Electrical resistivity of compacted clay minerals

The objective of this study was to determine the electrical resistivity responses of clay minerals (sodium bentonite, calcium bentonite, illite and kaolinite) at three degrees of saturation (S _r) – that is, 40, 60 and 80% – and their correlations with pore water properties, activity, cation exchange capacity (C _EC) and porosity. Grain size distribution, Atterberg limits, C _EC, energy-dispersive spectroscopy and scanning electron microscopy (SEM) were employed for the characterisation of the minerals and identification of the possible relationship of clay properties with electrical resistivity. It was observed that oxygen, aluminium, silicon and sodium ions (by weight percentages) are major constituent elements of sodium bentonite, illite and kaolinite. The SEM images of sodium and calcium bentonites both showed flaky structures. Needle-like shapes and hexagonal crystals were demonstrated in the SEM image of illite, and six-sided hexagonal plates were observed in the SEM image of the kaolinite specimen. Electrical resistivity tests were conducted on the clay minerals at moisture contents and dry unit weights ranging from 10 to 40% and 11·8 to 14·9 kN/m³, respectively.