Mechanism of Enzyme Stabilization for Expansive Soils Using Mechanical and Microstructural Investigation

Expansive soils are susceptible to ground movements and are problematic to overlying geotechnical structures. There is a growing shift to use nontraditional sustainable and economical alternatives. To date, limited research is available on investigating the reaction mechanism of nontraditional soil stabilization; thus, this research aims to fill this gap in the knowledge. A series of experiments was conducted to assess the mechanical and hydraulic behavior of field expansive soil with the enzyme-based soil stabilizer. Moreover, the reaction mechanism of enzyme soil stabilization was studied using microstructural-driven analytical techniques. The results indicate substantial increase in California bearing ratio, unconfined compressive strength, and resilient modulus with a considerable reduction in permeability with the addition of enzymes into the expansive soil. The enzyme additive is adsorbed by the clay particles, which reflects a reduced affinity for water, an improved density, and a reduced ingress of water within the soil. Adding enzymes causes the expansive clay mineral lattices to relax, as the enzyme stabilizers penetrate the inner layers leading to expansion and subsequent moisture entrapment of the inner layers, emphasizing densification and a reduced affinity for water. The outcomes from the study are beneficial for the understanding of enzyme-based ground improvement to inhibit the expansive nature of reactive soils.