Study On Electrochemical Impedance Spectroscopy Of Concrete In Chloride Environment

In this paper, Electrochemical Impedance Spectroscopy tests were made on concrete in chloride environment and by applying the software of Origin7.5and ZsimpWin to analyze the measured data, electrochemical impedance parameters of concrete were attained. The influence of water-cement ratio, chloride ions and mineral admixtures on concrete meso-structure was attained by the change of electrochemical impedance parameters. The results are as followed:(1) For ordinary concrete at period of hydration stability, in the case of same environment, with the decrease of water-cement ratio, the resistance of pore solution, resistance to transfer the hydrated electron, coefficient of diffusion impedance of concrete and phase angle index increase; hydraulic radius decreases; the electric double layer capacitor is substantially constant. That indicates in chloride environment, for concrete with lower water-cement ratio, extent of hydration was higher and the total porosity and mean pore size of concrete was lower; constant of phase angle index shows water-cement ratio had no obvious influence on the electrical property of C-S-H gel.(2) For concrete with mineral admixtures at period of hydration stability, in the case of same environment, with the increase of mineral admixture content, the resistance of pore solution, resistance to transfer the hydrated electron, coefficient of diffusion impedance of concrete and phase angle index increase; hydraulic radius decreases; the electric double layer capacitor is substantially constant. That indicates that the total porosity and mean pore size of concrete decreased and compaction of concrete enhanced by added mineral admixture, thereby the durability of concrete was improved; constant of phase angle index shows mineral admixtures had no obvious influence on the electrical property of C-S-H gel.(3) For concrete at period of hydration stability, in the case of same parameters, the impedance parameters, such as resistance of pore solution, resistance to transfer the hydrated electron, coefficient of diffusion impedance of concrete in salt water are smaller than those in fresh water; the electric double layer capacitor of concrete in salt water is greater; the phase angle index is substantially constant. That indicates the chloride ions diffused into the concrete in salt water and increase the free ion concentration in pore solution and C-S-H gel, then the resistance of pore solution electrolyte and the diffusion resistance of free charge reduced; constant of phase angle index shows chloride ions had no obvious influence on the pore structure of concrete.