Abstract
The hydration process of cement materials with coal metakaolin (CMK) was investigated by electrochemical impedance spectroscopy (EIS) using a new equivalent circuit model in this study. The results suggested that the electrochemical impedance characteristics of blended cement materials vary significantly with the content of CMK. The impedance parameters R-s and R-ct1 associated with the changes in the cement microstructure increased with increasing hydration time and CMK content across the entire hydration process. Additionally, the fractal dimension d, which characterizes the complexity and density of the pore structure, showed a trend similar to those of the above impedance parameters, but the fractal dimension d(s), which characterizes the surface properties of the pore structure, showed the opposite trend. In addition, there was a significant correlation between the impedance parameter R-ct1 and the compressive strength of the blended cements with different CMK contents and hydration times.