Technical Questions

ACI Committees, Membership, and Staff have answered common questions on a variety of concrete related topics.

The effect of entrained air on the workability of concrete

Q. How does entrained air effect the workability of concrete?


A. Even though the main function of the entrained air is to provide resistance to cycles of freezing and thawing, it can also improve the workability of concrete. In the finer size range, the air bubbles can reasonably be considered to form part of the paste, and to such extent affect its plasticity and increase its volume. In the coarser size range, the air bubbles may perform more like deformable fine aggregate particles. In either case, the effect would be in the direction of improving workability. Regardless of the explanation, the improved workability through air entrainment is a fact of observation.

Considerable variation in air content is a troublesome cause of variation in slump and strength. Accordingly, air entrainment is not recommended when its only benefit is better workability. This is more uniformly obtained by the use of a water-reducing admixture (ACI 212.3R) and a pozzolan (ACI 232.2R, ACI 234R) or slag (ACI 233R). These ingredients also provide other considerable benefits.


References: SP-1(02); E4-12; E3-13; ACI 212.3R-16; ACI 232.2R-03; ACI 234R-06; ACI 233R-03

Topics in Concrete: Admixture; Concrete Fundamentals; High Performance Concrete; Mixture Proportioning

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