| Air-Entrained Concrete
of the greatest advances in concrete technology was the development
of air-entrained concrete in the late 1930s. Today, air entrainment
is recommended for nearly all concretes, principally to improve
resistance to freezing when exposed to water and deicing chemicals.
However, there are other important benefits of entrained air in
both freshly mixed and hardened concrete. Air-entrained concrete
contains billions of microscopic air cells. These relieve internal
pressure on the concrete by providing tiny chambers for the expansion
of water when it freezes.
concrete is produced through the use of air-entraining portland
cement, or by introducing air-entraining admixtures under careful
engineering supervision as the concrete is mixed on the job. The
amount of entrained air is usually between 5 percent and 8 percent
of the volume of the concrete, but may be varied as required by
special conditions. The use of air-entraining agents results in
concrete that is highly resistant to severe frost action and cycles
of wetting and drying or freezing and thawing and has a high degree
of workability and durability.
How Cement is Made
& Finishing Concrete