SEDL / STP / STP169-EB / STP39434S

Air Content and Unit Weight

Helms, SB
Research Engineer, Lehigh Portland Cement Co., Allentown, Pa.

Pages: 13    Published: Jan 1956

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Abstract

In this discussion of certain aspects of the effect of entrained air in concrete, the principles developed by early investigators are referred to first. The pioneers could not forsee the real benefits that would result from air entrainment, but they did develop some elementary physical relationships which are still pertinent. In the days of Feret's studies (1), the density of mortar was represented by the total volume of the solid particles. This could be termed the first application of the method of absolute volumes, which is involved both in proportioning and in the analysis of physical constants of concrete. To develop the relationship for compressive strength, P, using constants J and K, Feret assigned letters (c for cement, s for sand, e for water, v for air voids) to represent the absolute volumes of mortar constituents and proved from his data the validity of the relationships: P=J(c1-(c+s)-0.1) and: P=K(c1-s)2