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Hot Weather Concrete
What is it?
Hot weather* is any combination of the following conditions that tend to impair the quality of freshly mixed concrete by accelerating the rate of moisture loss and rate of cement hydration or otherwise causing detrimental results:
- High ambient temperatures
- High concrete temperatures
- Low relative humidity
- High wind speed
- Solar radiation
*Hot weather conditions can occur during the spring, fall, and winter months.Â
The following is a list of practices and measures designed to reduce or avoid the potential problems of hot weather concreting:
- Schedule a pre-placement meeting to discuss the requirements of hot weather concreting.
- Select concrete materials and proportions with satisfactory records in hot weather conditions.
- Reduce and control the temperature of the fresh concrete.
- Use a concrete consistency (slump) that permits rapid placement and effective consolidation.
- Minimize the time to transport, place, consolidate and finish the concrete.
- Plan the concrete placement to avoid adverse exposure of the concrete to the environment; schedule placing operations during times of the day or night when weather conditions are favorable.
- Protect the concrete from moisture loss during placing and curing period.
Potential hot weather problems for concrete in the freshly mixed state include:
- Increased water demand
- Increased rate of slump loss and corresponding tendency to add water at the job site.
- Increased rate of setting, resulting in a greater difficulty with handling, compacting and finishing and a greater risk of cold joints.
- Increased tendency for plastic shrinkage and thermal cracking.
- Increased difficulty in controlling air-entrained content.
Potential hot weather problems for concrete in the hardened state include:
- Decreased strengths resulting from higher water demand.
- Increased tendency for drying shrinkage and differential thermal cracking from either cooling of the overall structure or from temperature differentials within the cross-section of the member.
- Decreased durability resulting from cracking.
- Greater variability of surface appearance, such as cold joints or color difference due to different rates of hydration or different water cementitious material ratios (w/cm).
Hot Weather Products
Our Cemstone Supply stores sell several products for hot weather concreting. If the evaporation rate in your area approaches 0.2 lbs/ft2/hr, use the following concrete evaporation reducers:
*Hot weather conditions can occur during the spring, fall, and winter months.
Interested in learning more? Click here to see our complete hot weather concrete guide, including valuable information from the American Concrete Institute.
