An air-entraining admixture stabilizes tiny, closely spaced bubbles, mostly 10 to 1,000 microns across, that give freezing water room to expand without cracking the paste. Exterior concrete in freeze-thaw climates usually targets 5 to 7 percent total air, checked with an air meter at the truck. Each percent of air costs roughly 5 percent of compressive strength, and the larger entrapped air voids left by mixing give no frost protection at all.
Air came in at 3.5 on the sidewalk mix, send it back and tell dispatch the spec is six plus or minus one and a half.
Also heard as
- air
- AE
- entrained air
- air-entrained concrete
Related terms
Air meter
A sealed pressure vessel used at the truck to measure the air content of fresh concrete.
Scaling
Thin patches of surface mortar coming off a slab, usually after freeze-thaw cycles with deicing salt.
Delamination
A surface layer that has split away from the concrete below it, found by the hollow sound it makes when tapped.
Admixture
A product dosed into a concrete batch, usually by the ounce, to change its flow, set time, air or durability.
Fly ash
Fine powder captured from coal-fired power plant exhaust, used to replace part of the cement in concrete.