In winter concrete engineering construction, in order to prevent the concrete from freezing damage, antifreeze is often added to reduce the freezing point temperature of liquid water in the concrete and ensure that there is liquid water inside the concrete to satisfy hydration. exists to reduce damage caused by low temperatures. Most of the currently widely used antifreezes are composite antifreezes, which have the advantages of small slump loss, high water reduction rate, high early strength, and moderate setting time. Its main components include the following.
(1) Antifreeze component
Its function is to destroy the crystal form of ice and reduce the liquid content of water. Phase freezing point, maintain the liquid water required for cement hydration reaction inside the concrete, avoid concrete suffering from freezing damage, and reach early strength as soon as possible. The use of antifreeze components can first lower the freezing point of water and ensure that the hydration reaction of concrete continues at negative temperatures, such as sodium chloride, sodium nitrite, etc.; secondly, it can also change the lattice shape of ice and reduce frost heave stress. , to avoid damage to concrete strength, such as urea, methanol, etc. In addition, although some antifreeze agents cannot reduce the freezing point of water in concrete, they can directly react with cement to accelerate the setting and hardening of concrete and improve the early strength of concrete, such as calcium chloride, potassium carbonate, etc.
(2) Early strength component
Early strength component plays a role in the hydration reaction of concrete. The catalytic effect accelerates the setting and hardening of concrete, making it reach the critical frost resistance strength as soon as possible and improving the frost resistance of concrete. At the same time, due to the progress of the cement hydration reaction, the generation of bound water is promoted. The hydration reaction can also generate a certain amount of hydration heat to reduce the freezing damage of concrete.
(3) Water-reducing component
Reduce the water consumption of concrete and eliminate the internal causes of frost heaving. Enhance concrete density. Water reducing agent can disperse cement into smaller particles and improve the internal pore structure of concrete. The water-reducing agent adsorbed on the surface of the cement can release the wrapped water, making the ice crystal size from large to small, reducing the freezing pressure on the concrete when it freezes.
(4) Air-entraining component
The air-entraining agent is an introduced small bubble that absorbs ice crystals The frost heave stress generated during the formation process can reduce the crack expansion during concrete frost heave and reduce the frost heave force on concrete. The increase in air content can also increase the internal lubricity of concrete, improve the workability of concrete, and thereby improve the internal structure of concrete. Small bubbles can cut harmful pores in concrete and improve the durability of concrete.
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