Cold weather is defined as any period when the average daily air temperature is less than 40° F or less than 50° F for more than 12 of any 24 hour period on more than 3 consecutive days. Slabs lose moisture and /or heat rapidly in cold weather which affects setting time, strength gain and long term durability of the concrete. Cold weather:
•  Can freeze mix water, reducing concrete strength up to 50%.
•  Increases concrete set time up to one-third for each 10° F decrease in air temperature.
•  Retards concrete stiffening.

Tips for Protecting Concrete in Cold Weather
•  Warm the subgrade, the forms, and any reinforcing steel-don't place concrete on frozen subgrade.
•  Maintain concrete temperature above 50° F by insulating or heating for three days. Use insulation blankets to retain internal heat generated by the concrete or provide heaters for the scheduled concrete placement.
•  Use heated enclosures to block wind, keep out the cold, and conserve heat.
•  Use air-entrained concrete.
•  Use proper curing methods as soon as possible. Cure to protect against freezing until concrete reaches 500-psi compressive strength (usually about 2 days at 50° F).
•  Contact your Prairie salesperson to discuss heating water and aggregates, or adding a non-chloride accelerating admixture, increasing cement content or using Type III Cement.
•  Protect concrete against multiple freeze-thaw cycles until it reaches 3500-psi compressive strength.

To Lessen Carbonation Damage
•  Use a water cure or a membrane curing compound and block carbon dioxide gas from the concrete. Membrane film should be uniform and heavy.
•  Use an accelerating set admixture in the concrete.
•  Use vented heaters.
•  Open the building to fresh air during pouring to ventilate exhaust fumes from trucks, troweling machines, etc.