The American Society of Concrete Contractors (ASCC), St. Louis, MO, has published its 44th Position Statement, “Measuring Air Content in Non-Air-Entrained Concrete.” ASCC position statements clarify the concrete contractor’s point of view for architects, engineers, owners, and others.
Position statement 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. “Air-entraining admixtures should not be specified or used in concrete to be given a smooth, dense, hard-troweled finish,” he says, “due to the probability of blistering or delamination occurring as a result.”
ASCC contractors have observed that when water-reducing or waterproofing admixtures are used in concrete to receive a hard-troweled finish, air contents often exceed the 3% maximum s et 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, position statement 44 concludes, ASCC contractors encourage owners to direct specifiers to require measuring the air content of any concrete that is to receive a hard-troweled finish.
ASCC is a non-profit organization dedicated to enhancing the capabilities of those who build with concrete, and to providing them a unified voice in the construction industry. Members include concrete contracting firms, manufacturers, suppliers, and others interested in the concrete industry, such as architects, specifiers, and engineers. There are 770 member companies in the United States and 13 foreign countries. For more information visit the website at www.ascconline.org or call 866-788-2722.
