Pouring Concrete in Cold Weather: Essential Guidelines
Despite common misconceptions, concrete can be poured, finished, and cured in any temperature—including freezing conditions. The key is implementing the right precautions to prevent it from freezing before it sets properly.
How Cold Weather Affects Concrete Curing
Concrete hardens through a chemical reaction, turning from liquid to solid over time. Lower temperatures slow down this process, meaning cold weather can significantly extend curing times. The biggest risk in winter is that fresh concrete freezes before it gains enough strength, which can lead to structural weaknesses.
What Happens If Concrete Freezes Too Soon?
If newly placed concrete freezes, the damage is instant and irreversible. Even if temperatures rise and curing continues, the initial freezing weakens the structure permanently. Research from the Portland Cement Association states that concrete freezing before reaching adequate strength can reduce compressive strength by up to 50%.
Best Practices for Pouring Concrete in Cold Weather
Before pouring, check the ground temperature, not just the air temperature. The surface might be frozen even if the air feels mild, and pouring concrete on frozen ground should always be avoided. To prevent this, use concrete blankets or black plastic sheeting to warm the area for a few days beforehand.
To combat freezing temperatures, you can:
Increase the cement content in the mix
Use heated water instead of cold in the mix
Warm the aggregates before mixing
Incorporate chemical accelerators (e.g., calcium chloride or non-chloride alternatives)
Utilize water reducers to minimize excess moisture and bleeding
Protecting Concrete During the Curing Process
Since the curing phase is when cold exposure can do the most harm, proper insulation is critical. Lower temperatures slow down setting times significantly:
A 10°C (18°F) drop in temperature can double the time it takes to set.
If a pour normally sets in six hours at 20°C (68°F), it may take 12 hours at 10°C (50°F) or 24 hours at -1°C (30°F).
To ensure strength and durability, concrete should be insulated for at least five days using blankets, straw, or plastic covers. Exposing it too soon can cause surface layers to freeze and break apart. Even if freezing doesn’t occur, an uncovered slab won’t be as strong as a well-protected one.
Managing Tilt-Up Construction in Cold Conditions
Cold weather slows down all construction, including tilt-up projects, where walls are poured and lifted on-site. To minimize delays, heaters should be used to maintain the right curing environment, allowing work to continue smoothly throughout winter.
By following these cold-weather concrete strategies, you can prevent structural issues, avoid costly setbacks, and keep projects moving—no matter how low the temperature drops.
January, 2025