corrosion of reinforcement bars

The expansion of the corrosion products (iron oxides e.g., Fe2O3) of carbon steel (iron) reinforcement structures may induce mechanical stress that can cause the formation of cracks and disrupt the concrete structure. If the rebars have been poorly installed and are located too close to the concrete surface in contact with the air, spalling can easily occur: flat fragments of concrete are detached from the concrete mass by the rebars corrosion and may fall down.