Cold Weather Concrete

ACI 306 defines cold weather concrete as a period when temperatures fall below 40 degrees Fahrenheit for 3 consecutive days.  There are many precautionary steps required when placing concrete in cold weather. Proper planning can eliminate many of the risks involved when placing under these conditions.

Water inside concrete will begin to freeze at approximately 30° F. When water freezes it can expand up to 9% its original volume. This will cause cracking and ultimately failure of the concrete. Up to 50% of the concretes potential strength can be lost if it is allowed to freeze before it reaches adequate strength. The concrete should be allowed to reach 3500 PSI before it is exposed to freezing and thawing or deicing chemicals. A non-chloride accelerator can be used to help protect the concrete from freezing.

Cold Weather Concrete Tips:

· Use air entrained concrete exposed to freezing and thawing

· Keep surfaces exposed to concrete free from ice and snow and above freezing prior to placement

· Place and maintain concrete at the recommended temperature

· Protect plastic concrete from freezing and drying

· Protect concrete from freezing and thawing cycles until adequate strength is reached

· Limit rapid temperature changes during curing period

· Setting Time of Concrete at Various Temperatures

· 70 °F      - 6 Hours

· 60 °F      - 8 Hours

· 50 °F      - 11 Hours

· 40 °F      - 14 Hours

· 30 °F      - 19 Hours

· 20 °F      - Set does not occur–concrete will freeze

Source: “Concrete Construction”, March, 1990