Enhancing the geo-mechanical behaviour of lime-treated bentonite with silica fume

The current paper explores the geo-mechanical performance of the potential inclusion of silica fume (SF) in lime-treated bentonite as liners for landfills, as a novel approach to improve the engineering properties of bentonite and its application in landfill containment systems. Thus, the combined effects of silica fume and lime on the key engineering characteristics (i.e., strength, swelling and permeability) of bentonite specimens were investigated. Various SF proportions (0–7%) were mixed with 7% lime to identify the optimum content of SF. Specimens of 5% SF were treated with 7% of lime and cured at 20 °C for varying periods up to 9 months. The evaluation also involved incorporating 7%, 9% and 11% of lime into bentonite and cured at 20 °C and 40 °C. Moreover, oedometer tests were conducted on specimens having varying proportions of SF (0–6%) with 7% lime, with immediate testing after compaction. Furthermore, microstructural analysis was conducted using the scanning electron microscope and energy-dispersive X-ray spectrometers techniques. The findings revealed a significant enhancement in the compressive strength of treated bentonite when a combination of 7% lime and 5% SF was added and cured for 28 days at both 20 °C and 40 °C, with increases of 390% and 664%, respectively. Incorporating 5% SF into lime-treated bentonite resulted in 79% reduction in swelling pressure, compared to untreated ones, and 15% decrease compared to lime-treated bentonite without SF, in addition to a decrease in permeability to 4.75 × 10^–10. The findings exhibited favourable effects on improving the geotechnical properties by incorporating lime and 5% SF.