Studies on corrosion monitoring of reinforced concrete in a chloride environment using an embedded solid-state reference electrode

•Corrosion of steel rebar embedded in various cover depth concrete was investigated.•MnO2-ESSRE was used for in-situ corrosion monitoring of the steel rebar by EIS.•The chloride diffusion coefficient was calculated using the non-destructive technique.•Relationships between corrosion current density and time to cracking were examined. In the present study, the corrosion status of steel rebars embedded in concrete with various cover thicknesses and exposed to conditions simulating a marine environment (3.5 % NaCl) was monitored by an embedded solid-state reference electrode (ESSRE). Electrochemical impedance spectroscopy (EIS) results confirm that corrosion initiation of the steel rebars occurred at 702, 1144, 1469 and 2454 h for C10, C15, C20 and C30 concrete specimens, respectively. Further, the relationship between the free and bound chlorides for C15, C20 and C30 specimens were defined by Temkin isotherm. In addition, the time to crack initiation was predicted by the El Maaddawy model. This study has successfully demonstrated that the solid-state MnO2 electrode is reliable for monitoring the onset of steel rebar corrosion in concrete by a non-destructive method.