Concrete Pressures - Formwork
4) Temperature: The time it takes concrete to harden is influenced greatly by its temperature. The higher the temperature of the concrete, the quicker it will harden. Most formwork designs are based on an assumed average air and concrete temperature of 21°C. At low air temperatures, the hardening of concrete is delayed and you need to decrease your pour rate or heat your concrete to keep the pressure against the formwork from increasing. Ideally, concrete should be poured at temperatures between 16°C and 38°C. Outside this temperature range there is often insufficient moisture available for curing. If adequate water for curing is not available or freezes, the strength of the concrete will suffer.
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