What is the defining feature of entrapped air in concrete?

Entrapped air in concrete is characterized by air voids that are typically 1mm or larger. This type of air occurs naturally during the mixing process when larger air bubbles are trapped within the concrete mix. These voids can significantly impact the concrete's properties, including its durability and resistance to freeze-thaw cycles.

The presence of these larger voids is different from entrained air, which involves intentionally adding air-entraining agents to produce smaller, uniformly distributed air bubbles that improve the workability and performance of the concrete. Therefore, understanding that entrapped air consists of larger voids helps clarify its defining feature.