Monitoring chloride concentrations in concrete by means of Ag/AgCl ion-selective electrodes

This work investigates the applicability of Ag/AgCl ion-selective electrodes for the non-destructive measurement of chloride concentrations in concrete. Sensitivity to potential interfering ions and stability of the Ag/AgCl membrane in neutral and alkaline solu-tions are presented. The results indicate negligible interference by fluoride, sulfate, and hydroxide, but con-siderable interference by bromide and sulfide. In completely chloride-free alkaline solutions, the ion-selective electrodes are not stable over time, but they become again functional as soon as chlorides arrive at the sensor. It is concluded that the studied ion-selective electrodes are applicable for monitoring chloride concentra-tions in concrete structures exposed to chloride-bearing environments. The applicability in concrete contain-ing blast furnace slag or other sulfide sources is however questioned.