PCE water reducing agent has its own antifreeze performance
In some cases, PCE water reducing agent has its own antifreeze performance without compounding: the PCE water reducing agent synthesized by partially replacing acrylic acid with itaconic acid (1:1 substitution) can withstand a negative temperature environment of about -5 degrees Celsius. The solution containing PCE 0.2% (dry basis) can not freeze at -5 degrees Celsius. However, it is mainly the dilute solution of admixture with low PCE content and low solid content that starts to freeze at close to 0 degrees Celsius. Adding enough early strength agent and a small amount of antifreeze agent can prevent the water reducer itself in a wide low temperature range. Freeze, and at the same time have the frost damage of antifreeze concrete at about -5 degrees Celsius.
PCE is a high-efficiency air-entraining water-reducing agent
Since PCE is a high-efficiency air-entraining water-reducing agent, it can be mixed with an early-strength agent and an appropriate amount of antifreeze. When necessary, a viscosity-changing agent and a coagulant should be added. The main antifreeze chemical components are sodium nitrite, calcium nitrite, potassium nitrite, sodium nitrate, calcium nitrate, potassium nitrate, sulfate, sodium chloride, calcium chloride, ammonia, urea and methanol, etc.
3 types of component should not be used as an antifreeze for PCE water reducing agents However, sodium nitrite should not be used as an antifreeze for PCE water reducing agents. Sodium nitrite is a secondary oxidant. When contacted with weakly acidic PCE solution, a redox reaction occurs and nitrogen oxide is released. When contacted with air, it is oxidized to NO2 gas, which is dark yellow and toxic, and the antifreeze performance will no longer exist. Similarly, potassium nitrite should not be used as an antifreeze component. The decomposition reaction can be alleviated by first diluting the nitrite with a large amount of water. Ammonia and urea are generally not used as antifreeze components for PCE. First, they are prohibited to be used as antifreeze components in indoor buildings. Second, they have retardation properties for concrete, which prolongs the initial setting time of standard PCE. Chloride is generally not used in PCE. First, it is easy to corrode steel bars and cannot use sodium nitrite to prevent rust at the same time. Second, the chloride salt solution will cause delamination after standing in the PCE solution.