What is air entrained concrete and why is it important?
Air entrained concrete has an intentionally added air entraining admixture that puts microscopic air bubbles into the concrete. The purpose of the air bubbles is to provide durability for concrete exposed to freezing and thawing. Concrete that is wet in service, such as a sidewalk or a driveway, and exposed to freezing and thawing, must be air entrained to be durable. Water that is absorbed by the concrete expands when it freezes. The air bubbles give the water room to expand, which greatly reduces the internal pressure created when water freezes. If the concrete were not air entrained, this internal pressure would rupture the surrounding concrete, causing severe deterioration of the concrete. The American Concrete Institute recommends 4.5-7.5% entrained air in concrete made with 1″ maximum size coarse aggregate when such concrete is subjected to severe freeze thaw exposures.
