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