Slump and Concrete Strength of Air Entrained Concrete

During the making of concrete a slump test is mandatory and normally slumps of about 3 inches are used for good workability. However when air entraining agents are used, the slump can reduce to between 1 to 2 inches while still having the same desired workability. The air entrained concrete has a whipped cream effect that allows slump reduction. Engineers take advantage of this slump reduction to further reduce the water-to-cement ratio in the concrete which can increase the strength of the concrete.

Strength of air entrained concrete reduces 5 percent for every 1 percent of entrained air. This can be compensated by the reduction in the water-to-cement ratio or by reduction in fine aggregates, but these are matters better decided by structural engineers designing the structure. The reduction in strength comes from the voids caused by the entrained air.

The amount of entrained air is maintained between 4 and 7 percent for best freezing thawing resistance though variations can be made depending on specific conditions.