A laboratory study of the use of lime stabilisation on contaminated and uncontaminated clays

This study presents the results of experimental research carried out to investigate the effects of lime treatment on naturally deposited kaolinite clay, containing quartz, and a contaminated clay, containing calcium sulfide and heavy metals, known as galligu. The efficacy of lime stabilisation may be evaluated using unconfined compressive strength (U CS) tests which were carried out for different lime contents (0%, 5% and 10% of the sample mass) and various curing times (7, 28 and 90 days). Chemical and mineralogical changes of the two clays were established using X - R ay diffraction (XRD) and X - Ray flu orescence (XRF) in order to establish their effect on the geotechnical properties of the stabilised materials. Lime stabilised clay demonstrated improved geotechnical characteristics including a drop in moisture content (the ratio of the mass of water to the mass of solids in soil), increase in bulk density (the weight of the soil in a given volume, in this case 1m 3 ) and decrease in air voids (pockets of air between aggregate particles in the soil). However the net geotechnical improvements in the natural clay were demonstrably less than the galligu, principally in terms of strength. Galligu as recovered has a high moisture content and the alkaline conditions were able to supply sufficient moisture and the optimum chemical environment for effective cation exchanges and pozzolanic reactions. For the natural clay the lime addition caused an increase in the optimum moisture needed for effective compaction, which was higher than the natural moisture content of the clay