliers and the PCA reports, please let us know how your negotiations turned out. We also recommend you sending a copy of the recently-published ASCC Position Statement #45 titled "Managing Concrete Projects: Concrete/Steel Price and Delivery Volatility Risks" to the Owner, which is a reminder that there are indeed unpredictable and unstable market factors beyond the control of the concrete contractor that are fair game for an equitable price adjustment. rzuellig Sat, 15 Oct 2022 14:24:00 GMT f1397696-738c-4295-afcd-943feb885714:319 https://ascconline.org/Home/News/articleType/ArticleView/articleId/288/Guidance-for-Concrete-Contractors-10-in-a-Series#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=288 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=288&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/288/Guidance-for-Concrete-Contractors-10-in-a-Series Jim Klinger, concrete construction specialist The Voice Newsletter September 2022 Question: We are working on a large city public works project that has us placing our first foundation concrete in about a month.  We are inundated with design changes in the form of large "Bulletins" and sketches (aka "SKs") that are returned to us as part of Requests for Information (aka RFIs). In turn, we must transmit all project documents to our subcontractors, which includes detailers for rebar, PT and formwork. Each of those stakeholders must quickly determine if there are any cost or schedule impacts to their scope and, perhaps most important now, if rebar placement drawing submittals are going to be affected. In many cases, the only way we can tell if design drawings have been updated is by checking the dates in the title blocks.  We have advised the GC that we expect all drawing changes to be clouded, and that all changes to our scope be issued with a written narrative describing such changes. Are there any industry standards we can cite that support our expectations? Answer: The Owner gets maximum time and cost benefit when information flows up and down the food chain in an efficient and professional manner. This includes the design team issuing Bulletins, Addenda, RFIs, sketches and other contract changes with all drawing changes clouded and all changes clearly described in a written narrative. This is true not only during budget and bid time (estimators, take note) but also holds true for all sides during the construction phase as well. For ASCC members, we are aware of two industry references that describe scope revision documents and how they should be prepared by designers and detailers. According to the Council of American Structural Engineers (CASE) Document 962-F A Guideline Addressing the Bidding and Construction Administration Phases for the Structural Engineer: "Changes to the construction documents...should be clearly identified with dated revision numbers and "clouding" in the case of drawings.  All changes must be documented in writing and delivered to everyone that has received a copy of the construction documents...including contractors, subcontractors, consultants and Owners.  Prompt issuance and clear description of the changes, communicated to all interested parties, are essential to minimizing their impact on cost and schedule." On the other hand, concrete contractors and their detailers should be aware that they can be held to the same standard regarding completeness of their rebar placing drawings, formwork shop drawings and other documents prepared for submittal to, and review by the design team.  According to Joint ACI-CRSI (American Concrete Institute - Concrete Reinforcing Steel Institute) document ACI 315R-18, Guide to Presenting Reinforcing Steel Design Details, section 3.3- "General Cautions," that applies to rebar and PT detailers: "All revisions to drawings should be clouded. Be as specific as possible when putting a cloud on a drawing.  Place a cloud around each revision, rather than a large cloud around several revisions.  Remove all previous clouds from a drawing before initiating a new revision.  Clearly annotate the revision on the revision list at the side of the drawing". ______________________________________________________________________________ Question:  We placed a CIP (cast-in-place) concrete slab two months ago. Part of our scope included placing anchor bolts for some follow-on metal building framing.  Supply, layout and pre-pour anchor bolt location survey checks were performed by others.  Today, we received a substantial backcharge from the GC, stating that the metal building erector had to provide shims to make his framing work. We acknowledge that our concrete finishing work was not perfect, but the slab passed the F-number test performed by the Owner, and there is no way any of our finished concrete top of slab elevation was outside of the ACI 117-10 tolerance envelope of plus or minus 3/4 inch in section 4.4.1.  How should we respond to this backcharge? Answer:  For structural steel columns and baseplates per se, steel shim packs are routinely used by steel erectors to level column base plates.  This allows steel column erection loads to get transferred to the concrete foundation without loading the anchor rods. Your case is slightly different e.g. a metal building on an elevated concrete slab, not a steel column bearing on a concrete footing.  So does that make a difference and allow one to transmute cheap steel shims into gold? Not so, according to the Metal Building Manufacturer's Association.  As it turns out, the issue of shims is addressed in straightforward manner in the Metal Building Systems Manual, section 6.10, titled "Correction of Errors and Repairs" as follows: "The correction of minor misfits by the use of drift pins to draw the components into line, shimming, moderate amounts of reaming, chipping and cutting, and the replacement of minor shortages of material are a normal part of erection and are not subject to claim." (N.B.  The interface between a steel structure and whatever concrete it sits on is often a murky no-man's land.  Example: grout and grouting under column base plates is a scope item that isn't likely to be found addressed in either steel or concrete design manuals. For ASCC members who have grouting of steel column base plates in your scope, make sure you understand the timing of the grout placement relative to the erection schedule.  This is a design item that should be part of an Owner-approved erection stability plan provided to the concrete contractor.) ______________________________________________________________________________ ASCC Webinars:  Thanks to Dr. Ken Hover for presenting the latest ASCC webinar titled "When Does Rebar Corrode in Concrete, and Why?" on Sept. 14.  Previous webinars presented by Dr. Hover include "How Well Do We Know In-Place Concrete Strength" and "Shoring and Re-shoring." More than one hundred past ASCC webinars are archived on our website.  General topics we have covered include Concrete Construction, Decorative Concrete, Polished Concrete, Business Management, Paving and Parking Lots, and Safety. rzuellig Thu, 15 Sep 2022 15:31:00 GMT f1397696-738c-4295-afcd-943feb885714:288 https://ascconline.org/Home/News/articleType/ArticleView/articleId/277/Guidance-for-Concrete-Contractors-9-in-a-Series#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=277 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=277&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/277/Guidance-for-Concrete-Contractors-9-in-a-Series Jim Klinger, concrete construction specialist The Voice Newsletter August 2022 Question: We are bidding the concrete portion of a steel bridge job and noticed the term "bold exposure" mentioned in the Div. 5 construction documents. We aren't familiar with this term, and how it might affect our concrete scope. Answer: The steel girders are called out to be fabricated with ASTM A588 weathering steel, also known as "COR-TEN" steel (taken from CORrosion-resistant, high TENsile strength). To oversimplify enormously, this material was developed to rust on purpose to protect itself from further rust. This idea works as long as the girder is “boldly exposed” to an environment that will allow a thin layer of rust to form on its outer surface. In this case, bold exposure means rain washed-sun dried. In reality, it probably takes several cycles of rain-wash and sun-dry before a protective oxide layer is fully formed. State highway departments typically specify weathering steel for girders and other steel members to eliminate initial painting cost and reduce future maintenance costs. Architects and artists use COR-TEN material for exposed steel buildings and sculptures because of the pleasing appearance of the patina. The key here is that weathering steel must be boldly exposed and allowed to dry. If that does not happen, then the whole plan backfires and the steel will corrode. (N.B. #1: A notorious example of this is the Aloha Stadium in Honolulu which was built with COR-TEN steel in the 1970s. Many of the main structural members were designed such that they collected daily rainfall but were never allowed to dry. It was a disaster.) For your project, the only "exposure" we see is a significant exclusion item related to the timing of your work and the follow-on placement of the steel. We suggest you exclude all work associated with rust stains that are likely to appear on any and all work you placed for the obvious reasons described above. ______________________________________________________________________________ Question: Does ASTM C856 explain what the w/cm ratio is in a core? I thought I remember reading an article at some point that said this was one of the things petrographic analysis could not show. Answer: ASTM C856 Standard Practice for Petrographic Examination of Hardened Concrete recognizes that there are many factors that may influence the w/c and w/cm of the concrete paste, including amount of original water, free water introduced by aggregates, tempering and retempering water, bleeding and vibration after concrete placement, and so on. Section 13.3 states the following:  13.3 Because of the variable nature of pastes, age of pastes, and exposure to a variety of external influences, there is no generally accepted standard procedure that employs microscopical methods for determining the w/c or w/cm of hardened concrete. The issue of petrographic analysis reports prepared to determine contract compliance was explored in some detail by Bruce Suprenant and Ward Malisch in an article titled "How to Evaluate Petrographic Reports...Separating Facts from Conclusions." It appears that estimates of w/c and w/cm might be made by some petrographers, but their reports and conclusions should always be carefully reviewed ...and possibly challenged. (N.B.: During the course of researching this, we found one guide to petrography written by a certain state highway official who advises "The petrographer must use good judgement and a sense of justice in selecting the portion of the specimen" to be tested. Further guidance tells us his state department does not perform petrographic analysis "on samples suspected of having a normal or low water-cement ratio... we have never had to report a case where the cement content indicated that a significant excess of cement was added or that a significant amount of water was omitted.") ______________________________________________________________________________ Question: We have misplaced a few anchor rods just outside the ACI-117 tolerance for anchor rod assemblies. We already know from discussing this with the steel erector that the fix will involve enlarging holes in the column baseplate and then welding plate washers to the baseplate after the column has been set. It is now on us to prepare a proposed fix submittal to the structural engineer for approval. Isn't there a "canned" collection of typical fixes for anchor rod mistakes like this? Answer: As it turns out, the American Institute of Steel Construction (AISC) has several resources, many of them free, that are of value to ASCC members. In this case, there is an AISC document at this link titled "Field Fixes- Common Problems in Design, Fabrication and Erection- Solutions and Prevention." rzuellig Mon, 15 Aug 2022 14:38:00 GMT f1397696-738c-4295-afcd-943feb885714:277 https://ascconline.org/Home/News/articleType/ArticleView/articleId/274/Guidance-for-Concrete-Contractors-8-in-a-Series#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=274 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=274&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/274/Guidance-for-Concrete-Contractors-8-in-a-Series Jim Klinger concrete construction specialist The Voice Newsletter July 2022 Full disclosure: Quite a lot of ASCC Hotline calls include requests for technical/educational backup members need to submit to general contractors, inspectors, structural engineers, or even Owners. In order to be effective, such backup should be limited to a few pages, similar to our ASCC Position Statements. In many cases, this documentation can be quickly extracted from the vast archives here at the ASCC Technical Division. But there is also a wealth of downloadable information--most of it free --that members can access online to supplement their own in-house, technical resource database. Links to some of the more prolific sources of concise, easy-to-digest technical documents that members and their customers should find valuable are provided below. Insider's note: The descriptions below are brief and may be misleading to the degree that such a short description might warrant an equally short perusal once one arrives at each web page. A more accurate estimate would be several hours attention per location--minimum--just to understand what is being presented at each and their corresponding implications. Please feel free to call the Hotline with questions. ______________________________________________________________________________ National Ready Mixed Concrete Association (NRMCA) The National Ready Mixed Concrete Association maintains four series of comprehensive technical resource support documents referred to in shorthand as CIP, SIP, TIP and PIP. The CIP series (Concrete in Practice, 45) are typically short, two-page information sheets that cover topics ranging from dusting, scaling and cracking to strength testing and aggregate popouts. The SIP series (Specification in Practice, 5) contains guidance aimed at designers and ready mix personnel. The TIP series (Technology in Practice, 22) are 2-to-8 page detailed discussions of topics such as core testing, maturity testing and strength test evaluation. The PIP series (Pervious in Practice, 4) discusses pervious concrete specifications, mix proportioning, contractor certification and acceptance testing. https://www.nrmca.org/association-resources/research-and-engineering/ ______________________________________________________________________________ Concrete Reinforcing Steel Institute (CRSI) The Concrete Reinforcing Steel Institute collection contains more than the name implies. Obviously there is educational material regarding reinforcing steel, ranging from allowable rust on rebar, to bending rebar in the field, to epoxy-coated rebar, to tolerance compatibility in cast-inplace concrete construction. But there are also articles regarding the high-strength steels currently available, along with numerous case studies showcasing reinforced concrete projects that have been successfully constructed using various reinforcing steel materials and techniques. These are the free publications. There are also design guides, online courses, and other resources that come with a fee. crsi.org _____________________________________________________________________________ Post-Tensioning Institute (PTI) The Post-Tensioning Institute resource center contains links to Frequently Asked Questions (FAQ), Technical Notes, and to selected articles from the Post-Tensioning Institute Journal. Articles usually found interesting to ASCC Hotline callers include issues with PT cable elongations, barrier cables, repair of unbonded PT tendon sheaths, and repair of PT cables broken during construction. https://www.post-tensioning.org/education/publications/faqstechnotes.aspx ____________________________________________________________________________ Association of the Wall and Ceiling Industry (AWCI) Now here's a case where sometimes the only way to cure claustrophobia is by thinking outside the box. Every month, the AWCI publishes a free,  downloadable magazine titled "Construction Dimensions." Right off the bat it contains a monthly column, "Estimator's Edge" by Vince Bailey, which any estimator should enjoy, regardless of trade. Other columns and articles, even though obviously geared to drywall and follow-on work, have information of value to contractors regarding project cost, schedules, safety, management, and technology. https://www.awci.org/technical rzuellig Fri, 15 Jul 2022 19:11:00 GMT f1397696-738c-4295-afcd-943feb885714:274 https://ascconline.org/Home/News/articleType/ArticleView/articleId/269/46th-Position-Statement#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=269 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=269&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/269/46th-Position-Statement July 11 – ASCC has published its forty-sixth Position Statement, “Water-Cementitious Material Ratio for Concrete to Receive a Trowel Finish.” ASCC Position Statements clarify the concrete contractors’ point of view for architects, engineers, owners, and others. rzuellig Mon, 11 Jul 2022 15:36:00 GMT f1397696-738c-4295-afcd-943feb885714:269 https://ascconline.org/Home/News/articleType/ArticleView/articleId/268/45th-Position-Statement#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=268 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=268&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/268/45th-Position-Statement June 23 – ASCC has published its forty-fifth Position Statement, “Managing Concrete Projects: Concrete/Steel Price and Delivery Volatility Risks.”   rzuellig Thu, 23 Jun 2022 20:14:00 GMT f1397696-738c-4295-afcd-943feb885714:268 https://ascconline.org/Home/News/articleType/ArticleView/articleId/262/Guidance-for-Concrete-Contractors-7-in-a-series#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=262 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=262&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/262/Guidance-for-Concrete-Contractors-7-in-a-series Jim Klinger, concrete construction specialist The Voice Newsletter May 2022 1. Hotline question: "The Owner has asked us to pick up some post-award retrofit scope and attach the base contract concrete structure to an adjacent building. This added scope includes epoxying reinforcing bars drilled overhead into the soffit of an existing concrete roof beam. We have been told there are special requirements for the installation and inspection of such overhead drill/epoxy work. Please advise for estimating and scheduling purposes.” Hotline answer: There are indeed special requirements for both the installation and the inspection of anchors installed horizontally or "upwardly inclined" (defined as being installed clockwise from 9 o'clock and 3 o'clock"). Your concrete estimators will definitely need to consider the following excerpts taken from ACI 318-19, as follows, before pricing this work: Section 17.2.2 "Adhesive anchors shall be installed in concrete having a minimum age of 21 days at time of anchor installation.” Section 26.7.2(d) "Post-installed anchors shall be installed by qualified installers.” Section 26.7.2(e) "Adhesive anchors identified in the construction documents as installed in a horizontal or upwardly inclined orientation to resist sustained tensile loads shall be installed by certified installers.” Section 26.13.1.6 " The installation inspection of all adhesive anchors shall be performed by a certified inspector.” Commentary section R26.13.1.6..."installation in an upward position...poses challenges to the installer and requires particular attention to execution quality as well as an enhanced level of oversight. It is required that these anchor installations be inspected by a certified inspector who is continuously present when and where the installations are being performed.” Since you already have the job, ASCC suggests you arrange a meeting with the engineer to ensure all stakeholders- including project inspectors- understand the scope at hand. In all likelihood the work will have to be installed by someone employed by your company who is an ACI Certified Adhesive Anchor Installer (AAI). If you do not have an ACI Certified AAI on your payroll, check with your local ACI Chapter for their certification course schedule. There are several parts to the certification, including a closed-book examination and a hands-on performance examination featuring application (injection) of various adhesives into plastic tubes that are then cured, cut open and evaluated for grading purposes. Link to a short ACI video showcasing the certification process. Note that there might be adhesive manufacturers who may be able to supply product data that supports use of a product in concrete that is less than 21 days old. There may be engineers who can justify drilling and epoxying bars at seven days with supporting pullout testing. Each project will be different, and each engineer may have pull test or other requirements that could delay installation of subsequent work. All of these potentially schedule-critical topics are fair game for discussion and should be understood by all stakeholders before any ASCC member is asked to estimate the cost of such work. ______________________________________________________________________________ 2. Hotline question: We are building a ramp in an underground parking garage. We proposed to form the first portion of the ramp from elevation zero to jump-off wall (about two feet high) with scrap lumber. In other words, we would consider this "lost form" or "void form" which would never be stripped out and would always remain under the ramp. Since the space is so small and unusable, we figured no one would care. The structural engineer ok'd our submittal, but the architect blasted us out of the water, saying our submittal stank to high heaven. They insist we use high-density styrofoam, which is expensive. Is the architect correct? Hotline answer: This same question crosses our desks here from time to time. We cannot find any mention of any long-term olfactory formwork problems in industry literature other than a brief mention in the ACI/ASCC Contractor's Guide to Quality Concrete Construction. So we have to rely on our own experience over many years in the business. And in this case, the noses know. Your architect is correct. ____________________________________________________________________________ 3. Hotline question: We have been asked to bid a project that includes structural walls that snug up to existing structural slabs. One possible way to build these would be to pump concrete from the bottom up. If we pumped SCC, how would the formwork pressure be calculated? Hotline answer: This is a good one for your formwork engineer. In general, the prevailing wisdom in the concrete industry is that no matter what, one always designs for full liquid head, plus the impact load on the formwork imparted by the surge of the pump. According to ACI 347R-14 Guide to Formwork for Concrete, Section 4.2.2.4, "If concrete is pumped from the base of the form, the form should be designed for full hydrostatic head of concrete plus a minimum allowance of 25 percent for pump surge pressure. Pressures can be as high as the face pressure of the pump piston; thus, pressure should be monitored and controlled so that the design pressure is not exceeded.” The 25 percent minimum allowance for pump surge is consistent with the recommendations made in ACI PRC-237.2-21 Form Pressure Exerted by Self-Consolidating Concrete: Primary Factors and Prediction Models-Report. In general, pump ports are secured to the wall forms about a foot up from the base of the wall, spaced about 10 feet apart. The ports are fitted with so-called sliding gate "slam" valves, possibly proprietary in nature, and opened and slammed shut with a sledge hammer, hence their name. See photograph below of a full-scale wall mockup featuring slam valves, taken during a concrete placement, and a second photograph showing a typical patch item that remains at each pump port once the wall forms have been stripped.      When using the "pump from below" method, ASCC recommends the SCC mixes be tested at least once in a full-scale wall mockup and trial batched and pumped at least once before that. This is no time to skimp on costs or details. Inside the wall, reinforcing steel, embeds, conduits and so on need to be coordinated and planned well in advance of placement. Plumbing sleeves cannot be located next to pump ports, for example. Reinforcing steel may need to be adjusted to accommodate both the ports and the expected flow of the SCC, especially in walls featuring congested reinforcing steel. ASCC recommends early collaboration between the formwork designer, the reinforcing steel detailer, the concrete contractor and the project LDP when the pump-from-below method is proposed for cast-in-place walls. rzuellig Sun, 15 May 2022 14:03:00 GMT f1397696-738c-4295-afcd-943feb885714:262 https://ascconline.org/Home/News/articleType/ArticleView/articleId/258/Guidance-for-Concrete-Contractors-6-in-a-Series#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=258 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=258&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/258/Guidance-for-Concrete-Contractors-6-in-a-Series Jim Klinger, concrete construction specialist The Voice Newsletter April 2022 Full disclosure: A wise man once offered the following bit of advice on how best to navigate the uncertain waters of concrete construction. "It's easy," he said, "you just have to position yourself to get lucky". So consider if you will, the following Hotline call fielded by the ASCC Technical Division last November that showcased the long-standing need for industry guidance for F-number testing of broom and swirl-type textured finishes. As recounted below, what started out as a routine call grew into a three-part test program sponsored by the ASCC Foundation. As you'll see it provides immediate value to ASCC members, and will help bring improvements to our industry. (N.B. Due to VOICE space limitations, there really is no good way to do this the justice it deserves. This writer has romanced certain passages below, but only for purely technical reasons). ____________________________________________________________________________ Hotline question: "We recently completed concrete placement at level three of a 10-story, post-tensioned (PT) parking garage. The building geometry is based around a single-threaded helix. The typical floor plans show no level spots, meaning the structural frame is really one continuous ramp that slopes from the foundation mat to the roof. Approximate building footprint is 21,000 SF. The Division 3 specifications call for a "non-slip, non-skid, swirl-float" finish at all vehicle traffic and parking areas. Feedback noted in owner/design team site visit reports indicates satisfaction with all work placed to date. The ramp slabs are boldly exposed to rainfall during construction and no ponding of water has been reported, even after the elevated PT slabs have been stressed and the supporting formwork cycled. Due to misunderstandings at bid time, no one on the project team included ASTM E1155 Flatness and Levelness Testing in their scope. As a result, the top surfaces of the first three floors were never tested for flatness (due to the "all ramp" slope condition, levelness testing does not apply). Since the Owner and Architect visit the jobsite weekly and are happy with the work in place, the lack of flatness testing went unnoticed until someone in the GC food chain scrutinized Section 03 35 00 CONCRETE FINISHING, which arguably assigns ownership of said testing to the concrete contractor. This is a public works project, which did not allow qualifications to be listed on the bid form. We have enjoyed a successful working relationship with the key project stakeholders for many years and have agreed to pick up the flatness testing scope for floors four through the roof; confident that an equitable commercial arrangement will eventually be crafted that will make us whole. That being said...we have examined the project specifications, and are not sure what flatness test criteria we should provide to our newly-hired test agency, especially for slabs featuring such a rough-textured finish. We have been building concrete parking structures for many years and have never seen flatness tested on swirl finish jobs. Acceptance criteria was usually based on symmetry of the swirl pattern and sometimes water testing to detect ponding or birdbaths. If slab thickness was in question, that could easily be spot-checked at blockouts, sleeves, edgeforms and so on. Please advise how we should proceed with direction to the test agency.” Specification requirements: A review of the Division 3 specifications turned up the following: "Comply with ACI 117 for local flatness/levelness tolerance measured in accordance with ASTM E1155. Specified Overall Value (SOV) of F/F=30 and Minimum Local Value (MLV) of F/F=25 ". "Suspended concrete slabs: F/F: SOV=35  MLV=25 " Resolution: Based on recommendations made by the ASCC Technical Division, the concrete contractor submitted an RFI requesting that the flatness testing be waived. The rationale for this request is that there has always been confusion in the industry regarding the inherent variability in the surface quality of textured, non-skid applications such as swirl and broom finishes. In addition, no guidance for such testing appears in ACI 117-10 Specification for Tolerances for Concrete Construction and Materials. The design team was advised that based on experience and available ACI and other industry documents, the specified flatness criteria were likely to be unachievable. A conference call with the designers was held. The design team would not waive the flatness testing but did acknowledge the "ramping slabs as non-critical" and reduced the specified flatness SOV to F/F=20 and MLV to F/F=15. The designers again expressed satisfaction with the work in place and agreed it was fit for purpose based on appearance and lack of ponding. The concrete contractor directed the test agency to start ASTM E1155 Flatness testing using the adjusted SOV=20 and MLV=15 criteria. After testing two successive placements, the reported F/F combined scores were 17.90 and 15.84, just under the SOV required value of F/F=20. After reviewing this test data, the design team reconsidered the RFI request for waiver and agreed to cancel further testing. ______________________________________________________________________________ The Rest of the Story (condensed version): Within a few days of the Hotline call, we learned that the ASCC contractor member was planning to replace a concrete access road in their maintenance yard. Several thousand square feet (SF) of 6-inch thick slab was on the books for replacement.  We requested permission to carve out a 20 ft. by 80 ft. section of the area for testing. The test slab was reinforced with #4 bars at 14-inch centers, placed over tightly compacted aggregate base. No vapor barrier was used. Prior to placement of reinforcing steel, the subgrade elevation was recorded with a laser scanner. The test panel was subdivided into four equal sections: bull float finish, machine float finish, broom finish and swirl finish. During concrete placement, the four test areas were separated by tooled, contraction joints. After placement, the top of each test panel slab section was tested for flatness by the test agency using a dipstick. At the same time a companion laser scan was performed by the concrete contractor. Once the laser scan of the top surface was complete, we were able to use the test slab not only to test flatness of textured finishes, but to collect test data on slab thicknesses using laser scanning, impact echo, ground penetrating radar (GPR), and drilled core measurement methods as described below. The top surface elevations were subtracted from the bottom base surface elevations to obtain concrete thickness at 1-ft. grid intervals. This resulted in about 1700 thickness values for the test panel. But how good was this data? We could find nothing in the literature comparing laser scan thickness data to any other methods. The contractor owned a ground penetrating radar device which was then used to scan the slab for thickness. About the same time, the ASCC Foundation funded the purchase of an impact echo device to allow members to collect slab thickness data. That device was loaned to the contractor who took impact echo thickness measurements from the test panel. Finally, with all this data, we felt this investigation would benefit from the “gold standard” in slab thickness measurements—cores. We requested, and the ASCC Foundation funded, the drilling and measuring of 30 cores in accordance with ASTM C174 “Standard Test Method for Measuring Thickness of Concrete Elements Using Drilled Concrete Cores.” But what about measuring cores by ASTM C1542 “Standard Test Method for Measuring Length of Concrete Cores?” Once again, the Foundation funded the measurement of the same 30 cores by both the jaw caliper and ruler procedures in ASTM C1542. ACI-ASCC 117 Tolerances is updating its tolerance specification and has appointed a new subcommittee on measurement protocols. The slab thickness data was presented to the main 117 committee at the Orlando convention in March 2022. While 117 provides for only core and impact echo thickness measurements, other methods are being used to investigate slab thickness. This presents a most interesting and difficult question—how should nondestructive test methods used to determine slab thickness be compared to a thickness tolerance originally established by core measurements? _____________________________________________________________________________ Results of the testing and an in-depth discussion titled "F-numbers and Textured Concrete Surface Finishes" will appear in the May 2022 issue of Concrete International as part 1 of a 3 part series. Parts 2 and 3 are being drafted and are slated to be published later this year. Thanks to ACI Honorary Member Bev Garnant and the ASCC Foundation for supporting the test program, arranging funding on short notice, and helping to position us to get lucky. rzuellig Fri, 15 Apr 2022 14:44:00 GMT f1397696-738c-4295-afcd-943feb885714:258 https://ascconline.org/Home/News/articleType/ArticleView/articleId/252/Guidance-for-Concrete-Contractors-5-in-a-series#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=252 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=252&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/252/Guidance-for-Concrete-Contractors-5-in-a-series Jim Klinger, concrete construction specialist, The Voice Newsletter March 2022 Full disclosure: Over the past year, the intrepid ASCC Technical Division research staff has been assigned to cover a wide range of stories that directly affect the ASCC membership at large. In some cases, the background sources for these articles did not come from the concrete construction business per se. For example, we relied on the sensational, crisp legal writing of attorneys Loulakis and McLaughlin over at ASCE's Civil Engineering Magazine to explain the intricacies of the Spearin warranty decision as a basis for our Feb. 2021 VOICE. We again turned to our ASCE colleagues for assistance with our COVID claims cost recovery story that ran in March. When we needed a touch of wry humor to kick off our VOICE series on concrete estimating in November 2021, we found inspiration courtesy of Vince Bailey, a seasoned drywall guy who writes the "Estimator's Edge" column for "Construction Dimensions", the AWCI (Association of the Wall and Ceiling Industry) monthly magazine. This month's source comes to us in a roundabout way, discovered while researching related topics for future ASCC Position Statements. As you read into it, you'll quickly see the source as clear as glass. _____________________________________________________________________________ What follows is adapted from a presentation prepared by attorney Courtney Little, president of the American Subcontractors Association (ASA) titled “The Top Ten Clauses When Negotiating Contracts”. This presentation lays out typical situations we all encounter when administering our subcontracts with GCs and Owners, and typical work-arounds and carve-outs we might use during the back-and-forth of subcontract negotiations. Unfortunately, the ASA presentation is a bit too long to reprint verbatim in The Voice, but it is readily available in the public domain. We encourage ASCC members to study the ASA presentation in its entirety at the link provided below. ______________________________________________________________________________ When the GC says “This Owner is very demanding and doesn’t always know what it wants. We need you to stay flexible when considering these new documents.” The ASCC sub can say “Like you, we are committed to giving the Owner the best job possible. But the documents currently contain many added cost items that we didn’t know about when we bid to you. We can either work out our pricing with you on those items or go back to the earlier requirements." When the GC says “We both know what your trade involves. I don’t think we need to define every dot and tittle now." The ASCC sub can say “You’ll see that our bid submission was very specific about what it covered. We either need to incorporate the description of work in my submission and the price into the subcontract, or, we need to delete from the subcontract those items that were added." When the GC says “We can address these concerns later as the job progresses." The ASCC sub can say “I know we’re both committed to making this project go as smoothly as possible. It’s best to address these potential problems now, instead of waiting for problems to arise." When the GC says “You are going to have to be flexible and adjust your schedule as necessary." The ASCC sub can say “I understand that you may have to make subcontract schedule changes, but I can’t agree in advance to adapt and adjust my work to suit your needs without the right to more money and an extension of time for me to finish my work." When the GC says “Don’t worry. We’re going to have everything ready for you." The ASCC sub can say “I can’t make the schedule unless your jobsite utilities are ready on time and my submittals are approved and returned promptly." When the GC says “We don’t pay for acceleration. You just have to be flexible." The ASCC sub can say “If my work doesn’t start on time because of project delays, I’ll need to be paid for my acceleration costs or be allowed more time to finish.” When the GC says “Time is of the essence on this project. There’s never an excuse for not getting the job done on time. You’ll be held fully responsible." The ASCC sub can say “We agree to make a good-faith effort to help you meet your completion date, but we can’t give up any delay claim rights if we incur more cost for reasons outside our control." When the GC says “I need your subcontract price to be firm. Neither I nor the Owner want to worry about price increases that are out of our control." The ASCC sub can say “My bid proposal included a price escalation clause. One of the reasons I could give you such a low bid is because I didn’t have to build contingencies into my price." When the GC says “We’re going to get this project done quickly. I don’t expect any delays." The ASCC sub can say “Then the escalation clause really shouldn’t be a factor. We’ll be in and out before we get any surprise price increases." When the GC says “We can always address unexpected price increases later if they arise." The ASCC sub can say “You and I both know that leaving issues like this unresolved can lead to disputes later. Let’s address this now so we can focus our energies on building the best project possible." Reference: https://www.glass.org/sites/default/files/2019-11/Top%2010%20Contract%20Clauses%20-%20TT07.2018.pdf rzuellig Tue, 15 Mar 2022 15:55:00 GMT f1397696-738c-4295-afcd-943feb885714:252 https://ascconline.org/Home/News/articleType/ArticleView/articleId/248/Guidance-for-Concrete-Contractors-4-in-a-Series#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=248 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=248&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/248/Guidance-for-Concrete-Contractors-4-in-a-Series Jim Klinger, concrete construction specialist The Voice Newsletter February 2022 Full disclosure: The human central nervous system is a totally natural product that looks like it could be peeled right out of one’s dearly departed corpse and laminated onto a great big sheet of plywood (just run an image search for “real nervous system” and see what appears). The system is designed to transmit information related to certain loads and stresses. Any learned discussion of this system typically involves use of these terms: tension, compression and even depression. The nervous system obviously works, but the medical profession cannot say they know exactly how. Just when they think they’re getting close, technical advances cause another new feature to appear. It is sometimes possible to control the behavior of the nervous system with chemicals, but it cannot always be guaranteed when the effects might kick in; perhaps within 60 minutes, but anything more than 90 minutes would probably be unacceptable. Some might say any effort to influence or predict the behavior of the nervous system would be a purely trial-and-error proposition. And for years they’ve been telling us that concrete’s the thing that moves in mysterious ways. ____________________________________________________________ Despite advances in its component technology, concrete remains a mostly natural product. Potential compressive strength uncertainties might exist at any time during construction; from the first introduction of mix water to long after supporting formwork has been removed. According to ACI 318-19 Commentary recommendations referenced in Chapter 26, engineering judgement should be applied to help evaluate and determine significance and structural implications once apparent low compressive strength has been suspected. You aren’t likely to find the term “engineering judgement” defined explicitly anywhere in civil engineering textbooks or construction industry literature. Roughly speaking, the term might commonly be used to describe a developmental process that combines classroom education and a healthy dose of field experience to further one’s understanding of the unpredictable behavior of a naturally moving target. Ideally, the field portion of the process that is supposed to refine an engineer’s sense of concrete situational awareness evolves over the course of one’s career. After all, how many engineering textbooks could possibly cover practical, potential concrete strength issues commonly detectable only in the field; often subtle conditions that involve materials, forming, placing, finishing, inspecting and testing? Many veteran engineers and ASCC members will tell you straightaway that impressions of their own jobsite experiences concluded with an understanding that no matter what the textbooks and computer programs say, concrete seems to move in unpredictable--and often mysterious--ways. ____________________________________________________________ In a recent “President’s Memo” column, (Concrete International, January 2022) ACI president Cary Kopczynski introduced a Constructability Certification program aimed at design engineers and currently being developed to “include training modules that will provide designers with a working knowledge of formwork, reinforcing bar detailing, specifying concrete, differences in the way designs should be approached as a function of project delivery type, and many more subjects”. In addition to describing the rationale driving the constructability training modules, Kopczynski reminds us of the importance of collaboration between designers and builders. Collaboration is the key to most successful projects and a fantastic way to help encourage the development of engineering judgement. Unfortunately, some industry legal/contract language can make collaboration either impossible or very cumbersome. In a design-build project, for example, there is a fairly decent chance that an ASCC concrete contractor might actually have a seat at the bar next to the engineer when the Owner pulls the pen out to sketch schematic details on the proverbial cocktail napkin. On the other hand, if a project is set up to be the standard design-bid-build, AIA contract language will probably limit direct communication between the concrete contractor and the engineer, which means communications could be tied up with RFIs and red tape. After all, how many are there among us who have been told by a GC that we are not allowed to collaborate with the engineer directly, that we have to involve the GC first? And how long did that take...and was it ever productive and beneficial to the Owner? To make matters worse, our colleagues at the American Society of Civil Engineers (ASCE) tell us that it is okay for a contractor to collaborate with the engineer during the design phase of a project, just as long as that same contractor is not allowed to bid and build the job: Periodic constructability reviews conducted by the design professional during the project design phase may reduce problems during construction and help control costs. Often, constructors can be solicited during project design to assist with constructability reviews. When soliciting contractors to participate in constructability reviews, it is critical that the contractor not be placed in a position where a conflict of interest could occur. Contractors conducting constructability reviews must not be allowed to bid on the construction project being reviewed. Despite these industry obstacles, however; once a project is awarded, the ASCC concrete contractor should make every effort to follow Kopczynski’s advice. Approach the engineer ...and collaborate. At a minimum, ACI documents provide two possible opportunities to make this happen. ACI 117-10, Section 1.1.3 states that a meeting among the contractors to discuss the work and tolerances is mandatory; the owner and the design team, however, do not have to attend. Invite the structural engineer (and the owner) anyway. If they choose not to attend, insist that both are copied on the meeting minutes. ACI 301-20, section 1.6.1 states that, if specified, the concrete contractor must attend a preconstruction conference with the engineer to discuss project requirements, acceptance criteria, and responsibilities. So meet with the engineer. Come to the meeting prepared. Tell the engineer you are an ASCC concrete contractor and you want to collaborate on a successful project. The key here is that the concept of collaboration between the structural engineer and the concrete contractor is way too understated in many ACI documents. It can be sensed in so many places, just below the surface. Thanks to Cary Kopczynski for helping to bring this to light. ____________________________________________________________ Speaking of unpredictable behavior and judgement, two members of the ASCC Technical Division assisted in publishing “Expect Compressive Strength Test Results Less Than Specified Strength on Every Project” in a recent industry magazine (Concrete International, February 2022). Additional technical writing assistance was provided by Colin Lobo (NRMCA) and Eamonn Connolly (McHugh). In this article, strength testing of concrete cylinders is explored, along with reserve cylinders, core testing and engineering judgement. It’s not what you think. rzuellig Tue, 15 Feb 2022 16:21:00 GMT f1397696-738c-4295-afcd-943feb885714:248 https://ascconline.org/Home/News/articleType/ArticleView/articleId/245/Upside-down-Stud-Rails#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=245 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=245&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/245/Upside-down-Stud-Rails Jim Klinger, concrete construction specialist The Voice Newsletter January 2022 Imagine, if you will, the following scenario.  You are scheduled to start installing rebar and PT for an elevated concrete slab tomorrow.  The plywood deck has been swept clean, and the MEP crew has moved out of your way.  You get a call from your stud rail (also known as PSR, or punching shear resistor) supplier, who informs you that supply chain issues are preventing him from delivering the product to your jobsite on time.  Or... Imagine, if you will, the following scenario.  You have scheduled a 500-plus CY placement for the day after tomorrow.  The rebar and PT has been completed and is awaiting inspection.  You get a call over the radio from your field foreman that your crew has forgotten to install the stud rails required at just about every column on the floor. In both cases, all may not be lost, and the placements might not have to be cancelled.  As it turns out, the “stud” part of the stud rail is needed to prevent the slab cracking that typically occurs during a punching shear failure.  The stud itself does not care if it is right-side up or up-side down.  The “rail” part of the stud rail is merely a convenient means of spacing the studs.  In other words, it is entirely acceptable for the stud rails to be installed after the rebar and PT have been installed, just as long as the spacing and placement tolerances are kept within the bounds indicated on the construction documents. Reference:  Concrete Q&A, ACI Concrete International, January 2022 rzuellig Sat, 15 Jan 2022 20:11:00 GMT f1397696-738c-4295-afcd-943feb885714:245 https://ascconline.org/Home/News/articleType/ArticleView/articleId/244/Estimating-for-Concrete-Contractors-3-in-a-series#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=244 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=244&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/244/Estimating-for-Concrete-Contractors-3-in-a-series Jim Klinger, concrete construction specialist The Voice Newsletter January 2022 Full disclosure:  To oversimplify enormously, philosopher Blaise Pascal approached the issue of whether or not there was a deity by saying that, if we took a leap of faith and assumed there was, and we were wrong, then we would lose nothing but a few hours of wasted prayer and adoration.  If we were right, then we would win heaven. If we assumed there was no deity, and we were right, we have neither lost nor gained anything; but if we were wrong, we have lost our eternal souls. Therefore, Pascal suggested, the only logical and intelligent course of action is to assume there is a deity. From this bit of narrow reasoning came the concept of “Pascal’s Bet”, which refers to acting as though something exists…however slim the odds…when its failure to exist will not harm you, but its existence could affect you greatly In the last two episodes of the ASCC VOICE, the Technical Division offered suggested ways to mitigate unsavory financial problems that can usually be prevented by a few careful keystrokes applied whilst preparing a bid proposal.  In this episode, we present typical terminology used by veteran concrete estimators. Some of it may seem a bit colorful, but we are all adults here. Estimate Level Description Plus Tolerance Minus Tolerance 1 "Cocktail Napkin" 50% 30% 2 Schematic 30% 15% 3 Design Development 20% 10% 4 75% CD 15% 5% 5 90% CD 5% 5% 6 Bid Day perfect perfect 7 Post-bid options n/a n/a   Estimate Levels:  The table above has been morphed from several construction and process industry sources over the years; mostly from ASTM E2616-11, “Standard Classification for Cost Estimate Classification System”.   Estimate levels range from Level 1 (“cocktail napkin”) to Level 7, which only kicks in after project award-when pricing needs to be prepared for alternates and last-minute add-ons.  The plus and minus tolerances are loosely based on ASTM E2616, with the exception of Levels 6 and 7.  Our thinking is that the estimate better be dead-nuts perfect at Level 6, and at Level 7 anyone could see plain as day that your price is right on the money. ROM Estimate:  Rough Order of Magnitude, numbers prepared by others. ROM Estimate:  Refined Order of Magnitude, numbers prepared by you. SWAG Number:  Scientific, wild-assed guess.  Google it. PIDOOMA Estimate: Pulled it directly out of my ass estimate.  Google it. Ballpark Estimate: A number no worse than most, but probably better than some. Should Cost Estimate:  See SWAG number, above. Greenfield Estimate: Price based on pristine, untouched land.  Just a green field. Brownfield Estimate:  Land has prior issues, possibly contaminated. Upset Fee: Any higher than this and the owner will be upset. Scary Low Estimate:  Your price is Pascal’s Bet writ large…and lost. rzuellig Sat, 15 Jan 2022 20:10:00 GMT f1397696-738c-4295-afcd-943feb885714:244 https://ascconline.org/Home/News/articleType/ArticleView/articleId/241/Estimating-for-Concrete-Contractors-2-in-a-series#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=241 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=241&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/241/Estimating-for-Concrete-Contractors-2-in-a-series Jim Klinger, concrete construction specialist The Voice Newsletter December 2021 Full disclosure: It’s 17 July 1982, just about first light. I’m beachcombing barefoot along the pristine Ocean City shoreline. Up ahead, I spot a lone surfcaster working the incoming tide. Several species of highly prized sport fish are running along the Jersey coast now, and I can see straightaway this guy has hooked into one of them. The angler finesses the fish in past the first breaker and then through the surging pull of ocean backwash and drags it safe to dry sand. It’s a striper, a real beauty. By and by, we exchange pleasantries and get to talking. As it turns out, he’s an engineer who retired just yesterday after a career based in the Philadelphia construction market. I tell him my first engineering classes get underway in a few weeks at university and ask if he has any words of advice for a young guy just starting out. “That’s easy”, he says, “never fool yourself into thinking that you know it all in the concrete business, even up to the day you retire”. Looking back on it after all these years…boy, was he right. Despite tremendous pressures brought to bear on the concrete construction industry by the pandemic, the ASCC Technical Division staff nearly doubled in size in 2021. Over the past year, this staff fielded several hundred concrete construction issues submitted by contractors taking advantage of the ASCC Hotline and Email Forum. And, true to the fisherman’s advice recounted above, we managed to learn something new with almost every issue or inquiry. Our jobs have been made much easier thanks to generous member participation in ASCC Technical Committee and Constructability Committee meetings and related activities. We are a non-profit organization that thrives on members helping each other navigate the concrete construction business, and it is especially bragworthy to see competitors leave their helmets and party affiliations at the door and lend a hand to fellow members. Last month, we presented sample bid “inclusion and exclusion” proposal line items that could help minimize risk in an upcoming project. For this issue, we spent several hours sifting through past Hotline and Forum issues in an attempt to flush out examples that featured conflict and financial exposure that might very easily have been mitigated at bid time by using another valuable concrete estimating tool: contract scope allowances. As it turns out, there were several such issues that jumped out. No one up and down the project food chain wants to get blindsided with late or seemingly unsubstantiated requests for cash money in the form of backcharges or proposed change orders. Nasty surprises - even if they are valid - can be some of the quickest ways to wreck a perfectly fine business deal. As concrete contractors, the best we can do to avoid unsavory conflict is to alert the owner of potential extra cost items up front at bid time, with suggested allowances (also sometimes called contingency or reserve sums). ( N.B.: Industry Standard ASTM E2168-10(16) is titled Standard Classification for Allowance, Contingency and Reserve Sums in Building Construction Estimating. The significance of the three commonly used estimating terms (e.g. allowance, contingency, reserve) is described in Section 4.1 as follows: “When preparing construction, project, and program cost estimates, it is often necessary to make monetary provisions for change or risk, or both, or other exigencies where information is incomplete)." In some cases, project allowances may have been anticipated by the owner and the design team, typically appearing in MasterFormat Division 1 “Section 01 21 00: Allowances” or similar. In most of the specifications we reviewed, the projects were large public works-type, and allowances were only specified for work scopes related to Division 6 and higher; structural concrete wasn’t even mentioned. This is why it is so important for the concrete contractor to exercise due diligence, scour the construction documents, and rely on past experience for guidance when preparing each bid. Classic scope allowance items that typically carry risk of financial exposure to the unwary concrete contractor are as follows: Crack repairs not clearly quantified at bid time Grinding, filling of floors to suit follow-on trades Lean concrete foundation backfill to replace unsuitable soils Concrete needed to compensate for metal deck deflection Concrete needed to compensate for misplaced subgrade Concrete needed to compensate for misplaced shoring Ice in concrete readymix due to weather Incidental and/or accidental trade damage done to our work by others Incidental and/or accidental trade damage done by our crews. Rework required at architectural concrete mockups Testing/inspection costs (e.g. early breaks, etc.) for PT, stripping, and so on Repairs due to follow-on damage caused by deicing chemicals Costs associated with breaks in the supply chain Costs associated with COVID Time-related maintenance/repair issues, PT movement, Curling, Deflections We have seen cases this year where the customer just plain didn’t know that elevated concrete slabs typically deflect after we remove the shoring, that PT structural concrete might move over time, and that reinforced concrete parking structures really do require owner maintenance budget attention over the life of the structure. There are some savvy structural engineers who include a section in their General Notes titled “Special Notes to Owner,” or similar statements meant to alert all stakeholders that unquantifiable costs are likely to be incurred, presumably handled through owner allowance budget line items. But there are other cases when it behooves the concrete contractor to raise allowance red flags early, either via pre-bid RFIs or carefully crafted proposal language. In Part #3, we will consider certain interesting and amusing concrete estimating terminology, such as “Should Costing”, “Upset Fee”, “SWAG numbers” and “PIDOOMA budgets”. rzuellig Wed, 15 Dec 2021 16:39:00 GMT f1397696-738c-4295-afcd-943feb885714:241 https://ascconline.org/Home/News/articleType/ArticleView/articleId/236/Estimating-for-Concrete-Contractors-1-in-a-Series#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=236 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=236&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/236/Estimating-for-Concrete-Contractors-1-in-a-Series Jim Klinger, concrete construction specialist The Voice Newsletter November 2021 Full disclosure: A pat on the back and a tip of the hat to Vince Bailey, who writes the “Estimators Edge” column that appears in the monthly AWCI (Association of the Wall and Ceiling Industry) publication “Construction Dimensions”. In addition to offering estimating guidance, Bailey’s columns typically chronicle the various afflictions that can plague intrepid drywall “bidmeisters” who strive to forecast the future cost of work whilst relentlessly subjected to diamond-crushing upper management, industry, and now supply-chain pressures applied from every possible direction. Bailey’s wry sense of humor and sidelong glances at the life of a fellow construction industry estimator/project manager are greatly appreciated and widely circulated here among the ASCC Technical Division staff. Assume for a moment that you are a concrete construction estimator. Like any competent, professional “bidmeister” your work product has been diligently prepared in accordance with the two main industry standards that govern your trade, namely ASTM E2516-11 “Standard Classification for Cost Estimate Classification System” and ASTM E2168-10 (16) “Standard Classification for Allowance, Contingency, and Reserve Sums in Building Construction Estimating”. You have scoured, devoured, and completely understand all the construction bid documents, completed your quantity survey, reviewed a preliminary project schedule, and priced the concrete scope according to your customary, proprietary format. Next…the real work begins…crafting the actual bid proposal package in the limited time available. To prepare for this task, you have reviewed the relevant sections of ACI 301-20 and ACI 117-10; since those specifications can easily be (and often are) incorporated into concrete construction contracts with one simple sentence. More importantly, you have re-examined the priceless advice contained within the 44 ASCC Position Statements; crucial documents that are renowned for preventing red ink from infecting a concrete contractor’s monthly job cost reports. Armed with this information, you fill out the bid form, write the price proposal letter, and send it off to the customer with not a minute to spare…hoping all of the bases were covered. However… Almost any veteran ASCC member will tell you that incomplete preparation of bid proposal qualifications (in other words inclusions, exclusions, assumptions, carve-outs and other strategic adjustments to weasel words in the construction documents) can undermine even the most precisely assembled estimate. There is nothing worse than walking away from a jobsite meeting after it has been demonstrated (usually in annoying fashion by others) that you are now the proud owner of a costly, unfunded scope of work due to an inadvertent error or omission in your own proposal language. Here at the ASCC Technical Division we sometimes handle cases where fellow concrete contractors find themselves in an unfortunate financial situation related to insufficient proposal language. During the past year, we have been assembling a collection of sample bid proposals prepared by ASCC colleagues that contain examples of qualification language intended to avoid costly and unnecessary contractual booby-traps. Over the course of the next few months, we will share with you the best examples we have found that could be considered for possible inclusion in almost any concrete construction proposal. This month, we present typical exclusion and assumption items, limited to 25 of each flavor due to limited space. Of course, like with anything else, each line item must be considered on a case-by-case basis. N.B.: One of the most beneficial features of our humble non-profit organization is that ASCC members actively and generously help other members to be the best concrete contractors we can be. In that respect, ASCC is wildly successful. With that in mind, your Technical Division would appreciate it if any members wish to share with us example bid proposals or other documents you have used to defuse booby-traps and/or time bombs that might be lurking somewhere in a contract due to an inadvertent error or omission. All such documents will be kept anonymous and confidential. Bid Proposal Qualifications: Sample Exclusion Items 1.    All costs associated with crack repairs of any kind. 2.    All costs associated with any concrete testing and inspection. 3.    All costs associated with test cylinder curing boxes, handling of cylinders. 4.    All costs associated with concrete testing shown in IBC Table 1705.3. 5.    Supply of anchor bolts, embed plates, misc. metals to be set in concrete. 6.    Survey control. Assume provided by others twice at each floor level. 7.    All costs associated with toilet facilities, dumpsters, parking, temporary electric power. 8.    All costs associated with testing for flatness, levelness, F-numbers. 9.    Clean up of trash and debris generated by others. 10.    Site dewatering, geotechnical dewatering, nuisance dewatering, rainwater removal. 11.    MEP coordination drawings, MEP penetration coordination, MEP coordination meetings, MEP BIM meetings, MEP coordination virtual meetings. 12.    MEP or other trade penetrations not clearly dimensioned on structural drawings. 13.    Lime treatment, lean concrete, soil backfill or other unsuitable soil remediation. 14.    All work outside the main building footprint. 15.    Fall protection, safety covers over penetrations at metal decks. 16.    Fall protection at elevated formed slabs after shoring has been stripped. 17.    Welding of reinforcing steel, couplers not shown on structural drawings. 18.    Surveys, as-builts of metal decks and supporting substrate. 19.    Demolition, hazardous material remediation, rock excavation. 20.    Curbs not shown on architectural or structural drawings. 21.    Edge forms, pour stops, blockouts at metal deck slabs. 22.    Shoring of metal decks, extra concrete due to deck deflection on pour day. 23.    Clean-up of all concrete leakage through vented or unvented metal decks. 24.    All costs associated with post-installed anchors, drilled-in anchors. 25.    Winterization of jobsite access ways, vehicle tire wash stations. Bid Proposal Qualifications: Sample Assumption Items 1.    Building pad is prepared to include all elevation changes, slopes and contours within plus or minus 1/10 foot from design subgrade. Pad grading to be professionally certified prior to turnover. 2.    All floors are surveyed by others for top of slab finish quality. Test reports to be transmitted to us within 72 hours of concrete placement. 3.    Assume normal work hours, 8-hour days, Monday through Friday. No OT or holidays. 4.    Assume all embedded items are furnished by others, complete with approved setting drawings and templates for each column location consistent with the level of setting tolerance accuracy expected. Templates to be 1/8 inch steel, minimum. 5.    Assume progress payments shall be made on a monthly basis and will be payable 30 days from submission of monthly progress billing. This proposal does not recognize nor agree to any “pay when paid” terms. 6.    Assume safe access to metal decks is furnished and maintained by others. 7.    Assume all access to the work (e.g. permits, street closures, encroachments, concrete pump/readymix truck access, removal of power lines, etc.) is provided in a timely manner by others. 8.    Assume we cooperate with the test agency regarding concrete sampling. We assume all curing boxes, temporary water and electrical power, protection (sheds) and all cylinder handling and initial curing is by others. We assume we have no links in the test specimen chain of custody. 9.    We assume we own “protection” of the work until the end of the curing period defined by and consistent with ACI 301. 10.    We assume the Owner is carrying an allowance for crack repairs, if needed. 11.    We assume the Owner is carrying an allowance for floor grinding or floor filling (e.g. Ardex or similar) to make slabs compatible with follow-on flooring. 12.    We assume readymix batch-to-placement time is 120 minutes, not 90 minutes. 13.    We assume our scope is structural concrete only as shown in the architectural and structural drawings. We assume any and all concrete shown on MEP, Civil, Site, Landscape, etc. drawings is furnished and installed by others. 14.    We assume our wall and column forms can be removed next day after placement. 15.    We assume our approved shop drawings constitute adequate “as-builts”. We assume posting of project RFIs, bulletins, etc. is to be by others. 16.    We assume adequate space for our trailer and supporting Conex box is provided by others, along with electrical power. 17.    We assume adequate temporary task lighting is provided and maintained below formed and stripped floors by others. 18.    We assume all-weather access to the work is provided by others. 19.    We assume all trade coordination is by others. 20.    We assume all furnish and install of sleeves, boxes, inserts, etc. required by other trades is by others. 21.    We assume adequate electrical power for small tools and vibrators is provided at each framed and finished floor level within mutually agreed upon distance from the work. 22.    We assume we get the opportunity to review steel embed and baseplate shop drawings for bolt hole sizes, nailer holes, grout vent provisions, etc. prior to fabrication. 23.    We assume all curing is by spray-on curing compound only. We are carrying no extra cost for wet-cure nor extra time on the schedule for wet-cure. 24.    We assume shoring and lagging is placed 2 inches maximum “out” and zero inches “in”. All shoring and lagging as-built surveys are to be by others. 25.    We assume all exposed nails, staples, etc. placed by other trades are removed and patched from slab and beam soffits by others. rzuellig Mon, 15 Nov 2021 17:01:00 GMT f1397696-738c-4295-afcd-943feb885714:236 https://ascconline.org/Home/News/articleType/ArticleView/articleId/233/Technical-Notes-from-the-3-Dot-Lounge#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=233 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=233&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/233/Technical-Notes-from-the-3-Dot-Lounge Jim Klinger, concrete construction specialist, The Voice Newsletter October 2021 Note #1: The ASCC Technical Division welcomes member phone calls to our Hotline and email traffic submitted by members either through the Forum or directly to us. Already this year we have fielded several hundred requests from our members for assistance with technical issues ranging from apparent cold joints in the middle of a mat pour to suggested work-arounds for metal deck shortages and similar supply-chain sourcing issues. In most cases, the calls or emails involve time-dependent concrete construction issues needing to be addressed in a timely manner. In order to provide the most efficient service, consider including the following information with your initial email request. For Hotline calls, companion emails containing relevant backup information can be very helpful as well… State the problem in as much detail as possible… Send copies of the construction documents, including relevant plans, specifications, mix designs. Use Dropbox or similar for large file sizes... Whenever possible, include photographs or videos… Consider sending us your proposal letter and your contractual scope of work to help us understand what work product you owe the project… Send copies of field, inspection and test reports prepared either in-house or by others. Send copies of relevant project correspondence… For issues related to cracking, send photographs and crack field maps, preferably marked up on structural plans that indicate design location of control joints… Send copies of non-compliance reports… For performance-related problems (e.g. cracking, curling, delamination, scaling, excessive deflection, etc.) explain when the issue was first detected relative to time of initial concrete placement… For mix designs, include supporting strength data and shrinkage data… If all else fails, do not hesitate to pick up the phone and call the ASCC Hotline… Note #2: The ASCC Technical Division needs some help as well... We need clear photographs of reinforcing steel congestion in walls, slabs, beams and columns that are really beyond the pale. Conflicts with PT tendons are a plus… We are looking for example details where the licensed design professional actually made provisions in the structural drawings for vibrator access through congested reinforcing steel in walls, slabs, beams, etc... We are looking for examples where the licensed design professional assigned a tolerance to the portion of column anchor bolts embedded in a pile cap, footing or mat slab. Such a tolerance would be shown relative to top of concrete and the end of the anchor bolt... As a concrete contractor, have you ever been asked to become involved in a project to provide constructability service or counsel to an owner or licensed design professional related to concrete construction or logistics at the early schematic phase of a project? If you have, we would appreciate hearing about your experience… At the start of a concrete construction project, how do you typically handle the provision and maintenance of jobsite curing facilities to be used by the testing agency for the lab- cured acceptance cylinders? In many cases, such items as water and temporary electrical power are assigned to the general contractor. If the testing agency has requirements not known at the time of your bid, how do you craft your bid proposal? Do you ever get saddled with transporting or handling test cylinders, say moving them from an upper floor level to the ground? Do you typically provide a jobsite cylinder storage box? Do the testing agency reports include data indicating cylinder temperature for the first 24 hours after casting? Let us know… Are any of your projects using temperature-match curing? If they are, please let us know how the cylinders are handled, stored and transported during the first 24 hours after molding… Note #3: Thanks to all of the ASCC members who attended our September Annual Conference and participated in the Technical Committee meetings and roundtables. This was my first conference, and it became instantly (and painfully) obvious to me that our membership is just full of wonderfully talented characters. Thanks to all of the folks who stopped me in the hallway or at meetings to introduce themselves and say hello… Note #4: Thanks to all of the ASCC members who had anything at all to do with the event preparation and behind-the-scenes work…in particular any of the glass, antique wood and chain- link fence specialists that may have been assisting the Safety Awards committee… Note #5: Here’s a bit of old-school investment advice. Purchase a 3-ring binder and print paper copies of ACI 301-20, ACI 117-10 and the current copies of the 44 ASCC Position Statements. At first glance, there is a lot of material in there. But in most cases, this is material that describes scope items that you contractually owe to a project. In other words, you either need to know the material outright or at least be able to find the information quickly. All it takes is thumbing through the pages for about an hour or so each week just to stay familiar with the binder contents… rzuellig Fri, 15 Oct 2021 18:55:00 GMT f1397696-738c-4295-afcd-943feb885714:233 https://ascconline.org/Home/News/articleType/ArticleView/articleId/213/What-Brings-You-to-the-ASCC-Hotline#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=213 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=213&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/213/What-Brings-You-to-the-ASCC-Hotline Jim Klinger, The Voice Newsletter September 2021 The ASCC Hotline has been in existence for about 50 years, taking calls on business, contracts/specifications and technical issues. The success of the Hotline is not about the person answering the calls, but the contractors that call in. As contractors call, more information is obtained about an issue or project, which collectively leads to a pinpoint answer, a stronger strategy, an ASCC Position Statement, or an ACI article. While the issue or solution is shared with other contractors, the caller is always anonymous. The subjects of Hotline calls vary as shown below, but callers typically receive information that reduces their cost or schedule. Remember to use the ASCC Concrete Construction Hotline (800) 331-0668 or email ascchotline@ascconline.org or call (925) 234-2623 or email jklinger@ascconline.org. Business • Bidding • Estimating • Finding Suppliers, Subcontractors or Consultants • Change Orders • RFIs • Warranties • Legal Advice • Readymix • Inspection Checklists Contracts and Specifications • Contract Clauses • Subcontracting • Scope of Work/Proposal Letters • Contract Exclusions/Allowances • Preconstruction Conferences • AIA and ACI Specifications • CSI Specification Standards • ASTM Standards • ICRI Requirements Technical • Cracks, Spalls, Popouts, Blisters, Delamination, Crazing • Cold and Hot Weather Concreting • Curing Requirements and Methods • Concrete Pumping • Placing and Finishing • Repair, Including Removal and Replacement Issues • Construction Tolerances • Field and Laboratory Testing Standards and Procedures • Inspection Issues • Destructive and Nondestructive Tests • Quality Control and Quality Assurance • Formwork and Formwork Design • Reinforcement and Post-Tensioning • Normalweight and Lightweight Concrete Mix Designs • Mass Concrete Requirements and Methods (Fly Ash, Slag, etc.) • ACI Building Code Requirements • ACI Document Interpretation rzuellig Wed, 01 Sep 2021 18:29:00 GMT f1397696-738c-4295-afcd-943feb885714:213 https://ascconline.org/Home/News/articleType/ArticleView/articleId/125/Concrete-By-Any-Other-Name#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=125 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=125&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/125/Concrete-By-Any-Other-Name Jim Klinger, Concrete Construction Specialist, The Voice Newsletter July/August 2021 Call it coincidence. I had a chance to commiserate with an old construction colleague over this past holiday weekend. Both of us had set foot on our first concrete construction jobsite during the second week of July, 1979 at the same small, mid-rise apartment project  just outside Bethesda, Md. Any ASCC member will tell you that one’s first day on an active concrete construction site features mysterious aromas that can be terribly intoxicating and addictive. And so it was with us. One whiff of concrete construction work and we were both hooked. (N.B.: Some say that the concrete business gets into your blood through the nose; that some time during your first day on the job an airborne VOC molecule plume emanating from form oil, freshly-stripped lumber and curing compound joins forces with the aroma of warm, hydrating concrete and find their way into your nasal receptor neurons and take up residence. This somehow becomes a permanent part of your instinctive olfactory system that sure enough kicks in every time you get within half a block from any concrete construction jobsite). Over the decade that followed we worked on many concrete construction projects in the Washington, D.C. area. Sometimes we were assigned to the same project, sometimes not. We parted ways for good in 1990, when I moved to California. Now here it is 42 years later, and we both find ourselves recuperating from recent injuries. His was a bout with COVID-19; not severe enough to be hospitalized, but bad enough to be confined to quarters for several weeks. We talked as old men do, reflecting on shared history and evaluating various concrete construction issues of the day. We reminisced about that one job in downtown D.C. when our crew couldn’t get much done due to ongoing demolition of a large concrete structure on an adjacent block. Distraction soon turned into fascination, and at quitting time we became instant sidewalk superintendents-along with many others-who were transfixed at the spectacle of a crawler crane swinging a 3000 lb. wrecking ball about, relentlessly beating the holy sweet bejeezus out of that stalwart reinforced concrete frame and not making much headway with each impact of the steel ball. We marveled at the strength of that old structure and straightaway gained an understanding of the tremendous forces it would take to cause the reinforced concrete frames we were currently building to collapse. Looking back on it, witnessing a reinforced concrete frame being torn apart is a fantastic teachable moment; and we now understand why every aspiring doctor in medical school must first take a human body apart in Gross Anatomy 101. I asked my old colleague if he had seen any of the recent news reports covering the collapse of a reinforced concrete building. “It reminds me of expat contract work in certain Middle East countries. I didn’t notice a lot of bars there,” he said. Finally I asked him if the COVID had given him a case of anosmia, a widely-reported side effect of the virus. “Not a chance”, he said. “I walked by a concrete construction jobsite just last week. That smell was music to my ears.” __________________________________________________________ Check Your Bookshelves… Below are short reviews of two publications that are strongly recommended to be a part of your daily working documents. In one case, ACI 301-20, you may already be contractually obligated to meet its specified requirements by simple reference in construction documents. Once you obtain the current version of 301, holding on to previous versions is highly recommended. ACI 301-20: Specifications for Concrete Construction. This is perhaps the single most valuable ACI reference document available to an ASCC concrete contractor. Its importance can be measured along several fronts. The most current version is hot off the press, just released last year. The ACI 301 specification was first drafted in the early 1930’s and is still evolving. It was always intended to be easily incorporated into project construction documents by specifiers via simple reference. The most current version was issued last year with the following introduction and description: This is a Reference Specification that the Architect/Engineer can apply to projects involving concrete construction by citing it in the Project Specification. A mandatory requirements checklist and an optional requirements checklist are provided to assist the Architect/Engineer in supplementing the provisions of this Specification as required or needed by designating or specifying individual project requirements. The first five sections of this Specification cover general requirements for concrete construction. These sections cover materials and proportioning of concrete; reinforcement and prestressing steel; production, placing, finishing, and curing of concrete; formwork performance criteria and construction; treatment of joints; embedded items; repair of surface defects; and finishing of formed and unformed surfaces. Provisions governing testing, evaluation, and acceptance of concrete as well as acceptance of the structures are included. The remaining sections are devoted to architectural concrete, lightweight concrete, mass concrete, post-tensioned concrete, shrinkage-compensating concrete for interior slabs, industrial floor slabs, tilt-up construction, precast structural concrete, and precast architectural concrete. Once the reader has a working knowledge of ACI 301-20, the specification becomes a comprehensive guide to almost every facet of concrete construction you are likely to encounter. This is not a quick, easy read. The best way to gain a working knowledge is to digest the contents section by section. In many cases, this document will be routinely consulted over the course of a concrete construction project; any time spent getting familiar with the contents is sure to pay off. Tolerances for Cast-in-Place Concrete Buildings- A Guide for Specifiers, Contractors, and Inspectors. This was written by Bruce Suprenant and Ward Malisch and published by ASCC in 2009. The original publication was in softcover book format with 143 spiral-bound pages. Unfortunately, the hard copy publication is now out of print. A pdf version is available at the ASCC Bookstore. This document is a tour-de-force classic that belongs on every concrete contractor’s bookshelf. ACI 117-10 (Specification for Tolerances for Concrete Construction and Materials) and the companion ACI 117.1R-14 (Guide for Tolerance Compatibility in Concrete Construction) are the most current ACI resource documents that address tolerances for structural concrete work and are the most likely to be referenced in construction specifications. But sometimes the information contained in the ACI documents isn’t enough to help explain a perceived tolerance issue that arises during a high-pressure construction project to a customer that has been wired to view concrete work with zero-defect baseline expectations. This is where the ASCC Tolerances Guide can be consulted. In discussions with other colleagues who have a working knowledge of the Guide, we all agree that one doesn’t have to read very far into the first few chapters to realize the tremendous amount of research that had to have happened behind the scenes to make it possible. For each tolerance category (e.g. horizontal, vertical, etc.), the authors traced its history, rationale, and any available as-built supporting data. Then, most importantly, the authors suggest tolerances that are reasonable, achievable and economical for consideration by an audience consisting of concrete contractors, designers and owners. Similar to ACI 301, a portion of the Guide was always intended to be be incorporated directly into project construction documents by a specifier via a simple two-sentence reference clause. Any concrete contractor who has had to argue their case to a GC or owner’s rep will tell you that it always helps to know the history behind a tolerance and what reasonable, achievable and economical tolerances should be. The ASCC Guide provides that background. Similar to ACI-301, any time spent reading the ASCC Tolerances Guide is bound to pay off. rzuellig Sun, 01 Aug 2021 16:00:00 GMT f1397696-738c-4295-afcd-943feb885714:125 https://ascconline.org/Home/News/articleType/ArticleView/articleId/124/A-Quick-Saturday-Spin-of-Biblical-Proportions-or-Why-We-Dont-Allow-the-Technical-Department-to-Answer-the-Safety-Hotline#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=124 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=124&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/124/A-Quick-Saturday-Spin-of-Biblical-Proportions-or-Why-We-Dont-Allow-the-Technical-Department-to-Answer-the-Safety-Hotline Jim Klinger, Concrete Construction Specialist, The Voice Newsletter June 2021 About a month ago I purchased one of those so-called “Ebikes” from our local big-box store. This particular model features 14-inch wheels and fold-down handlebars. A rechargeable battery-powered motor can be used to supplement the traditional foot pedals. Gears, shock absorbers and a comfortable seat were not available options on this model. The purchase was motivated by domestic pressure provoked by post-retirement weight gain to the tune of about 50 pounds above normal. The general idea was to ride the Ebike, using the foot pedals, up and down the neighborhood streets. The electric motor assist would only be used sparingly. My last bike ride was on a banana-seat Stingray down the side streets of Tucson in 1966. The raised handlebars made popping wheelies a breeze. Although some 55 years have passed, I still remember cruising on the easily-controlled Stingray along gently rolling, off-road desert trails for hours on end. It took a few days to get used to the Ebike’s controls. I found the steering and handling to be quite difficult. This was definitely not the classic 1966 Stingray. On a Saturday morning, I was elected to drive my wife to the local grocery. After opening the garage door, I figured I could make a quick Ebike run to the local park and back before the wife finished her morning constitutional and nobody would be the wiser. The electric motor could be brought to bear if needed. The sleepy neighborhood streets were quiet, so off I went for a quick spin. I was not wearing a helmet, nor did I even consider it. What happened next hangs in my memory in a vivid, slow-motion blur. I can remember trying out the electric motor, misjudging the turn radius into the park, and losing control of the Ebike when the wheels crossed the transition between asphalt street, concrete gutter and trench drain. I remember sailing face-first into a chain-link fence, and coming to rest in a tangled mess at the base of the fence. Once the wheels stopped turning, I knew I was bleeding and could not feel anything below my waist and only part of each arm. One of the neighbors witnessed the spectacle, called 911, and made sure I did not move. Once the ambulance arrived, the medics boarded me up for a 40-minute ride to the closest local hospital with trauma facilities. I spent the next six days in the ICU. The first night was sleepless, despite being heavily medicated. It was bad enough being paralyzed from the waist down. But the sounds coming from the adjacent rooms in the trauma center were enough to fuel any dreams with a touch of terror. My family was devastated. By the second day, and after many MRI and CT scans, I was diagnosed with a spinal cord injury (SCI), aggravated by an age-related indignity of spinal arthritis. But I also started to regain feeling in my hands, toes and legs. After a few more days, I felt like I might even be able to get out of bed. By the eighth day, I was able to walk, and convinced the doctors to let me go home to convalesce. Prior to release, I received several complimentary fashion items, including mandatory neck braces (one for casual wear, the other for use in the shower). I also received a few days’ supply of catheters, which are self-inflicted tubes that are used to manually drain one’s water plug every six hours or so. As it turns out, SCI injuries can negatively affect the manly hydraulic system. I have since regained full control of those particular bodily functions. As of today, I cannot feel the tips of my toes, but I can walk. My right arm has numb spots, but I can make a fist and write with a pencil. My left arm has a few numb spots as well, but the nerves in my wrist and hand alternate between burning pain and sharp electrical shock. It feels like the bone marrow itches, but any attempt to scratch is extremely painful. Today I am a very humble man. I may not regain 100 percent of my health, but it’ll be close. It could have been a lot worse. I have attended many presentations given by Bruce Suprenant. Bruce typically starts out by telling the audience that one of the best ways to learn something is via mistakes, hopefully mistakes made by others. I am telling you this so you can learn from my mistakes. I can’t say whether or not you should be driving one of these Ebikes. But you really need to wear a helmet (it’s the law in California), make sure to read the safety literature from the manufacturer, and take any training that might be required. It has been said that certain things are “just like riding a bike”. Whether or not that always applies is borderline questionable. It finally dawned on me (after having my face dragged along a chain-link fence) that the ASCC stresses safety in everything we do. Even at the ASCC Technical Committee meetings, the very first item on our agenda is always safety. In the ACI/ASCC “Contractor’s Guide to Quality Concrete Construction” the very first chapter is devoted to safety. The key takeaway here is that safety is a 24-7 concern that applies equally to the jobsite and to quick spins at home on a Saturday morning. And speaking of specifications…when you get laid up in the hospital, it gives you time to prepare a presentation for a World of Concrete luncheon regarding the many difficulties that surround project specifications. In a 1981 edition of Concrete International, Raymond Huen explored specifications and how they might be improved. Huen points out that the first known written specification can be found in the Book of Genesis, Chapter 6. In Chapter 6, the Owner does, in fact, direct the contractor to build a boat out of wood approximately 450 feet long by 75 feet wide. But there had to have been a verbal concrete specification issued by the Owner to the contractor beforehand saying: “You must place an 8-inch thick concrete working slab 500 feet long and 100 feet wide for use by the follow-on boat builder. Do not worry about slope to drain or birdbaths. Those parts can be discussed later”. In similar fashion, Henry Reid’s classic 1877 textbook titled “The Science and Art of the Manufacture of Portland Cement” contains a running commentary of a beef that Reid had with another researcher, John Grant, regarding who first invented a tension test mold. In a fit of pedantic silliness, one of the participants claimed his ancestors were part of the crew on Noah’s ark. “That’s nothing”, said the other, “back then, my ancestors had their own boat”. Stay safe, everybody. rzuellig Tue, 01 Jun 2021 15:59:00 GMT f1397696-738c-4295-afcd-943feb885714:124 https://ascconline.org/Home/News/articleType/ArticleView/articleId/44/Getting-the-Record-Straight-on-Substrate#Comments 0 https://ascconline.org/DesktopModules/CM.NewsArticles/RssComments.aspx?TabID=190&ModuleID=463&ArticleID=44 https://ascconline.org:443/DesktopModules/CM.NewsArticles/Tracking/Trackback.aspx?ArticleID=44&PortalID=3&TabID=190 https://ascconline.org/Home/News/articleType/ArticleView/articleId/44/Getting-the-Record-Straight-on-Substrate Jim Klinger, Concrete Construction Specialist, The Voice Newsletter, May 2021 Here at your ASCC Technical Division, much of our work product is created in response to concrete construction substrate acceptance issues disclosed by members via hotline calls or prompted by Email Forum posts. Sometimes, for example, a concrete floor slab substrate has been deemed unacceptable by a follow-on subcontractor; a flooring installer perhaps. (Whether or not that decision has been rendered to the member in a timely manner might turn out to be a borderline questionable proposition). At other times, a member might request an interpretation- a second opinion- of ambiguous construction document provisions before submitting a bid. This consultation is requested so the member’s bid can be crafted to anticipate and then meet the owner’s substrate expectations at a mutually agreeable price. And sometimes the member’s substrate dilemma is totally self-inflicted. In these cases, we attempt to develop a sensible substrate repair plan or even help draft a request for the owner to accept the as-built; arguing that the member’s installation is in a fit-for-purpose, acceptable condition. The scenarios described above primarily involve acceptance of our completed substrate work by others. On the other hand, at least once on every project, we-- the concrete contractor-- are placed in the position of having to accept a substrate that has either been installed or prepared by others before our work can begin. Based on experience, it’s fair to say that many difficulties surround the mechanics of accepting substrate installed by others. Below are a few examples that illustrate various substrate issues that have recently come across the transom which feature acceptance--by the concrete contractor—of another contractor’s work product. And, as any veteran concrete contractor can tell you, one of the most hazardous features of a double-edged sword is that it is an equal-opportunity blade that can slice both ways. Concrete Mat Slab Foundation (Earthwork Substrate) • Tolerances for top of subgrade substrate elevation are typically found in Division 31 specifications (formerly Division 2), civil/shoring drawings or the project geotechnical report. Rule of thumb: rough grade tolerance of plus or minus 0.1 ft., assuming a mud or working slab will be installed on top of the prepared substrate. In rare cases where the mat is placed directly on top of the subgrade, the plus tolerance would be 0.06 ft (the ACI 117 slab thickness tolerance of minus ¾ inch would govern). • Prior to accepting the earthwork substrate, insist on receiving a licensed surveyor’s certification drawing confirming the pad has been graded within tolerance, including at all contours, slopes and elevation changes. Also, request certification that the geotechnical engineer has signed off on the pad substrate preparation before taking ownership and starting concrete work. • For pad substrates with constant elevation, spot-checking can easily be self-performed using typical survey layout instruments. Access to a laser scanner is another efficient way to check the quality of the substrate preparation and, if needed, to run a reasonably accurate volume calculation for actual concrete quantity required for the mud slab. If the scan indicates the substrate is low and will require extra concrete, suggest submitting the scan results to the GC in a timely manner for review by the earthwork sub and/or the surveyor. Perimeter Sheeting and Shoring (Soldier Pile/Lagging Substrate) • This condition assumes there are several levels below grade, and that concrete foundation walls are either CIP or shot against a waterproofing membrane attached to the shoring substrate. • Tolerances for placement of the shoring system are typically included in the general drawing notes prepared by the shoring specialty engineer. For soldier piles, assume a tolerance of 2 inches (away from the structure) and zero tolerance for mislocated substrate encroaching on the nominal design thickness of the structural concrete foundation walls. • Similar to the earthwork substrate, insist on a certified survey confirming the as-built location of the shoring system before starting work. In cases where the shoring system substrate encroaches on the wall thickness, the structural engineer will need to know straightaway. Changes to the wall reinforcement, concrete strength, or formwork may be required by the LDP. Relocation of the substrate is generally not an option. • Attempting to spot-check several levels of shoring substrate behind the surveyor is typically impractical to self-perform. This is another time when a laser scanner can quickly determine if the substrate is installed correctly, and-- if needed-- can quickly run a volume calculation for actual concrete quantities required to place the foundation concrete walls. • In most cases where several levels of substrate below grade require waterproofing, the waterproofing consultant should also certify the waterproofing installation is acceptable before accepting the substrate and starting the concrete scope. Structural Steel Buildings (Metal Deck Substrate) • According to ACI 117-10, section 4.4.1, there is actually no tolerance requirement for location of top of concrete slab placed on a metal deck substrate. This is one work scope where almost all of the slab formwork typically installed by the concrete contractor (e.g. soffits and slab edges) are now installed in sheet metal by others. Responsibility and risk associated with tolerances for slab edge locations, opening sizes/locations and other substrate features are also shifted outside of the concrete contractor’s scope. • In some cases, the timing of acceptance of a metal deck substrate by the concrete contractor can come into play, especially in the case of multi-story buildings. Consider the case of the ASCC member who bid a multi-story deckfill pump-place-finish project assuming the floors would be placed using a 25 percent flyash mix during the summer. After schedule delays pushed the work into the winter, the member’s labor costs to install the work increased dramatically. The cold, plus the fact that the decks below roof level were shaded from direct sunlight, meant longer than anticipated crew days. In this case, the contractor accepted the substrate, but used ASCC Position Statement #15 “Setting Time Expectations for Hard-Troweled Concrete” to substantiate his request for change order to cover costs associated with crew overtime and accelerating admixture. • Another metal deck substrate booby trap is one that actually needs to be neutralized during bid time, long in advance of the work. This one involves design call-outs in many project specifications requiring metal deck panels to be vented, presumably with the idea that allowing mix water to drip through the deck somehow enhances the application of follow-on flooring. In a Position Statement issued by the Steel Deck Institute, the SDI explains that--in most cases-- vented deck is not required, and slabs on metal deck should be considered similar to slabs-on-grade placed on vapor barrier when assessing potential moisture issues. For the concrete contractor, vented deck adds labor costs to the project for clean-up during and after placements. It is in the owner’s best interest for the concrete contractor to question the need for this particular substrate item during bid time. Foundation Mat Reinforcing Steel (Waterproofing Substrate) • On some projects, a protection slab or protection board is specified to protect a waterproofing membrane from damage during installation of reinforcing steel and other follow-on work installed by multiple trades. On other projects, the mat slab reinforcing steel is placed directly on top of the waterproofing membrane substrate. Despite all good intentions, damage to the membrane substrate inevitably occurs when tons of reinforcing steel bars are placed production-style on schedule-driven projects. Suggest writing a qualification clause in bid proposal letters that excludes the cost of such “trade damage” and instead request the owner carry an allowance to cover repairs of incidental damage to the waterproofing membrane substrate. If this approach is unsuccessful, suggest photographing the entire surface of the waterproofing membrane prior to accepting the substrate and then carefully monitoring the work of all trades (rebar, electrical, plumbing) who can possibly contribute trade damage. Since the backcharge costs to repair waterproofing substrate can quickly escalate, this topic should be discussed with all parties—including the waterproofing inspector-- during the preconstruction conference and before the concrete contractor accepts the substrate. rzuellig Sat, 15 May 2021 16:54:00 GMT f1397696-738c-4295-afcd-943feb885714:44