How to Pour Concrete in a Cold Climate
Ideal conditions for working concrete seldom occur in the middle of winter, but if your foundation begins to crumble or your car threatens to disappear into a bottomless pothole in your driveway, you cannot put it off until summer. Employing a few tricks of the trade to work with concrete in the cold and still ensure a successful pour. Does this Spark an idea?
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Things You'll Need
- Heat lamp or space heater
- Insulated blankets
- "Tent" or temporary shelter
- Concrete
- Calcium chloride (optional)
- Plasticizing concrete additive (optional)
- Hot water
Instructions
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Check your local forecast. If it calls for temperatures lower than 40 degrees at any point during the length of time you will need to cure concrete (generally five to seven days minimum), or not above 50 degrees at least 12 hours in a row, thaw the ground before beginning work. According to Mineral Resources Technologies, "At 50 degrees Fahrenheit, the rate of hydration and strength gain is approximately half the rate of the same mixture at 73 degrees Fahrenheit."
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Clear snow if applicable, and set up a heat source over the area you wish to pour. Use a heat lamp or space heater for small areas---protected with a temporary "tent" or shelter to preserve the heat. For extremely large areas, such as a house slab, buy insulated blankets designed especially for the purpose. Placed directly on the ground, they quickly bring temperatures up to 65 degrees.
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Mix concrete using less water to decrease "slump." Since concrete will set slowly at low temperatures, use a minimal amount of water, which can freeze and lead to strength reduction.
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Add calcium chloride to the mix to accelerate the setting and curing if the site contains no bare reinforcing steel, or use a plasticizing additive to lower the water content of the mixture, thus aiding cure. Use hot water to mix the batch, as this will kick-start the set and allow insulated blankets to work more efficiently.
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Pour the concrete as quickly as possible to reduce heat loss.
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Place insulated blankets over wet concrete immediately upon completing the pour. Keep the concrete moist and at 50 degrees or higher for at least five days in order for concrete to achieve maximum strength. Above all, do not allow concrete to freeze, which will render it weak and prone to cracking. If necessary, set up a temporary structure over the pour and heat it with your space heater or heat lamp.
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Tips & Warnings
Allow extra cure time for concrete poured in cold weather before back-filling or adding weight of structures above.
