Reinforcement corrosion due to chloride-sulfate contamination and carbonation

The effect of chloride and sulfate contamination in concrete and its carbonation on reinforcement corrosion was investigated. Reinforced concrete specimens were contaminated with chloride and sulfate salts and exposed to an accelerated carbonation environment. Reinforcement corrosion was monitored by measuring corrosion potentials and corrosion current density using DC linear polarization and AC impedance spectrophotometric techniques. Results indicated that the corrosion current density on steel in the contaminated concrete specimens was more than that on steel in the uncontaminated concrete specimens. The corrosion current density on steel in the uncontaminated concrete specimens exposed to CO₂ was on an average three times that in the concrete specimens exposed to similar temperature and humidity but no CO₂. The increase in the corrosion current density in the contaminated concrete specimens, due to CO₂ exposure, was 1.2 to 2 times that in the similar concrete specimens not exposed to CO₂. Therefore, concrete structures exposed to carbonation environments should be protected by minimizing chloride and sulfate contamination and applying a protective coating.