Effect of Combined Chloride-Sulfate Solutions and Associated Cation Types with Sulfate Ions on Corrosion Performance of Steel Rebar in Concrete

Abstract The rapid deterioration of reinforced concrete structures located in marine environment because of chloride-generated corrosion remains a matter of serious concern. The marine environment mainly comprises chloride (Cl−) ions, sodium (Na+) ions, sulfate (SO42−) ions, and magnesium (Mg2+) ions. The existence of SO42− ions with Cl− ions influences the chloride-generated corrosion behavior because of the binding of these ions with hydrated C3A in concrete. In this research, an experimental study has been conducted to assess the performance of embedded rebar (carbon steel) against corrosion in normal concrete subjected to chloride (NaCl) and combined chloride-sulfate (NaCl with MgSO4 and NaCl with Na2SO4) solutions for 27 months of exposure periods. The results showed that the corrosion performance of the embedded rebar was influenced by SO42− ions and its associated cation (Na+ and Mg2+) type. The SO42− ions associated with Na+ cation resulted in higher corrosion current density (Icorr) as compared to Mg2+ cation in the concomitant presence of Cl− ions. The presence of Cl− ions significantly increased the corrosion rate of steel rebar, whereas the presence of SO42− ions (irrespective of associated cation, i.e., Na+ and Mg2+) in the exposure solution hindered the effect of Cl− ions on increasing the corrosion rate of steel. The established empirical relationship obtained between half-cell potential (E0), and Icorr predicted well the Icorr values obtained from ordinary portland cement with 20 % fly ash concrete used in the present research work and with the results obtained by different researchers in the literature.