Formulation of a Nondestructive Technique for Evaluating Steel Corrosion in Concrete Structures

This paper reports on a fundamental study on the formulation of a corrosion evaluation system for reinforced concrete structures based on a completely nondestructive technique. This is a method of evaluating the polarization resistance produced at the boundary between concrete and steel, without destroying the concrete surface, to estimate the resulting corrosion current density. A method of estimating the resistivity distribution within concrete to examine the steel corrosion environment is also proposed. This system consists of an equivalent circuit, a resistivity model for examining the effect of concrete, i.e., the measurement medium, and an actual measurement system. The equivalent circuit takes account of the electrode arrangement for resistivity measurement, and the impedance within concrete. This technique was verified by tests using specimens with controlled corrosion losses and was proven to express corrosion deterioration within concrete well. Evaluation by this technique was thus found feasible.