How to Cure Concrete in the Winter

It is possible to cure concrete during the winter, as long as the concrete is kept warmer than 50 degrees for at least five days or warmer than 70 degrees for about three days. One way to do this is by using portable hydronic heaters.

Things You'll Need

• Portable hydronic heater(s) Sand or gravel Forms Mixed wet concrete Rakes Screeding board Float Polyethylene sheet Insulation blankets

Instructions

1. Place heat transfer hoses about 24 inches apart on the excavated area where the concrete will be poured. Cover the area with insulation blankets. Run the heater until the ground is completely thawed. Usually, frozen soil thaws at about 1 foot each 24 hours.

2. Remove the heat transfer hoses. Fill the thawed excavated area with about 2 inches of sand, gravel or recycled concrete. Use a tamper to compact the base thoroughly. Grade the surface.

3. Place the heat transfer hoses on the sand in a 24-inch grid. Cover the area with insulation blankets. Run the heater until the sand is about 35 degrees. Sand will usually heat at a rate of 1.5 to 2 degrees each hour. You can build the concrete forms while the sand is heating.

4. Remove the blankets and the heat transfer hoses. Pour, screed and float the concrete as usual.

5. Cover the poured concrete with a polyethylene sheet as a vapor barrier. Arrange the heat transfer hoses as before, and cover the entire surface with insulation blankets. Adjust the system temperature so that the hoses are between 65 and 75 degrees.

6. Maintain the heat for three to seven days, until the concrete is cleared.

Tips & Warnings

• Wear heavy rubber boots and work gloves when handling concrete. Portable hydronic heaters can be rented from many equipment rental companies.

• If you get wet concrete on your skin, wash it off promptly. Rinse your skin with vinegar at the end of the work period to neutralize the alkalinity of the concrete.

Resources

• The Portland Cement Association