Additional aerosols cause uniformly stable tiny air bubbles to form through the concrete mixture. Bubbles are mostly less than 1mm in diameter with a high percentage of less than 0.3mm. The benefits of air stripping in concrete include increased resistance to freeze-thaw degradation, increased cohesion (resulting in reduced bleeding and segregation) and improved compaction in low workable mixes.
This is unreasonable to me. By introducing more voids into the concrete, there are more water ingress pathways which can expand and crack the concrete.
Why does air retention additive improve concrete’s freezing and thawing resistance?