Improved Corrosion Inspection Procedures for Reinforced Concrete Bridges: Electrical Resistivity of Concrete
PI: O. Burkan Isgor (OSU), burkan.isgor@oregonstate.edu
Dates: 07/01/2013 – 7/31/2015
Final Project Report: PacTrans-50-OSU-Isgor
First-level inspection procedures (e.g. visual inspection, chain drag or hammer sound tests) to detect corrosion-related issues in reinforced concrete bridges work only after significant damage to the structure has already occurred in the form of excessive cracking and/or delamination. Early detection and accurate monitoring of corrosion activity require more detailed inspections, which may include half-cell potential mapping and/or taking cores for laboratory analyses for mechanical properties and chloride profiling. Half-cell potential mapping of reinforced concrete bridges is a standardized method that indicates the probability of corrosion across the inspected areas. Half-cell potential results, however, do not provide any information about the rate of corrosion. It has also been shown that half-cell potential readings can be misleading, particularly in the case of localized corrosion, for which corrosion rates can be significantly high while measured half-cell potentials on concrete surface may indicate low probability of corrosion . As a result, corrosion monitoring that only relies on half-cell potential mapping can lead to misleading interpretations about the corrosion state of reinforced concrete bridges. Without the kinetic data, it is generally difficult to detect issues in early stages and to plan and prioritize mitigation and repair actions accurately. For a more robust assessment, additional data that would reflect the kinetics of the corrosion process are needed to supplement the half-cell potential mapping results. Unfortunately existing corrosion rate measurement techniques for concrete structures are inaccurate, unreliable and slow. Chloride profiling results alone cannot be used to assess corrosion rates within a bridge because they only provide information about when the steel may lose its passivity.
