Time-Dependent Properties and Model Analysis of Rheology for Fresh Sulphoaluminate Cement Paste Evaluated by Electrochemical Impedance Spectroscopy

In this paper, the time-dependent properties of rheological parameters (${\tau }_0$, $\eta$, $A$) and electrochemical parameters ($R_b$) are investigated by preparing sulphoaluminate cement pastes with different water-to-cement ratios ($\mathrm{W}/\mathrm{C}$) of 0.3, 0.4, and 0.5, respectively. A new rheological microstructure model is proposed by combining hydration kinetics with a newly introduced hydration stage, with electrochemical parameter $R_b$. Meanwhile, the time-dependent nature of rheological parameters was evaluated by electrochemical parameters. The experimental results show that the time-dependent properties and microstructural evolution are closely related to the water content of cement paste. Based on hydration kinetics, the reconstruction curve of hydration rate conforms to the Krstulović–Dabić model and the hydration mechanism belongs to NG-I-D (where NG, I, and D stand for nucleation and crystal growth, interactions at phase boundaries, and diffusion, respectively). The time-dependent property of electrochemical parameter $R_b$ can be divided into four stages, which conform to the mathematical model of $R_b=kt$. However, the hydration mechanism that dominates those four stages is different. In addition, the rheological parameters (${\tau }_0$, $\eta$, and $A$) have a good linearly time-dependent relationship with electrochemical parameter $R_b$. As an in-situ nondestructive method, the electrochemical analyzer is feasible to monitor and evaluate the time-dependent properties of cement rheology.