Early assessment of hydration and microstructure evolution of belite-calcium sulfoaluminate cement pastes by electrical impedance spectroscopy

In this paper, the interconnectedness among the electrical resistivity, the calorimetric heat and the chemical shrinkage of high Belite calcium sulfoaluminate (BCSA) cement are discussed. Microstructure analyses by using XRD, NMR, ICP-MS and SEM are applied to further demonstrate the relationship among the microstructure, the compositional variation and the electrical resistivity of the hydrated cement paste. Two distinctive hydration stages can be differentiated from the BCSA cementitious materials. First stage is mainly controlled by hydration process of both the ye'elimite and the gypsum, and the second stage is mostly controlled by the formation of AFm and amorphous phases as a secondary hydration process. According to the classic equation depicted the hydration degree of cementitious materials, a specific mathematical equation combining not only traditional parameters but also the electrical resistivity is proposed for the BCSA.