Commonly used air-entraining agents, whether vinsol resins or multicomponent organic materials, usually reduce concrete strength. Also, air content may increase or decrease markedly with increased slump or mixing time. A newly developed air-entraining agent avoids these problems by producing bubbles with thicker walls. Several benefits are claimed for the improved air void system: increased concrete strength; better distribution of air voids; more uniform bubble size and shape; less bubble coalescence during mixing and placing; and fewer bubble clusters at aggregate particle surfaces. The improved air-entraining agent is a modified cocamide DEA.

AIR CONTENT AND STRENGTH LOSS

Typical strength loss in air-entrained concrete is 2% to 6% for each percent of air entrained. But air-entrained concrete with cocamide DEA is stronger than non-air-entrained concrete at cement contents up to 650 pounds per cubic yard. At similar air contents, concrete with cocamide DEA was stronger than that with vinsol resin.

DIFFERENCES IN AIR VOID SYSTEMS

Air voids sometimes cluster on the surface of coarse aggregate particles. They also may coalesce to form larger irregularly shaped bubbles. Specimens with cocamide DEA showed no significant amount of coalesced air voids or air void clusters on coarse aggregate particles.