Effect of state of compaction on the electrical resistivity of sand-bentonite lining materials

Abstract

Sand-bentonite mixtures are often used as lining materials in various containment systems. Leachate leakage can affect the electrical resistivity of sand-bentonite liners, and consequently, resistivity measurements can be used as an effective tool to detect contamination. This paper presents the results of an investigation into the effect of the state of compaction on the resistivity of sand-bentonite mixtures, with the bentonite content varying from 0 to 100%. The resistivity of mixtures at their different states of compaction are investigated. The resistivity of the lining mixture decreases as the water content increases, but the rate of decrease is reduced significantly above a specific water content for each mixture. Furthermore, this specific water content was noted to be on the wet-side of the optimum for sand-bentonite mixtures and on the dry-side of the optimum for pure sand and pure bentonite. Increasing bentonite over 20% demonstrates insignificant impact on resistivity. It is observed that at higher water contents, bentonite addition has negligible effect on resistivity. Correlations applicable to the sand, bentonite and pore fluid used in this study have also been presented. The results from this study may be useful for soil contamination detection, liner leak detection, development of sensors, soil and corrosion studies, etc. in Australia as well as worldwide for similar sands.