In Situ Measurement of Cl~(-) Concentrations and pH at the Reinforcing Steel/Concrete Interface by Combination Sensors

摘要

This paper presents an in situ, nondestructive method of monitoring Cl~(-) concentrations and pH values at the steel/concrete interface. The Ag/AgCl electrodes prepared by the electrochemical anodization and the Ir/IrO_(2) electrodes prepared by thermal oxidation in carbonate served as Cl~(-) concentration and pH sensors, respectively. The potentiometric response of the Ag/AgCl electrode to the logarithm of Cl~(-) concentrations ranging from 1 X 10~(-4) to 2 M in saturated Ca(OH)_(2) solution simulating the inner electrolytic medium of concrete shows good linearity. The Ir/IrO_(2) electrode also exhibits an ideal Nernstian response in the range of pH 1-14. The Ag/AgCl and Ir/IrO_(2) electrodes were combined into a multiplex Cl~(-)/pH sensor, and the sensor was embedded in concrete close to the steel/concrete interface to realize an in situ and long-term measurement of Cl~(-) concentrations and pH values. The results indicate that the combined sensor is robust and sensitive enough to in situ measure Cl~(-) concentrations and pH quantitatively at the steel/concrete interface, which is of indispensable importance to the study of corrosion and protection of the steel in concrete.