Concrete By Any Other Name

Posted on August 01, 2021 in: Technical

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.

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