Corrosion Inhibition by Cr-bearing Rebar in Concrete Due to Combined Deterioration of Carbonation and Chloride Attack

With the aim of developing Cr-bearing rebars having required resistance to deteriorative environments prone to carbonation with or without chloride attack, ten types of steel bars having different Cr contents were embedded in concretes with chloride ion contents of 0, 0.3, 0.6, 1.2, and 2.4 kg/m3 to fabricate specimens assuming such deteriorative environments. After being carbonated to the reinforcement level, these concretes were subjected to corrosion-accelerating cycles of heating/cooling and drying/wetting. The time-related changes in the corrosion area ratio and corrosion loss of the Cr-bearing rebars were then measured to investigate their corrosion resistance. The results revealed that the Cr content required for corrosion resistance in a simple carbonating environment was 5% or more. The corrosion-resisting performance of Cr-bearing rebar was particularly noticeable with a Cr content of 7% or more. In a deteriorative environment prone to both carbonation and chloride attack, corrosion resistance was evident with a Cr content of 7% or more and 9% or more in concretes with chloride ion contents of 1.2 and 2.4 kg/m3, respectively.