Understanding the Process of Corrosion in Reinforced Concrete
Corrosion is a natural process that occurs when the steel rebar within reinforced concrete structures rusts. In scientific terms, concrete corrosion is defined as the “destruction of metal by chemical, electrochemical, and electrolytic reactions within its environment.” It typically forms as the concrete ages
Why Is Concrete Corrosion a Problem?
Corrosion is initiated when materials that are harmful to steel, such as CO2 and chloride from de-icing salt, start to penetrate concrete and reach the steel reinforcement. As an electrochemical reaction, electrons migrate from the anodic zone to the cathodic zone, releasing ferrous ions at the anode and hydroxide ions at the cathode. This will eventually lead to a potential difference between the anodic and cathodic areas at the surface of the steel reinforcement. This results in the creation of rust as a by product. Since rust occupies a larger volume than steel, it exerts internal pressure which causes the surrounding concrete to crack and become damaged. These cracks make their way to the surface of the concrete which causes even more CO2 and chloride to penetrate the concrete and speed up the process of corrosion.
Corrosion is responsible for up to 90% of damage to reinforced concrete structures.
-Ueli Angst, Professor, Institute for Building Materials