Placing Concrete in Cold Weather – An Overview


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.