Composite Dielectric Model for Cement Concrete Considering Water Saturation

Water has a significant impact on the dielectric constant of materials. As a multiphase composite material, the effect of water content must be taken into account when modeling the composite dielectric of cement concrete. Cement concrete traditionally has been thought of as a three-phase mixed material consisting of mortar, aggregate (limestone), and pores (air). Water was used as a constituent material of cement concrete in this paper, and its content was described in terms of water saturation. By abstracting the components of cement concrete into independent medium units and arranging them according to certain rules, the four-phase mixing model of cement concrete can be established. To investigate the effect of water, the dielectric constant of cement concrete was measured using a network analyzer at various water saturation levels. The experimental results show that water significantly can enhance the dielectric constant of cement concrete, and this effect is related to porosity: the higher the water saturation, the faster the dielectric constant increases. According to the established concrete four-phase mixed model, combined with the parallel plate capacitor theory, a composite dielectric model considering water saturation was developed which can improve the prediction accuracy under different water saturation conditions and provide a foundation for the application of ground-penetrating radar (GPR) in the quality inspection of cement concrete pavement.