Impact of compressive fatigue on chloride diffusion coefficient in OPC concrete: An analysis using EIS method

•Electrochemical impedance spectroscopy is applied to evaluate concrete’s fatigue damage.•An electrical equivalent circuit is proposed to extract parameters from impedance spectra.•An indicator (IDF, 1/RCCP+1/RCP) is adopted to quantify the fatigue damage level.•Relationships between chloride diffusion coefficients and IDF are finally estimated. Fatigue damage is one of the most important factors impacting the chloride diffusion coefficient in concrete. In this paper, the electrical impedance spectra (EIS) method is used to analyze the damage level of the fatigue concrete. An electrical equivalent circuit is established to extract the electrochemical parameters from the impedance spectra. It is shown that the fitting results of the equivalent circuit match well with the experimental spectra. By analyzing the physical meanings of the parameters, the reciprocal of the overall resistance (1/RCDP+1/RCCP) is finally adopted as an indicator of the fatigue damage level. Chloride diffusion coefficients of concrete undergoing fatigue damage were determined by a modified RCM method. It is found that the chloride diffusion coefficients decrease linearly with the overall resistances. The reduction in DRCM is found to be rapid for the high w/c ratio (w/c 0.5) concrete and gradual for the low w/c ratio (w/c 0.36) concrete. It is also found that DRCM increases nonlinearly with the indicator IDF. The increasing rates get smaller when IDF grows, and DRCM has a maximum value when IDF trends to infinity.