Facts have shown that low or negative temperature environments are very unfavorable to cement concrete construction. Low ambient temperature will slow down the hydration reaction of cement, thus affecting the growth of cement concrete strength. According to the test, every time the ambient temperature decreases by 1°C, the hydration of cement decreases by about 5% to 7%. In the range of 1 to 0°C, the hydration activity of cement decreases drastically and the hydration is slow. Generally, when the ambient temperature is lower than -3℃, free water will begin to freeze. When the temperature reaches about -10℃, the free water will almost freeze into ice, causing the hydration and hardening of cement to completely stop, thus greatly affecting the performance of concrete. .
When water is converted into solid ice, its volume increases by about 9%, causing internal stress in the cement concrete, causing the relative displacement of the aggregate and cement particles and the migration of internal moisture to the negative temperature surface. The formation of ice aggregates in cement concrete causes local structural damage. The density of water is high at 4°C. When the temperature drops below 4°C, the volume of water actually begins to expand, which will cause damage to the newly formed cement hydrate structure of fresh cement concrete. Experiments show that premature freezing of newly poured cement concrete will greatly reduce the ultimate strength, and the strength loss rate may reach 50% of the design mark, and even cause damage to the overall structure. However, when the cement concrete reaches the critical strength and suffers freezing, the ultimate strength loss of the cement concrete will be small, and the overall structural damage will not occur.
Therefore, during low-temperature construction in winter, a certain amount of cement concrete antifreeze can be mixed into the concrete to keep the cement concrete in a sufficient liquid phase at negative temperatures so that the hydration of the cement can continue. When the ambient temperature turns to a positive temperature, the strength of cement concrete can further increase and reach or exceed the design mark, thus effectively improving the performance of the concrete.
It can be seen that cement concrete antifreeze plays an extremely important role in winter construction.
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