Effect of Wood-Based Biochar on the Engineering Properties of Medium Plasticity Clay

This research investigates the impact of wood-based biochar on the engineering properties of medium plasticity clay obtained from Perryville, Maryland. The clay was amended with biochar at volumetric contents of 3%, 6%, 9%, 12%, and 15% and subjected to a comprehensive suite of index and classification, compression, and shear strength laboratory tests. Results indicate that increasing biochar content leads to higher liquid limits and plasticity indices, a decrease in dry unit weight, and a higher optimum moisture content. Compression tests revealed increased compressibility and final void ratio with higher biochar content, likely due to biochar’s porous structure. Direct shear tests showed consistent improvements in shear strength parameters, including increases in both the internal friction angle and cohesion. Unconfined compression tests also demonstrated higher strength and ductility in biochar-amended samples. These findings support the potential of wood-based biochar as a sustainable and effective soil amendment for improving the geotechnical performance of clayey soils.