It is common practice to use air-entrained concrete in exposed slabs such as driveways and large concrete car parks.
Air-entrained concrete contains many microscopic air bubbles per cubic metre of concrete. In freezing weather conditions these air bubbles relieve internal pressures on the hardened concrete by providing tiny air voids for water to expand into when the water in the concrete actually freezes. Without entrained air the expanding freezing water will break up the concrete surface and possibly the internal structure of hardened concrete. Some very strong concretes may also resist these freeze thaw cycles without air entrainment.
Air-entrained concrete is produced using air-entraining admixtures when the concrete is batched. The amount of entrained air is usually between four and seven percent of the volume of the concrete, but may be varied as required by special conditions.