Source: American Society of Concrete Contractors, St. Louis
The latest ASCC position statement, “Measuring Air Content in Non-Air-Entrained Concrete,” conveys contractors’ point of view for architects, engineers, owners and others. The document explains that while air content is reported in the mix design submitted for air-entrained concrete and measured in the field for compliance, air content measurements are rarely specified or measured for non-air-entrained concrete.
Widely referenced specifications cite maximum air content in concrete floors to receive a hard-troweled finish for good reason, according to ASCC Technical Director Bruce Suprenant, PE, PhD, FACI. “Air-entraining admixtures should not be specified or used in concrete to be given a smooth, dense, hard-troweled finish due to the probability of blistering or delamination,” he explains.
ASCC contractors have observed that when water-reducing and/or waterproofing admixtures are used in concrete to receive a hard-troweled finish, air contents often exceed the 3 percent maximum set out in ACI 302.1R-15, Guide to Concrete Floor and Slab Construction. Often contractors aren’t alerted to this issue because the air content isn’t measured, notes Suprenant. Consequently, the new position statement concludes, contractors should encourage owners to direct specifiers to require measuring the air content of concrete to receive a hard-troweled finish. — www.ascconline.org