A review of bio-based stabilization methods for expansive soils

Expansive soils are notorious for their cyclic swell–shrink behaviour, often posing serious challenges to geotechnical infrastructure and leading to structural damage and high maintenance costs. Although, the traditional stabilizers such as cement and lime are effective but they are associated with significant carbon emissions and limited sustainability. In contrast, bio-based stabilization methods offer an environmentally friendly alternative and delivering comparable performance in enhancing the engineering properties of expansive soils. Bio-stabilizers such as microbial-induced carbonate precipitation (MICP), enzyme-induced carbonate precipitation (EICP) and biopolymer-based soil treatment (BPST) are utilized to enhance the soil strength, reduce swelling potential, lower permeability, and minimize environmental risks. An extensive literature studies demonstrates that the both MICP and EICP significantly improve the engineering characteristics of expansive soils, particularly by increasing strength, reducing hydraulic conductivity, and minimizing swelling and compressibility. BPST demonstrates potential for rapid early-age strength development, while MICP and EICP are more effective for strength improvement over extended duration through mineral precipitation. These biological mechanisms, when acting alone or together, rely on biomineralization and gel-matrix formation to improve bonding between particles and prevent volume changes related to moisture. A SWOT analysis suggests that bio-based has high potential for field applications; however, weaknesses remain in consistent performance and resources to develop design recommendations.