Electrochemical impedance spectroscopy (EIS) is effective tool to investigate degradation of concrete and corrosion of reinforcing steel bar. The impedance spectrum of concrete reinforced by steel bar shows many capacitive loops on the Nyquist plane. McCarter et al. [1] reported that capacitive loop in the high frequency range originated form the dielectric property of concrete absorbing water. According to the paper by McCarter et al. [1], the EIS allows the information concerning the amount of water and pore structure in concrete. We measured impedance spectra of concrete sandwiched between two stainless steel electrodes, and found that the capacitance is very large when the concrete absorbed much water. We observed the variation of capacitance during the drying process of concrete, and proposed a complicated pore structure in concrete.

Reference:

[1] W. J. McCarter and S. Garvin, J. Phys. D: Appl. Phys., 22 (1989) 1773-1776.