Plastic shrinkage results in cracking. After setting, further shrinkage, known as drying shrinkage, may happen. If restrained, drying shrinkage strains can cause cracking of concrete and eventually imay ncrease the deflection of concrete members. Concrete under sustained stress undergoes a gradual increase of strain with time. Permeability largely affects the durability of hardened concrete.
Permeability is inversely proportional to the water-cement ratio.
Age of concrete, fineness of cement particles, and air-entraining agents also influence the permeability.