Basalt fiber reinforcement cementation with bio-inspired carbonate precipitation for stabilization of expansive soil

This study presents a sustainable method to enhance expansive soil performance by integrating enzyme induced carbonate precipitation (EICP) with basalt fiber (BF) reinforcement. Laboratory experiments were conducted using an optimized EICP 0.75 mol/L concentration and 1.5% BF (12 mm length). The results demonstrated that the combined treatment substantially reduced the swelling pressure and permeability (k_s) by up to 95% and 72%, respectively. This combined approach surpassed the effectiveness of the individual treatments, as EICP alone resulted in an 80% decrease in swelling pressure and a 63% reduction in k_s. Additionally, synergetic treatment enhanced the engineering properties of the expansive soil. Specifically, the unconfined compressive strength increased 136%, cohesion 58%, internal friction angle 89%, unsoaked CBR 738%, and soaked CBR 911%, respectively. These enhancements were considerably more substantial than those obtained through EICP treatment alone, which yielded improvements of only 66, 43, 48, 441, and 435%, respectively. Additionally, microscopic analysis, scanning electron microscopy, demonstrated that while EICP deposits calcium carbonate within soil pores, the incorporation of BF provided additional structural reinforcement by bridging particles and enhancing interfacial bonding. These results underscore the combined effect of bio-cementation and fiber reinforcement, presenting an eco-friendly and durable technique for enhancing expansive soils in civil engineering projects.