Effect of partial replacement of bentonite with biochar in liner soils

Biochar made from pyrolysis of biomass has wide applications as a soil amendment to reduce emission of greenhouse gases and improve the geotechnical properties of soil. Bentonite enhanced sand mixes are widely used as liner material in construction practice of landfills. Experimental investigation on partial replacement of bentonite with biochar was carried out in compacted M sand bentonite mix (80% M sand and 20% bentonite) which satisfied the requirements of liner soils. Biochar prepared from wood shavings using in-house developed pyrolysis kiln and rice husk biochar prepared using heap method were used in this study. The effect of partial replacement of 10% and 15% bentonite with both wood and rice husk biochar was studied. Examination of the results showed that in both wood and rice husk biochar samples, increase of biochar content decreased the maximum dry unit weight and increased the optimum moisture content. The samples with 10% biochar gave hydraulic conductivity less than 1×10−9 m/sec. In both wood and rice husk biochar samples, free swell, strength, and cracking potential decreased with increase in biochar content. Results indicate that both wood and rice husk biochar up to 10% can effectively replace bentonite in compacted M sand bentonite mixtures.