Carbonation of Concrete

Carbonation refers to the process where concrete reacts to the carbon dioxide present in the atmosphere.

Carbon dioxide permeates into the concrete, and under moisture it becomes dilute carbonic acid.

This process reduces the concentration of calcium hydroxide in concrete and convert it into calcium carbonate.

Such conversion lowers the pH value of pore water in hardened concrete and reduces the alkalinity of concrete.

The reduction of alkalinity removes the passivating layer that protects reinforcement from reacting with oxygen and water. It is more likely for reinforcement to corrode under this condition.