Pouring concrete for a large project can be challenging in the best weather, but when conditions are cold it becomes even more so. "Cold weather" is generally agreed to be three or more days when the temperature goes below 40 degrees F. The cold air and ice crystals conspire to weaken and even fracture concrete. There are many steps that you can take to prevent this if you must pour in cold weather.
Things You'll Need
- Plastic tarp
- Cement mixer
- Thermal blankets
Spread a 6-inch layer of straw over the pour site, covered with a plastic tarp, to protect against freezing temperatures the night before the pour. Remove this insulating layer before pouring.
Ensure that the aggregate is thawed before adding it to the mixer. Frozen aggregate will release water as it thaws, making the mix too thin if it happens in the mixer.
Increase the temperature of the water used to up to 180 degrees F. Add this water to the aggregate before adding the cement -- hot water poured directly into cement can cause flash setting.
Increase the amount to cement in the mixture, producing a drier mix. This additional cement will release more heat as it cures, helping to keep the concrete warm longer.
Add an accelerator such as calcium chloride to the mixture. This will help the concrete to cure faster. Faster curing means less time for ice crystals to form within the concrete.
Cover the cement with thermal blankets after pouring, as soon as it has hardened enough that the blankets will not affect the surface texture. These blankets will trap heat while the concrete cures. Leave them in place for several days.
Tips & Warnings
- Consult a local concrete supplier for advice on local concrete requirements. They may recommend that one or more of these steps be omitted due to the conditions of your area.
- Concrete Contractor; Cold Weather Pouring Techniques; John Kulczycki; 2011
- Log Home Builders: Pouring Concrete in Winter
- "Complete Do-It-Yourself Manual: Completely Revised and Updated"; Reader's Digest; 2005
- Photo Credit Jupiterimages/Photos.com/Getty Images