Why is air-entrained concrete typically specified for highway pavement in climates with freezing and deicing salts?

1. Entrained air makes the concrete heavier so it needs no base
2. A system of microscopic air voids relieves pressure from freezing water and improves freeze-thaw and salt scaling resistance
3. Air entrainment replaces 50% of the coarse aggregate
4. Air-entrained concrete never needs joints