In this study, the impact of water-to-cement (w/c) ratios of belite calcium sulfoaluminate cement (BCSA) on the hydration kinetics and the electrochemical impedance spectroscopy (EIS) parameters is studied. According to the analysis of classic hydration measurements, such as calorimetry tests, chemical shrinkage content, and chemically bound water content, it can be concluded that a higher w/c ratio clearly accelerates the hydration of BCSA cement paste. The electrical resistivity of BCSA0.35 cement paste is more than 4.5 times that of BCSA0.45 and BCSA0.5, due to the gradually densified micropore structure blocking the electrical signal transmission rather than the free charged-ion content. The porosity of BCSA0.5 is 27.5% higher than that of BCSA0.35 and 7.8% higher than that of BCSA0.45, which proves the resistivity is clearly related to the variation in microstructure, especially for the porosity and pore size distribution. The novelty of this study is the linear regression with logarithm terms of electrical resistivity and classic hydration parameters such as chemical shrinkage, cumulative hydration heat, and chemically bound water is established to extend the classical expression of cement hydration degree. It indicates that the electrochemical impedance spectroscopy can be taken as a nondestructive testing measurement to real-time monitor the cement hydration process of cement-based materials.
Keywords: EIS measurement; belite calcium sulfoaluminate cement; cement hydration; resistivity.