Pouring Concrete When It's Cold
WHY IS COLD WEATHER A PROBLEM?
There are two problems with pouring concrete in cold temperatures:
- Concrete can freeze before it gains strength which breaks down the chemical balance
- Concrete sets much slower when it is cold—below 50°F it sets very slow; below 40°F the hydration reaction stops entirely and the concrete will not gain strength.
Though concrete blankets offer the R-factor, or thermal resistance, needed to keep concrete from freezing in low temperatures, what challenges do they present?
These are not air temperatures, they are concrete temperatures. So when it’s cold, the concrete needs to be protected, until it can handle the cold on its own. The rule of thumb is that concrete is okay, once it has gained strength to about 500 psi. Almost simultaneously, the time that the concrete achieves 500 psi compressive strength, hydration of the cement has consumed enough of the water in the original mix so that there’s not enough water left in the pores to damage the concrete, even if it does freeze at that point. With most concrete, even at 50°, this occurs on day two. The first 24 hours are crucial to the curing and strength of the concrete, especially in cold temperatures.
There are two things we can do in cold weather to help the concrete reach 500 psi strength, change the mix to get it to set more quickly or PROTECT THE CONCRETE FROM THE COLD!
COLD WEATHER PROTECTION
While cold weather does have an effect on newly placed concrete, concrete work can continue late into the season with proper planning, sealing, and curing.
After concrete has been poured and set, curing begins. Proper curing ensures maximum concrete strength, durability, and crack resistance. The longer concrete cures, the stronger it becomes.
Even mildly cold temperatures can affect concrete curing time. At 50 degrees, for example, it takes nearly twice as long to cure the same concrete project that would take three days to cure at 70 degrees. Once temperatures reach freezing or below, concrete curing time is significantly longer and concrete may even freeze due to water expanding and contracting. This can cause fracturing of the concrete, and loss of its structural integrity.
Cold weather protection of newly poured concrete is critical — and concrete protection is not only recommended, but entirely necessary. Conventionally, concrete contractors have used concrete curing blankets to provide warmth to the concrete against the harsh elements in cold weather. They work by holding in heat and keeping cold out. This method of insulating concrete has been a viable alternative to adjusting the cement/water ratio or using a heating source in an enclosed work area. (Neither of those options are desirable, and carry many other challenges and obstacles in solving the cold weather conundrum).
THE STATE-OF-THE-ART ANSWER TO FREEZING TEMPERATURES
SingleSeal Freeze Protect™ is an easy-to-use product that can be used to seal & protect any clean concrete surface down to -20 degrees Fahrenheit. It applies easily, is safe to use both indoors and outdoors, and is invisible to concrete surfaces -- with no peeling, yellowing, or discoloration of the surface. With SingleSeal Freeze Protect™, your concrete is protected by a moisture-proof vapor barrier that will help prevent spalling damage, mold growth and that ugly white powder, efflorescence. It will also help your concrete to resist stains, and will reduce ice bonding, making the surface easier to shovel in snowy, cold weather.
Our complete product line is available to homeowners, contractors, and distributors worldwide! Protect concrete, brick, stucco, pavers and more, with our revolutionary sealers. In below freezing temperatures this Winter, you will continue to be productive with Professional Products Direct.