One of the main causes of premature deterioration of concrete structures is the corrosion of steel reinforcement. Corrosion is mainly caused by the ingress of chloride ions into concrete. The Rapid Chloride Permeability Test (RCPT) has been developed as a quick test able to measure or predict the rate of transport of chloride ions in concrete. The goal of the research presented here was to study the microstructural changes induced by the RCPT using impedance spectroscopy (IS) measurements. Test series included one- and-a-half year-old materials: (1) paste, (2) mortar, (3) normal strength concrete (NSC) and (4) high strength concrete (HSC). IS was used to investigate the effect of high electric fields, increased temperatures due to the RCPT, as well as the impact of RCPT sample preparation on the microstructure and transport properties of the materials tested. 2-point electrode-configuration measurements were taken before and after RCPT for all the materials tested. Experimental results showed that paste and mortar exhibited large changes in electric resistance as a result of RCPT, whereas NSC and HSC presented moderate changes. As electrical properties of the HSC were affected by RCPT sample preparation, this material required additional analysis. 4-point electrode-configuration and 4-point direct current resistance were measured for HSC. Based on this study it is suggested that deionized water treatment induces layering (low conductivity surface layers). Using the theoretical correlation between initial current and total charge measured during the RCPT, resistance/conductivity measurements can be used to assess RCPT performance and resistance measurements can replace the RCPT.