Investigation and modelling of the impact of reinforcement diameter in concrete on shapes of impedance spectra

Abstract

The impedance test results of the steel reinforcement of various diameters, which was passivated and corroded in concrete specimens, were analysed. The impedance plots clearly indicated the tendencies for spectra shapes of steel rebars to change depending on their diameters. A 3-dimensional model of steel-concrete system was developed to explain the observed effect. This system was composed of the identical electrical equivalent circuits connected in parallel. Each equivalent scheme was characteristic for a theoretical conductive path during the measurement, which was defined between a counter-electrode and the reinforcement. This model was used with the rectangular counter electrode to simulate the formation of impedance spectra characteristic for a single reinforcing bar with the concrete cover of any thickness, a variable diameter and a variable polarization area. The simulation modelling the impact of various reinforcement diameters verified the tendencies for impedance spectra of steel in concrete to change their shapes. The improved of fitting quality of the model spectra to the experimental ones were obtained by considering in that model the moisture content in concrete.