Antifreeze has three characteristics according to its mode of action:
1) After being mixed with water, it has a very low co-dissolution temperature, which can lower the freezing point of water and allow concrete to still hydrate at negative temperatures. Such as sodium nitrite, sodium chloride. However, once the concrete freezes due to insufficient dosage or too low temperature, it will still cause freezing damage and reduce the final strength of the concrete.
2) It can not only lower the freezing point of water, but also seriously deform the lattice structure of ice containing this type of material, so it cannot form ice expansion stress and destroy water. Chemical mineral structures, such as urea and methanol, can damage the strength of concrete. When the dosage is insufficient, the strength of concrete stops growing at negative temperatures, but it has no effect on the final strength after turning to positive temperatures.
3) Although its aqueous solution has a very low co-dissolution temperature, it cannot significantly reduce the freezing point of water in concrete. Its function is to directly react with cement. Such as calcium chloride and potassium carbonate, which accelerate the setting and hardening of concrete through chemical reaction and are conducive to the development of concrete strength.
It should be noted here that antifreeze and antifreeze group are not the same concept. Antifreeze is a type of admixture, which consists of water-reducing components, antifreeze components, air-entraining components, and sometimes early-strength components. Its function is to not only harden the concrete at negative temperatures, but also enable it to eventually reach the quality level of concrete cured at normal temperature. The antifreeze component refers to a chemical substance that protects the concrete mixture from freezing damage in negative temperature environments.
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