Will the ground concrete freeze when the temperature drops below zero for 24 hours?

After 24 hours of concrete pouring, the temperature will drop below zero, and it will take 3-7 days for concrete to reach 50%-70% strength in low temperature weather.

If the concrete is attacked by negative temperature during the setting process, the hydration of cement is hindered, and the free water in it begins to freeze, and the volume increases by 9%, which is in danger of freezing and cracking concrete, seriously affecting the quality of concrete. After the concrete is first frozen and then cured at room temperature, its strength can still be increased, but it cannot be restored to the unfrozen level; And the earlier it is frozen, the more difficult it is to recover the later strength.

Extended data:

It is the key to ensure the quality of concrete construction in winter to adopt appropriate maintenance methods to prevent early freezing. In general, it should be selected according to the temperature, structural characteristics and site energy conditions.

(1) When the lowest temperature is not lower than-15℃ and the surface area coefficient of the structure (the ratio of surface area to volume) is not greater than 5, the heat storage method should be adopted;

(2) If the structural surface coefficient is above 5, there are early strength requirements and the power supply conditions are good, the electrothermal method can be used;

(3) When the surface coefficient of the structure is large, such as columns, beams and plates. , and there is enough steam available, you can use the steam method.

In addition, for precast concrete member joints, wallboard joints and cast-in-place ring beams, far infrared rays or electromagnetic induction heating can also be used to achieve early strength effect. No matter what kind of maintenance method is adopted, we should pay attention to the adaptability of the cement used, carry out thermal calculation, strengthen heat preservation and windproof, control the heating, constant temperature and cooling speed of artificial heating to avoid concrete freezing or cracking.

Baidu Encyclopedia-Winter Construction