Electrochemical impedance spectroscopy monitoring of hydration behaviors of cement with Na₂CO₃ accelerator

Non-destructive testing methods such as electrochemical impedance spectroscopy are promising in assessing the long-term properties of cement-based materials. However, the inherent correlation between electrical properties and cement hydration parameters is still unclear, which hinders the application of this method in the replacement of the traditional hydration test method. The hydration of cement with Na₂CO₃ was investigated using electrochemical impedance spectroscopy combined with the conventional characterization methods. It is found that Na₂CO₃ facilitates the early-age hydration but retards the later stage hydration with the same trend in the development of compressive strength. The mechanism of Na₂CO₃ on cement hydration is revealed through microstructure characterization results which are related to the diminishing of AFt and excess formation of CH. The resistivity evolution of cement pastes well-captured the hydration process altered by Na₂CO₃. And the correlation between microstructure, the hydration products and the electrical resistivity of cement paste is proposed to follow the linear or exponential functions. All these results indicate that electrochemical impedance spectroscopy is a promising method for characterizing both the microstructure and macroscopic properties of cement-based materials.