How cold is too cold to pour concrete? And what should you do if it’s sweltering hot, but you need to make a concrete repair? While you can pour concrete in cold and hot weather, it’s necessary to take certain precautions to ensure the concrete sets properly.
First, it’s not only important to consider ambient temperature but also how you will keep the concrete at the correct temperature while it cures. During cold weather, many people use heated enclosures or insulated blankets to prevent the concrete from freezing. Alternatively, windbreaks, sunshades, evaporative retarders and sufficient manpower are necessary for proper curing during hot temperatures.
Learn more about hot and cold weather concrete procedures, concrete curing temperature ranges and tips for curing below.
Temperature Ranges for Pouring Concrete
Experts agree—the best temperature to pour concrete is between 40° – 60°F. When temperatures dip below 40°F, the chemical reactions that strengthen concrete slow down and can lead to weaker concrete. If concrete curing temperatures are below freezing, the water inside the concrete can freeze and expand, resulting in cracks.
According to the American Concrete Institute, hot weather is more than air temperature. Hot weather is defined as ambient temperatures above 90°F—including low humidity and high wind speeds. In conditions hotter than 77°F, the water used to hydrate and cure the cement can evaporate, increasing the concrete’s temperature and presenting problems such as weakness, shrinkage and cracking.
However, proper precautions help you successfully pour concrete during hot or cold weather. Here are some tips to ensure your concrete project is done the right way—even if you’re working outside that ideal 40° – 60°F window.
Tips for Pouring Concrete in Cold Weather
Maintaining the correct temperatures for the concrete curing process is extremely important. Concrete must set before it is exposed to freezing temperatures. You can overcome cold weather challenges by following the tips below:
- Store concrete materials in a warm, dry place.
- Thaw frozen ground, snow or ice with heaters.
- Use cold weather products designed to cure fast.
- Use hot water to mix your concrete.
- Create a hotter reaction by using extra cement (e.g. 100lb. per cubic yard).
- Use squeegees or a vacuum to quickly remove bleed water.
- Do not remove frameworks until the concrete has cured.
Tips for Pouring Concrete in Hot Weather
If you’re pouring concrete in hot weather that exceeds 77°F, it’s important to plan ahead. Offset detrimental effects from heat, humidity and wind with the following tips:
- Avoid pouring during the hottest parts of the day.
- Use sunshades or windbreaks for protection.
- Store bags of concrete in the shade, garage or other cool area before using.
- Dampen the subgrade before pouring your concrete slab.
- Add ice to your concrete water mix to help cool down temperatures.
- Once water is added to the mix, reduce mixing time.
- Make sure you have help—from managing the pouring to overseeing the curing process.
Pouring concrete in hot or cold weather is possible when you take the right steps and work quickly. Keep in mind, set times will vary depending on temperature, no matter the time of year. For professionals and homeowners alike, pouring concrete can be a nerve-wracking experience—but it doesn’t have to be. With careful planning, you can achieve good results in less-than-ideal temperatures.
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