Air tests for nonair-entrained concrete

Q. Is it necessary to conduct jobsite tests for air content when the concrete is nonair-entrained?

A. ASTM C94 “Standard Specification for Ready-Mixed Concrete” does not explicitly address the case of nonair-entrained concrete. ASTM C94 requires air content to be tested for concrete that will be exposed to cycles of freezing and thawing. Therefore, it could be concluded that unless otherwise required by the construction documents, non-air-entrained concrete not exposed to freezing and thawing does not have to be tested for air content.

Note that it is recommended to require air content testing for non-air-entrained concrete used for floors and slabs. ACI 301-16 “Specifications for Structural Concrete” require the total air content of hard-troweled interior concrete floors to not exceed 3 percent. According to ACI 302.1R-15 “Guide to Concrete Floor and Slab Construction”, air contents in excess of 3 percent make the surface difficult to finish and can lead to surface blistering and peeling during finishing. Concrete mixtures for slabs do not commonly contain air-entraining admixture, however, the presence of other admixtures could unintentionally entrain air in concrete and cause delamination.

References: ACI 301-16; ACI 302.1R-15; ASTM C94

Topics in Concrete: Durability; Mixture Proportioning; Slab; Quality Assurance; Testing