The Application of Indirect Impedance to Monitor Corrosion Rates of Inhibitor-Impregnated External Post-Tensioned Tendons

Abstract

An indirect electrochemical impedance spectroscopy method was previously explored as a potential nondestructive method for detecting corrosion of steel in post-tensioned tendons which are used as reinforcing structural elements in segmental bridge construction. The tendons are composed of a grout-filled cylindrical plastic duct that contains high-strength steel strands. A proof of concept was demonstrated by experiments performed on tendons with passive and corroded strands and through finite-element simulations of the indirect impedance response.1 Further work showed that the indirect impedance method was sensitive to local corrosion in field tendons if the measurement is obtained near the corroding region.2 This work expands the application of the indirect impedance methodto corrosion monitoring of inhibitor-impregnated post-tensioned tendon sections. A corrosion inhibitor that is injected into the tendons through the interstitial space of the strands may be capable of preventing or stopping corrosion. The sensitivity of indirect impedance measurements to changes in both electrical properties of the grout and the corrosion rate of the steel is assessed by comparison to traditional measurements of the impedance in which direct contact is made to the steel. Additionally, further assessment of the indirect impedance method is made by relating the analysis results to the actual corrosion damage obtained by autopsies of the tendon sections. C. L. Alexander and M. E. Orazem. "Indirect Impedance for Corrosion Detection of External Post-tensioned Tendons: 2. Multiple Steel Strands." Corrosion Science 164 (2020): 108330.C. L. Alexander and M. E. Orazem. "Indirect electrochemical impedance spectroscopy for corrosion detection in external post-tensioned tendons: 1. Proof of concept." Corrosion Science164 (2020): 108331.