Investigating drying behavior of cement mortar through electrochemical impedance spectroscopy analysis

In this research, electrochemical impedance measurements were taken on cement mortar with different levels of drying. The impedance spectrum was analyzed with equivalent circuit model, through which the drying behavior was investigated. A model considering resistivity distribution along the drying direction was proposed. For drying of mortar, two different schemes (direct drying and ethanol-pretreated drying) were adopted. Moreover, the influence of hydration time of mortar on drying was also evaluated. Test results showed that the proposed model fitted well with both symmetric and asymmetric spectra for different levels of drying. For cement mortar directly dried at 50 °C for different durations (1, 4, 24, and 48 h), the peak resistivity and drying depth increased with drying time. The ethanol-pretreated mortar showed similar behavior. Moreover, the hydration time of cement mortar was another important factor to influence the drying depth. The proposed model for electrochemical impedance spectrum interpretation provides a low-cost and effective non-destructive approach for understanding the drying behavior of cementitious system.