Examining and Modelling the Influence of Lengths of Rebars in Concrete to Shapes of Impedance Spectra

A comparative analysis of the results of impedance tests of two series of concrete specimens with various lengths of reinforcement in a state of passivation and corrosion was conducted. Impedance plots were found in the clear trends in the shapes of impedance spectra of the reinforcement as a function of its length. With the aim of explaining the observed phenomena there was developed a model of the steelconcrete system with parallel-connected equivalent electrical circuits. The model allows the simulation of the formation of impedance spectra characterizing any length of reinforcement in concrete, using a counter electrode placed on the outer surface of the concrete cover. The model impedance spectra were obtained after taking into account two groups of electrochemical parameters characterizing, by analogy with experimental testing, reinforcing steel in a state of passivation and corrosion. The conducted model simulation of the influence of various lengths of reinforcement, assuming the total polarization of the areas, confirmed the observed trends in experimental studies of changes in impedance spectra shapes of reinforcing steel in concrete.