Long term effect of chloride and sulfates concentration, and cation allied with sulfates on corrosion performance of steel-reinforced in concrete

Abstract

The occurrence of quick weakening of reinforced concrete due to chloride (Cl−) and sulfate (SO42-) ions is a serious concern now a day. The existence of SO42− ions and allied cation types in chloride solutions altered the chloride-generated corrosion behavior of reinforced concrete and it is still unclear what effect SO42- ions and allied cations types have on the chloride-generated corrosion behavior of reinforced concrete. For this purpose, the study has been conducted to assess the corrosion of surrounded rebar in concrete exposed to Cl− and combined Cl− and SO42- solutions allied with sodium (Na+) and magnesium (Mg2+) cation with low and higher concentrations of Cl− and SO42- ions till 27 months of exposure. The results reveal that the existence of SO42- ions in corrosive solutions retard the ingress of Cl− ions, and result in less rebar surface chloride (Crs) content and this effect is governing in the case of SO42- ions allied with Na + cation as compared to Mg2+ cation. The existence of SO42- ions allied with Na+ cation enhanced the corrosion activity. The ordinary Portland cement concrete (OPC–C), ordinary Portland cement with 20% fly ash concrete (O20FA-C) and Portland pozzolana cement concrete (PPC–C) exhibited an average of 1.86, 1.87, and 1.34 times respectively higher Icorr when exposed to composite solutions containing sulfate allied with Na + cation as compared to Mg2+ cation. The corrosion current density increased with an increase in the concentration of sodium sulfate in composite solutions however the opposite variation is observed for magnesium sulfate. The PPC-C showed excellent performance against corrosion of surrounded rebar as compared to O20FA-C followed by the OPC-C. The developed empirical model between Crs and Icorr from OPC-C and PPC-C predicted well Icorr values for O20FA-C.