Modeling and Interpretation of Responses of Concretes in Four‐Probe Impedance Measurements

Abstract

Typically, a detailed non‐destructive characterization and quality assessment of concretes under “real‐world”, for example, road conditions, are complicated. Impedance spectroscopy is a powerful technique for obtaining insights into concrete property changes during its usage in various environments. However, interpreting and analyzing impedance responses can be challenging due to the lack of explicit physical impedance models of different concretes. In this work, we have elaborated and verified such a model for the so‐called four‐electrode impedance measurements for dry materials and concrete exposed to aqueous K2SO4 solutions, which can cause concrete corrosion. A differential impedance analysis, which does not use any preliminary model assumption, suggested the elements′ presence originating from different types of pores and the contribution of the grain boundary capacitance. Based on this information, the equivalent circuit model was constructed using rules typical in solid‐state ionics and verified by fitting the impedance data to the model; and its parameter changes after adding the K2SO4 solutions were analyzed. The model demonstrated excellent agreement with the measured spectra. Its parameter changes generally agree with the expected behavior of the concrete samples in the corrosive environment. Possible applications of such impedance analysis are briefly discussed.