The main components of concrete are cement, admixtures, coarse and fine aggregates, water, and additives.
In the mixing of cement and concrete, the main component of cement is CaO.
After hydration, Ca (OH) 2 is generated.
The carbonation of concrete refers to the chemical reaction between Ca (OH) 2 in concrete and CO2 in the air.
CO2 gas in the air penetrates into the concrete and reacts with alkaline substances to produce carbonate and water.
The process of reducing the alkalinity of concrete is called concrete carbonation, also known as neutralization.
Its chemical reaction is: Ca (OH) 2+CO2=CaCO3+H2O, producing neutral carbonate CaCO3.
Unbaked concrete is alkaline, and the minimum (critical) alkalinity for steel bars in concrete to remain passive is a pH value of 11.
5.
Carbonized concrete has a pH value of 8.
5-9.
5, indicating that carbonation reduces the alkalinity of concrete.
.