Geotechnical and chemical characterization of expansive clayey soil amended by biochar derived from invasive weed species Prosopis juliflora

Biochar is biomass-derived carbonaceous solid product obtained when plant-based biomass is heated in a closed environment in presence of little or no oxygen. In the present study, the biochar is produced by slow pyrolysis of Prosopis Juliflora. The use of P. Juliflora helps to reduce the threat to biodiversity as well as decrease the transmission rate of malaria, thus contributing to a sustainable environment. The biochar is uniformly mixed with expansive black cotton soil at three different percentages (5, 10% w/w) at same compaction state. Microstructural (X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscope, energy-dispersive x-ray spectroscopy), physicochemical (cation exchange capacity, pH, specific gravity) as well as geotechnical characterizations (consistency limits, free swell, permeability, California bearing ratio (CBR), shear strength) are carried out on soil with and without biochar amendment at different percentage mix by laboratory testing. It is observed that addition of biochar increases the shear strength and CBR and decreases the free swell index of the expansive soil. Overall, the study revealed that biochar-amended soils can possess excellent geotechnical properties to serve as a stabilizing material for expansive soils.