General Guidelines for Durable Concrete in Cold Climates

Cracked concrete wallHere 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.

Heat curing concrete methods

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.

For more about concrete curing solutions, click here.

Placing Concrete in Cold Weather – An Overview

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Placing Concrete in Cold Weather - An OverviewThe performance of many building and remodeling materials is deeply rooted in basic chemistry and physics. Concrete seems like a simple product… but in reality it’s a highly sophisticated chemical compound. Due to its sophistication, care must be taken in its application to ensure proper curing and strength.

Hard, gray Jell-O

In some ways concrete is like Jell-O. You take a powdered mixture, mix it with water, stir it up, and before long you have a semi-solid compound.

There is a difference, however, between concrete and Jell-O. The cold temperatures in your refrigerator speed up the transition of the liquid mixture into a semi-solid material. With concrete, cold temperatures slow this transition. In the case of concrete, cold temperatures can be disastrous.

Crystals in Concrete

Concrete is a strong material because of its chemistry. When you mix water with the cement powder, you start an irreversible chemical reaction. Tiny crystals begin to grow. These crystals attach to one another, the sand and the gravel in the mixture. When everything goes right, you’ve created a compound hard as rock.

When water freezes it also turns into ice crystals. This transition would normally be no problem, but as the ice forms the volume of the water grows by nine percent. (That’s why ice cubes end up larger than the volume of water that produced them.) The ice tends to push or break things that get in its way.

In the case of freshly poured concrete, ice can destroy your slab. Enough cement crystals must be allowed to grow within the concrete to withstand the forces of growing ice crystals. Depending on the outside temperature, it can be a race against time. Most concrete chemists and engineers agree that if the concrete can attain a minimum strength of 500 pounds per square inch (PSI), it can resist ice damage.

Hot Stuff

The chemical reaction of concrete formation creates heat. This heat can be trapped by the use of insulating blankets. But if it’s cold enough, insulating blankets won’t keep the temperature at an optimum level for maximum curing efficiency. No insulating blanket will keep concrete at a temperature between 65 – 85°F, the optimum temperature range for proper concrete curing.

To ensure the concrete maintains the optimum temperature range, use Powerblanket® concrete curing blankets. Powerblanket® concrete curing blankets are heated blankets that not only insulate the concrete, holding in heat it naturally produces as it forms, but they also produce additional heat to keep the concrete within the desired temperature range.

Temperature is one of the most influential factors in determining the strength of concrete. For more information on that subject, click here.