Precautions to be Taken in Cold Weather Concreting:

Proportioning of Concrete Ingredients

The quantity of cement in the mix affects the rate of increase in temperature, an additional quantity of cement may be used. It would be preferable to use high alumina cement for concreting during frost conditions. The main advantage is that a higher heat of hydration is generated during the first 24 hours. During this period, sufficient strength (approximately 10 to 15 MPa) is developed to make the concrete safe against frost action. No accelerator should be used if high alumina cement is used. Alternatively, the rapid hardening Portland cement or accelerating admixtures used with proper precautions can help in getting the required strength in short period. Air-entraining agents are generally used in cold weather. Air-entrainment increases the resistance of hardened concrete to freezing and thawing and normally, at the same time, improves the workability of fresh concrete. The calcium chloride used as accelerating admixture may cause corrosion of reinforcing steel. In some case, calcium chloride should not be used in pre-stressed concrete construction. The important factor for cold-weather concreting is the attainment of suitable temperature for fresh concrete.