Corrosion risk assessment of chloride-contaminated concrete structures using embeddable multi-cell sensor system

Monitoring the service condition of concrete structures requires the quantitative assessment of properties and corrosion rate of structural steels surrounded by concrete. A multi-cell sensor system that included a reference electrode, a chloride content sensor, a macrocell current unit and an electrical resistance measurement unit was developed. This system provided the following important electrochemical data in the cover-zone concrete on site: open circuit potential, macrocell current from anodes to cathode, chloride profile, concrete resistance and corrosion rate of built-in anodes. The experimental results show that the macrocell current increases when the chloride content in concrete is higher. Thus, monitoring the chloride content is a good method for monitoring the corrosion state. The chloride ion content and cover depth are the key factors that affect the electrical resistance of concrete. Without considering the temperature and time, a simplified model of the instantaneous corrosion rate of steel rebar in a concrete structure based on the measured chloride contents and concrete resistance was proposed. The test results further prove the reliability of this simplified predicting model.