Q: I know that entrained air improves concrete's resistance to freeze/thaw damage, but why would air-entrained concrete be required in an area where freeze/thaw isn't an issue?
A: Entrained air does help resist freeze/thaw damage and deicer scaling, but it can be helpful in other ways as well. It increases the workability of concrete, especially in mixes that otherwise could be difficult to work due to low-cement content or poorly graded aggregates. Entrained air can produce a workable mix with less water and sand than a non-air-entrained concrete. It also reduces segregation and bleeding in fresh concrete.
When used to reduce the water-cement ratio, air entrainment can improve concrete's resistance to attack from sulfate soils and waters. It also helps concrete resist damage from alkali-silica reactivity. Increased air content reduces the amount of expansion in concretes made with reactive aggregates, thereby reducing deterioration.