Embeddable combination probe for in-situ measuring Cl- and pH at the reinforcing steel/concrete interface

Abstract

Ag/AgCl electrodes and Ir/IrO2, electrodes were prepared by anodic electrochemical oxidation and thermal oxidation in carbonate and served as Cl- and pH probes, respectively. The potentiometric response of the Ag/AgCl electrode to the logarithm of Cl- concentrations ranging from I X 10(-4) to 2 mol/L in saturated Ca(OH)(2) solution trying to simulate the inner electrolytic medium of the concrete shows very good linearity, and the Ir/IrO2 electrode also shows an ideal Nernstian response between pH I and pH 14. The Ag/AgCl and Ir/IrO2 electrodes were combined into combination Cl-/pH probe, and the probe can be embedded in the concrete and measure Cl- contents and pH at the steel/concrete interface or in the concrete because of its satisfying mechanical property and long term stability of the potential readings depending on the Cl- concentration or pH. The results are of significance to study the influence of Cl- concentration and pH on the mechanism of reinforcement corrosion in concrete.