The American Society of Concrete Contractors (ASCC) has published its 44th Position Statement, “Measuring Air Content in Non-Air-Entrained Concrete.” ASCC Position Statements clarify the concrete contractors’ point of view for architects, engineers, owners and others.
Position Statement No. 44 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.
Specifications such as ACI 301 and MasterSpec 033000–Cast-in-Place Concrete require a maximum air content in concrete floors to receive a hard-troweled finish, and 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,” says Suprenant, “due to the probability of blistering or delamination occurring as a result.”
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% 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, says Suprenant. Thus, in Position Statement No. 44, ASCC contractors encourage owners to direct specifiers to require measuring the air content of concrete to receive a hard-troweled finish.