Wang, et al (2024) Undrained shear strength of biochar-assisted biocemented calcareous sand by biostimulated microbially induced calcium carbonate precipitation. Journal of Rock Mechanics and Geotechnical Engineering. https://doi.org/10.1016/j.jrmge.2024.11.039

Calcareous sand, common in tropical regions, often suffers from low shear strength, posing challenges in construction. A recent study explored how biochar-assisted biostimulated microbially induced calcium carbonate precipitation (MICP) can enhance the shear strength and stability of this material.

The MICP process relies on microbial activity to induce calcium carbonate precipitation, effectively binding sand particles. Biostimulation, one approach to this process, boosts native microbial activity through nutrient additions. However, its effectiveness can be limited by environmental factors or microbial diversity. To address these limitations, the study integrated 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 into the MICP process.

Key findings include:

• Biochar’s Role: Acting as a nucleation site, biochar significantly improved calcium carbonate cementation, enhancing sand stability. Powdered biochar, due to its fine size, was more effective than flaked biochar in uniformly increasing cementation content.
• Improved Shear Strength: Biochar-assisted samples exhibited a notable transition from strain-softening to strain-hardening behavior at 7-10% strain.
• Failure Criterion Insights: The study evaluated shear strength under varying conditions, finding the A̅ = 0 failure criterion more conservative compared to others.

Additionally, biochar enhanced microbial ureolytic activity, facilitating better calcite formation. These findings suggest that biochar-assisted MICP could offer a sustainable solution for improving calcareous sand’s geotechnical properties, especially in construction and environmental remediation contexts.

Further research is recommended to optimize biochar types and application methods for broader field use.