COLD WEATHER CONCRETING
What is considered “cold weather”?
For concreting purposes, cold weather is classified as any period of time longer than 3 consecutive days during which the average temperature is less than 40ºF (5ºC) and air temperature less than 50ºF (10ºC) for more than 12 hours per 24 hour period.
Why worry about cold weather?
Placing, finishing, curing, and protecting concrete under these conditions warrants special regard to proper procedure to ensure the longevity of your concrete. The potential strength of concrete will be significantly compromised if allowed to freeze in a fresh state. Steps should be taken to protect concrete from freezing until at least two days after placement. Additionally, excessive temperature differences between the surface and the interior of the concrete may lead to thermal cracking. Proper insulation is a necessity to avoid issues during the process.
How to place concrete in cold weather:
Section size will dictate appropriate concrete temperature for the specific job. For sections less than 12″, concrete should be 55º, for 12″ to 36″, 50º, and for 36″ to 72″, 45º. Care should be taken to avoid exceeding suggested temps by more than 20º as more mixing water will be required, increasing the susceptibility of cracking. When utilizing a chemical admixture to accelerate finishing, bear in mind that the concrete must still be kept from freezing to avoid potential structural issues.
Adapted from IRMCA – CIP 100