Electrical Conductivity, Dielectric Permittivity, and Degree of Saturation of Cement Mortar at Low Radio Frequencies

Abstract

Abstract The relationship between the electrical properties and the degree of moisture saturation (DoS) in cement-based materials is a topic of interest with regard to material durability. In this article, an impedance-based approach is presented to characterize the electrical properties as a function of DoS using simplified instrumentation and a new measurement technique. The variation of the real and imaginary parts of the impedance is investigated for saturated and partially saturated conditions at electromagnetic radio frequencies (RF) between 100–500 kHz. Mortar prism samples with water to cement ratios (w/c) of 0.60 and 0.70 are used. A circuit model is proposed to explain the behavior and to calculate the bulk conductivity and permittivity for various saturation degrees. The bulk conductivity of the material is found to follow a systematic pattern for various DoS and at different excitation frequencies, which facilitates the establishment of an empirical quantitative relationship between conductivity and the DoS. Moreover, the enhancement of bulk permittivity at low RF is noticed, and its variation for various DoS is investigated.