Optimized retrieval of 1D-resistivity profiles in cover concrete by electrical sounding measurements

Abstract Geophysical techniques offer assessing conditions of reinforced concrete structures without invasiveness issues. Electrical Resistivity methods are promising tools for evaluating parameters such as water and ionic contents of concrete in reinforced concrete structures. In order to obtain water content profiles due to water ingress, the actual challenge consists in evaluating the 1D-resistivity profile with depth in concrete. To reach this goal, 1D-inversion procedures improving the extraction of true resistivity profiles in concrete are proposed. The first procedure, considered more conventional, is based on a discrete parameterization of the medium with three parameters. The second procedure is based on a continuous parameterization function defined with four parameters. We invert synthetic profiles to test the procedures and we study the effect of data noise on the inversion results. At last, an experimental validation on concrete slabs is carried out by comparing four different saturation degree profiles extracted from measurements or obtained by reference measurements. Results show that the continuous parameterization is able to accurately retrieve several profiles but that the resolution of the resistivity profile is limited by the maximum inter electrode spacing.