Air entrained concrete can be produced by either using air entraining Portland cement or by the careful addition of an air entraining agent to the fresh concrete as it is being mixed. The air bubbles that are created are typically 10-500 microns in diameter.
Some effects of entraining air into a concrete are:
The recommended entrained-air content of concrete depends on the size of its coarse aggregate. If the recommended entrained-air content is exceeded, the concrete may suffer from severe losses in compressive strength.
Certain admixtures, such as superplasticisers can also cause unintentional air entrainment in the concrete. Polycarboxylate-based superplasticisers in particular are known to entrain a lot of air in certain conditions; so much so that they often come already mixed with a defoaming agent to help limit their air-entraining effect.
The use of air entraining agents in concrete that is to be power trowelled should be avoided if possible due an increased risk of delamination.