The most potential destructive weathering factor is freezing and thawing while the concrete is wet.

Deterioration is caused by the freezing of water and subsequent expansion in the paste, the aggregate particle or both.

With the addition of an air entrancement admixture concrete is highly resistance to freezing and thawing.

The microscopic air bubble in the paste provide chamber foe water to enter and thus relieve the hydraulic pressure generated.

Air entrained concrete with a low water cement ratio and an air content of 5 to 8% will withstand a great number of cycle of freezing and thawing without distress.

Effect of weathering freezing and thawing

1) lack of durability of concrete due to freezing and thawing of frost is not so important in Indian condition. But is of great importance in cold country.

2) As the temperature of saturated harden concrete is lowered the water help in the capillary pores in the concrete freezes in a similar manner to the freezing in the capillary in rock and expansion of concrete take place. Hence it concrete mass subjected to alternate cycle of freezing and thawing. It has detrimental effect in strength of concrete.

3) Hence while concreting in cold weather the temperature of fresh concrete should be maintain should be above zero Degree.