Geotechnical Enhancement of Sand-Bentonite Liners Using Bagasse Ash: A Sustainable Approach to Landfill Barrier Systems

Abstract

This research investigates the geotechnical enhancement of bagasse ash modified sand-bentonite mixtures (SBMs) for application as sustainable landfill liner materials. With increasing concern over the environmental degradation caused by leachate migration from landfills and the limitations of conventional liner systems under heavy metal exposure, the study explores the potential of incorporating sugarcane bagasse ash, a pozzolanic agro-industrial by-product, into SBMs to enhance their geotechnical performance. Laboratory tests were conducted to assess index properties, compaction characteristics, shear strength, and bearing capacity.

Results indicated that the specific gravity of the mixtures generally decreased from 2.64 to 2.54 with increasing bagasse ash content, although minor intermediate fluctuations were observed. Atterberg limits showed a progressive increase in plasticity index, suggesting improved sealing and moisture retention. Compaction tests revealed increasing optimum moisture content (9.44–25.80%) and a decrease in maximum dry density from 1.85 to 1.51 Mg/m³, reflecting lighter but more moisture-demanding materials. Shear strength parameters demonstrated a non-linear response: initial additions of bentonite and bagasse ash reduced shear resistance, but higher proportions promoted recovery and stabilization due to pozzolanic gel formation.

The CBR values decreased from 11.95% to 1.20%, indicating a functional shift from structural support to hydraulic barrier. The optimum balance between shear resistance, deformability, and low bearing capacity suitable for landfill barriers was observed at a mix containing 10% bentonite and 12.5% bagasse ash. The findings highlight bagasse ash as a viable, eco-friendly additive that improves contaminant retention, reduces permeability, and enhances the integrity of engineered barrier systems.