What is air-entrained concrete ?

Air-entrained concrete contains billions of microscopic air cells percubic foot . These air pockets releive internal presseure on the concrete by providing tiny chambers for water to expand into when it freezes . AIr -entrained concrete is produced through the use of air-entraining portland cement , or by the introduction of air-entraining agents , under careful engineering supervision as the concrete is mixed on the job . The amount of entrainrd air is usually between 4 percent and 7 percent of the bolume of the concrete , but may be varied as rewuited by special conditions