Does13oh after concrete pouring have an effect on-2 degrees?

1, natural conditions without any measures, concrete construction will stop below 0 degrees. Otherwise it will be frozen.

2. When antifreeze is added at -5℃,-10,-15℃, curing methods such as heat storage method or comprehensive heat storage method must be adopted to ensure that concrete does not freeze at-10,-15, and -20℃, and the concrete will continue to be cured until it reaches the critical freezing strength.

3. When the outdoor daily average temperature is steadily lower than 5℃ for five consecutive days, the winter construction starts and the winter temperature drops. In many areas, the temperature is below 0℃ (negative temperature), and the moisture contained in soil, concrete and mortar. Building materials are brittle due to freezing, which brings many difficulties to building construction. When the average temperature is lower than 5℃ or the daily minimum temperature is lower than -3℃ for five consecutive days, winter construction measures should be taken to ensure the engineering quality.

1 Several common freezing conditions of cast-in-place concrete

1. 1 cast-in-place concrete without any additives is frozen.

In the low temperature environment, the cast-in-place concrete without any admixture is frozen at 0 ~ 2℃. When the temperature is lower than 0℃, especially when the temperature drops below the freezing point of concrete (the freezing point of fresh concrete is -0.3 ~-0.5℃), the water in cast-in-place concrete begins to freeze. At this time, the volume expansion of frozen cast-in-place concrete is about 9%, and the strength loss is about 50% or more. Moreover, after the temperature returns to normal temperature, the strength of this frozen cast-in-place concrete without any additives will not recover. For more information, please pay attention to WeChat official account: Construction Engineering House.

1.2 cast-in-place concrete mixed with early strength agent is frozen.

In order to make the cast-in-place concrete reach the critical freezing strength of concrete as soon as possible during the low-temperature curing period (generally 3.5 ~ 7.0N/mm2), appropriate early strength agent is usually mixed into the cast-in-place concrete to promote the hardening of cement, so that the concrete has the early strength effect and prevent early freezing. However, adding early strength agent is only applicable to cast-in-place concrete with ambient temperature above -5℃. If the ambient temperature is below -5℃, cast-in-place concrete will freeze even if it is mixed with early strength agent, but the strength of concrete mixed with early strength agent will continue to increase after the temperature returns to positive temperature.

1.3 cast-in-place concrete mixed with antifreeze is frozen.

The adaptive temperature of cast-in-place concrete mixed with antifreeze is generally lower than that of fresh concrete mixed with early strength agent, and is limited by the design temperature of antifreeze, so winter construction can usually be carried out at 0 ~-20℃. However, the cast-in-place concrete mixed with antifreeze will also freeze and crack at negative temperature. For example, cast-in-place concrete mixed with low-temperature early-strength antifreeze will freeze and crack when the temperature is lower than-10℃. When the temperature is below-15℃, the strength loss of this cast-in-place concrete mixed with low temperature and early strength antifreeze is about 20% or more. Another example is cast-in-place concrete mixed with negative temperature antifreeze, which freezes when the ambient temperature is-15 ~-20℃. When frozen at -25℃ or lower, the strength loss of cast-in-place concrete mixed with negative temperature antifreeze can also reach more than 20%.

1.4 Due to the high internal temperature, the external surface of mass cast-in-place concrete freezes.

In low temperature environment, mass cast-in-place concrete generates heat due to cement hydration. It is easy to raise the internal temperature of cast-in-place concrete and accelerate the internal of cast-in-place concrete to reach the critical strength of freezing. However, the external surface of mass cast-in-place concrete is exposed to low temperature, and when the temperature drops in vain, it is easy to identify and deal with the early freezing of cast-in-place concrete with frozen surface.