As reliable and easy to use as ready mix concrete is, pouring it in cold weather can pose unique challenges. Extremely low temperatures can cause the water in the mix to freeze and expand, potentially causing the concrete to crack and weaken. If you find yourself with no other option but to pour in cold weather, fear not! Here are some tips to ensure your ready mix concrete pours smoothly, stays strong, and achieves optimum strength and durability.
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Create the ideal temperature for pouring. The best time to pour ready mix concrete in cold weather is during the milder part of the day, usually above 5°C (40°F). If the forecast is below freezing, plan to pour during the warmest hours of the day when the temperature spikes. Proper heating should be considered, and a temperature range of 10°C – 15°C (50°F – 60°F) is ideal for pouring the concrete. If using concrete blankets, make sure you’re getting enough coverage to warm the mix.
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Use warm ingredients. Cold weather can reduce the temperature of your ready mix concrete. To prepare for this, make sure to order warm aggregates and sand or store them in a warm space before using them to mix the concrete. Additionally, warm the water, cement, and any admixtures before pouring. Keep in mind that adding hot water to the ready mix can produce cracks.
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Adjust the mix design. To cater to the cold weather, using portland cement in the mix instead of blended cement can help prevent the concrete from freezing up. Adding more cement is also an option if you don’t want to limit the cold-weather usage of your concrete. If you need the mix to set quickly, using a warmer water temperature will speed up the setting time.
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Keep the thickness in check. Keep the pour thickness of your concrete to a minimum of 4 inches but ensure that the thickness is consistent throughout the job site. The thicker the pour, the more time it takes for the concrete to set, and the more likely it is to be affected by low temperatures. If you have concerns about the cold weather accommodating the thickness of your pour, consider using an accelerator or a steam curing system to speed up the hardening process.
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Cover and protect your concrete. Avoid pouring concrete in freezing, rainy or snowy conditions. Snow and rain droplets can reduce the surface tension of the concrete and can also cause surface depressions in the concrete. After pouring, cover the concrete with insulating blankets immediately to retain the warmth in the mix. Letting the concrete freeze over and then thaw can lead to a weakened surface layer. Always be prepared with tarps and other protectors, as these are essential when pouring in cold weather.
Conclusion: When pouring ready mix concrete in cold weather, the best defense is preparation and diligence. The temperature, materials, and mix design are all critical factors that must be well-considered to ensure that the concrete sets up properly and achieves the required strength and durability. Despite the challenges that come with pouring in cold climates, careful planning and execution will ensure that your project is a success.
