General Guidelines for Durable Concrete in Cold Climates
Here are some guidelines to follow for trouble-free concrete in cold climates:
Maintain a Low Water to Cement Ratio
The cement in concrete is the glue that holds everything together. The more water you add when you mix, the weaker the concrete will be for a given amount of cement. While adding water to concrete makes it easier to pour, it can also weaken the concrete.
Use No More than a Four Inch Slump
Slump refers to the stiffness of the mix. The lower the number the stiffer concrete is. Concrete can actually be mixed and poured with a one or two inch slump. Highway median crash barriers are frequently poured with a 1 or 2 inch slump. The resulting concrete is stiff enough to stand three to four feet tall within moments after pouring. It also becomes extremely strong once it’s cured. Have you seen highway median work where the crash barrier is done with a forming machine? The concrete is so stiff that it can stand four feet tall moments after it is poured – yet it attains a high strength once cured and dried.
Use a Six Bag or 4,000 PSI Mix
You must have enough cement in each cubic yard to make sure it is strong. For concrete exposed to freezing temperatures you’ll need a minimum of 6 bags (564 lbs) of cement per cubic yard, or mixture strength of 4,000 pounds per square inch. Diluting your mix will often result in weak and damaged concrete.
Use Air-Entrained Concrete
Special chemicals can be added to concrete as it is mixed. These chemicals create micro-air bubbles within concrete. The air spaces become shock absorbers as water freezes within concrete. Make sure you use air-entrained concrete in cold temperatures.
Create the Right Slope
Concrete slabs need to have good drainage. Slabs need a minimum slope of 1/4″ per linear foot to shed water. If water pools on the surface and freezes, the concrete can be damaged.
Provide Adequate Curing Conditions
If the temperature is too cold, the concrete may not have reached a minimum strength of 500 psi soon enough to resist the effects of freezing temperatures. If your concrete isn’t protected with Powerblanket™ concrete curing blankets after it’s poured, it may cool too rapidly, slowing the chemical reaction. Use concrete Powerblanket™ concrete curing blankets to maintain the optimal curing temperature of between 65 – 85°F.
Don’t Use Silicone Sealers
If you feel the need to seal your concrete, don’t use silicone sealers. Silicon sealers form a film. Use a breathable sealant or water repellent containing silanes or siloxanes.
Use a Heated Powerblanket
Powerblanket heated thawing and concrete curing blankets effectively remove frost from work sites and allow concrete to cure at optimal temperatures without risk of freezing or rapid drying.