Airentrained

Airentrained, or air-entrained, refers to cementitious mixes that incorporate a controlled distribution of microscopic air voids formed during mixing by air-entraining agents (AEA). These voids are very small and evenly dispersed through the hardened paste, typically on the order of tens to a few hundred micrometers in diameter.

The primary purpose of the air void system is to provide space for water to expand when it freezes. This reduces internal pressures that would otherwise crack the concrete, thereby improving resistance to freeze–thaw cycles and scaling in cold or deicing-salt environments. In addition to durability, air-entrained mixes can improve workability, reduce bleeding and segregation, and help with pumpability and finishing.

Typical properties of air-entrained concrete include an air content of roughly 3 to 7 percent by volume and an air-void spacing factor around 0.2 millimeters or less, with voids commonly measured in the 50 to 200 micrometer range. The exact dosage of AEA depends on climate, exposure, paste quality, and desired properties.

Applications are common in structures exposed to freezing and thawing, such as pavements, bridges, and building foundations in temperate and cold climates. However, excessive air can reduce density and compressive strength, so dosage must be carefully controlled and tested. Standards and testing typically involve measuring fresh-air content (for example by pressure methods) and analyzing the hardened air-void system to ensure the spacing and void distribution meet durability requirements.