1. Sulfate attack
After contact with sulfate solution, calcium chloride has corrosive effect on concrete. Sulfate reacts with calcium ions and aluminum ions in the cement slurry to form calcium sulfate and calcium sulfoaluminate hydrates, causing concrete cracking. After calcium chloride is used, the resistance of concrete to sulfate attack will decrease.
2. Heat of Hydration
After using calcium chloride, the heat of hydration is generated faster and the hydration process is faster, especially in the first 10 to 12 hours. The total amount of hydration heat does not change much, but the rapid generation of hydration heat is helpful to concrete construction in winter.
3. Alkali-aggregate reaction
When high-alkali cement is used with certain types of aggregates, the aggregates will expand, causing concrete corrosion. Calcium chloride in concrete will aggravate the reaction between alkali and aggregate. If calcium chloride must be used, low-alkali cement, pozzolan cement or inactive aggregate can be used to control expansion.
4. Rebar corrosion
In concrete containing calcium chloride, a stable film that protects steel from the external environment cannot be effectively maintained, and there is a possibility of corrosion of steel bars.
It is not allowed to use calcium chloride in prestressed concrete, because the large surface area of the steel bar and the large stress difference will cause a large corrosion rate. It is not recommended to use calcium chloride in steam curing concrete.