COLD WEATHER CONCRETE CURING
Your semi-frozen hands tough it out to complete the concrete cutting and concrete coring work no matter how cold the conditions - just another day at the office. When it comes to concrete curing, however, the temperature can’t just be ignored.
Concrete work in freezing conditions requires extra layers on your back and a few more layers to your process.
KNOW YOUR TEMPS & TIMING
Concrete cured in colder temperatures can cure stronger because of the slower curing process. However, those who don't do concrete cutting, coring, and other masonry work every winter will want to note the following about curing:
- Concrete at 70 degrees takes approximately 5 hours to set and at 30 degrees, up to 20 hours It is critical that the concrete not be allowed to freeze during the first 1-2 days, particularly.
- If the ambient (or air) temperature is under 40 degrees, it’s considered cold weather concrete. Surface temperature is the temperature of the formwork, rebar, ground, existing curb or anything touching the concrete to be poured. All surface temperatures need to be over 10 degrees. If it’s under 10 degrees outside, there’s a good chance your surface temperatures will be too cold.
- The delivery temperature is the temperature of delivered concrete. For a concrete slab that is going to be less than 12 inches thick, the delivery temperature should be about 65 degrees Fahrenheit. The delivery temperature varies, so check the ACI Delivery Temperature Table for the correct delivery temperature for your specific project variables.
- Also check your ACI code book for cooling rates (acceptable rates for your concrete to lower in temperature to the ambient temperature) and use a temperature gun or other such tool to monitor.