5 quick tips from JP!
When placing concrete at temperatures below 5°C, you need to take a few precautions.
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Make sure the formwork and the surface you are pouring onto are free from snow and ice. Do not place concrete against frozen surfaces.
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Order warm concrete, up to 25°C!
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Remember that a curing compound is just as important in winter as it is in summer. Make sure to use one fit for winter.
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Cover the concrete as soon as possible. Remember that wind has a significant effect!
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Consult a concrete technologist about the use of admixtures and Antifreeze powder.
HARDENING TIME
Cold weather has a major impact on concrete. That is why we need to use admixtures when cold conditions set in.
When temperatures drop and we cannot prevent the concrete from freezing, we can add Antifreeze, an admixture that lowers the freezing point. It works on the same principle as antifreeze in a car. This prevents the water in the concrete from freezing, even at sub-zero temperatures. We can adjust the Antifreeze dosage for temperatures down to −15°C. As the water remains liquid, the cement and water can still react, but the reaction is extremely slow.
If B30 concrete hardens after 7 hours at 20°C, with the concrete, air and formwork all at 20°C, it takes 14 hours if everything is at 10°C. At 5°C, it takes 28 hours. And at −15°C, it takes 5,400 hours, or 7 months, before the concrete begins to harden. Luckily, we do not have temperatures of −15°C for 7 months here in Southern Norway! That is why we use admixtures and heat to adapt the concrete to the temperature conditions during placement.
We can also help you estimate this in advance using the HETT-22 software.
ACCELERATORS
A setting accelerator (SA) helps the concrete set throughout its full depth.
This helps reduce the risk of a firm surface forming over soft concrete underneath when pouring onto a cold base, as is often the case from November to March.
Remember: if your feet get cold when you stand barefoot on the gravel, the concrete will certainly get cold too!
The dosage is adjusted to suit the pour, up to 6 kg/m³.
For tall walls, where formwork pressure can be a challenge, one solution is to heat the concrete to 23–24°C and combine this with a setting accelerator to achieve rapid setting.
Remember to check that the concrete has the consistency you need before our drivers add SA to the mixer truck.
A hardening accelerator (Ultra) helps concrete develop strength faster in cold weather. It can make the difference between being able to remove the formwork the following day and having to wait an extra day. Ultra is the right solution when concrete placement takes some time, but your construction schedule leaves little time to wait for strength development.
In some cases, it may be necessary to combine both types of accelerator. This is typically when conditions are cold and you are pouring a thin section or a small volume of concrete. Contact us, and we will find a solution together.
Contact us
Winter can be a challenging time to pour concrete, but it does not have to be. We are happy to help you complete your project in any season, with a wide range of practical solutions at our disposal.
