Potentiometric response of chloride sensors in cementitious materials of varying chemical composition and water-to-cement ratio

摘要

Free chloride ions are the main cause of steel corrosion in reinforced concrete structures. Ag/AgCl electrodes, as chloride sensors, are predominantly sensitive to chloride ions and respond electrochemically to the chloride ion activity in the environment. This is reflected by changes of the open circuit potential (OCP) of the sensors. To investigate the effect of the cement-based matrix on OCP readings, this paper presents the electrochemical responses of chloride sensors, embedded in cement paste specimens of hydrated pure cement phases of different water-to-binder ratios. The specimens were immersed in alkaline solutions with various chloride concentrations. The results show dependency of the OCP of the sensor on the surrounding hydrated cement-based matrix. This effect was more pronounced when the specimens were immersed in solutions of lower chloride concentration. In contrast, these effects were negligible at high (> 500 mM) chloride concentrations.