Impact of pore water conductivity and porosity on the electrical conductivity of kaolinite

The purpose of this study is to quantify the magnitudes of surface conduction and pore water conduction from the measured electrical conductivity of kaolinite, with the ultimate goal of estimating the electrical conductivity of kaolinite with a wide range of pore water conductivities (σ_w = 0.013–3.356 S/m) and porosities (n = 0.368–1.0). Therefore, the theoretical background of the electrical conductivity in soils was reviewed, and electrical conductivity measurements on kaolinite were performed using both slurry and consolidation tests in this study. The results of this study demonstrate that the variations of measured electrical conductivity (σ_mix) with n are debatable according to the values of σ_w, because a decrease in n results in both an increase in surface conduction (K_s) and a decrease in pore water conduction (K_w); this causes the relative magnitude of K_s compared to that of K_w to vary with σ_w and n. Consequently, this study develops the relation between the porosity-normalized K_s/K_w and 1/σ_w. Additionally, the surface conductivity of the tested kaolinite is back-calculated and compared with the previous relationship between K_s and zeta potential of kaolinite. The measured and estimated σ_mix values are compared with the varying pore water conductivity and porosity values.