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When concreting in cold weather, heated concrete has a ‘flying start’ in the race for early strength, provided that the heat is retained. Either the aggregates or the water (or both) can be heated. Steam lances or steam coils can be used to heat aggregates and steam coils to heat the mixing water.
As a rough guide, heating the aggregates to 300C will contribute about 150C to the temperature of the mixed concrete, while heating the water to the same level will contribute about 80C. In these circumstances the temperature of the mixed concrete will be about 230C. Higher temperatures will increase the temperature of the concrete pro rata. When deciding the required mix temperature, an allowance must be made for cooling between mixing and placing. For site mixing and allowance of 5-100C might be appropriate, whereas for ready-mixed concrete it might be 10-150C. In practice, a ready-mixed concrete plant manager will usually advise the maximum mix temperature achievable in given weather conditions and an allowance for cooling must be deducted. This should be checked by trials before the weather becomes too severe.
Acknowledgement: Taywood Engineering
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