Expansive clay presents a significant challenge in road construction, swelling when wet and cracking when dry. This results in pavement failure, costly repairs, and safety hazards. A recent study published in the Journal of Rock Mechanics and Geotechnical Engineering by Mohammad Saberian, Jiasheng Zhu, Rajeev Roychand, Xi Sun, Jie Li, and Chun-Qing Li investigates whether fine-grained wood biocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More (FGB) can improve the geotechnical properties of clay used in pavement subgrades. The researchers found that adding 2% biochar increased soil strength and stability, making it a promising alternative to traditional chemical stabilizers.

The team conducted a series of tests on clay samples mixed with varying amounts of biochar to assess its effects on strength, shrinkage, and swelling. The improvements stem from biochar’s porous structure and chemical composition. Biochar increases soil cohesion by filling voids, enhancing interparticle friction, and reducing the movement of clay particles. Additionally, its hydrophilic and hydrophobic functional groups interact with water, stabilizing soil moisture content. Unlike traditional stabilizers like cement or lime, which produce significant carbon emissions, biochar is a low-carbon alternative derived from organic waste, supporting sustainability goals in construction.

One key finding was that adding more than 2% biochar did not necessarily enhance soil properties further. Excess biochar reduced soil cohesion, making it less effective. This highlights the importance of optimizing biochar content for specific soil conditions.

The study demonstrates that biochar can serve as an effective and environmentally friendly soil stabilizer, offering an alternative to conventional methods. By integrating biochar into pavement subgrade construction, engineers can enhance road durability while reducing carbon footprints. Future research should explore different biochar sources and long-term field performance to refine this sustainable approach.

Source :Saberian, M., Zhu, J., Roychand, R., Sun, X., Li, J., & Li, C.-Q. (2025). Effect of fine-grained wood biochar on the geotechnical and microstructural behavior of expansive clay as pavement subgrade. Journal of Rock Mechanics and Geotechnical Engineering.