How Much Time Does It Take to Cure Cement?

Time

• Concrete slabs for driveways, sidewalks, patios and other pavements must be cured for at least seven days before use. The same seven-day curing interval applies to structural concrete in columns, piers, beams and walls. During this time, concrete will develop about 70 percent of its ultimate strength. But, concrete continues to cure, at a slower rate, for at least three more weeks. The seven-day curing interval is typical for most types of construction concrete, but some specialized mixtures can reach the 70-percent strength point in as little as three days or as long as 14 days.

Temperature Level

• New concrete should be cured at temperatures between 50 and 80 degrees Fahrenheit during the initial curing week. Cold weather slows curing; concrete at 50 F gains strength half as fast as at 70 F. At 40 F, curing stops before full strength has been achieved. Concrete cures fast at temperatures above 80 F but it can also dry out quickly, which halts the curing process and leads to weak concrete.

Temperature Control

• Curing during very cold or very hot weather requires special procedures. When air temperature is below 50 F, use insulating blankets, heated blankets, heated enclosures, steam fogging or heating coils to keep the concrete warm enough for curing. Concrete in hot weather above 80 F must be protected from drying out by sunscreens, windscreens, frequent surface fogging with water, or chemical coating compounds that reduce surface evaporation.

Moisture

• Fresh concrete must be kept moist during the initial week of curing. There are several methods for moistening concrete. On small jobs, you can use watertight barriers to keep a shallow pond of water on flat horizontal concrete surfaces. On larger jobs, spraying or fogging with water works when temperatures are warm and humidity is low. You can cover the new concrete with water-saturated wet coverings of burlap or paper, or use plastic or construction paper coverings that are impervious to moisture. If you use liquid curing compounds that form a film impervious to moisture, apply such coatings immediately after the final finishing.