Enhancement of micro-mechanical characteristics of expansive soil through synergistic incorporation of jute and nylon fibers with cement

• Synergistic use of natural and synthetic fibers with cement boosted soil performance. • Optimal 0.5 % fiber mix improved strength while minimizing shrink-swell behavior. • Stabilization met subgrade s, optimizing materials and enhancing durability. • SEM and FTIR confirmed denser soil matrix and enhanced bonding. • Study demonstrates a sustainable fiber-cement approach for stabilizing expansive soils. Expansive soils, with their pronounced swell-shrink behavior, pose significant challenges to structural stability and durability. This study introduces an innovative stabilization approach by integrating natural (jute) and synthetic (nylon) fibers with cement to enhance the mechanical properties and volumetric stability of expansive soils. The unique synergy between natural and synthetic fibers is a key feature, leveraging the surface roughness and bonding capacity of jute with the durability and tensile strength of nylon to create a robust and stable soil-fiber-cement matrix. Experimental evaluations, including unconfined compressive strength (UCS), indirect tensile strength (ITS), California bearing ratio (CBR), 1D swell tests, and linear shrinkage tests, revealed significant improvements: UCS, ITS, and CBR values increased by up to 1380 %, 1565 %, and 1450 %, respectively. The inclusion of fibers, in combination with cement, significantly enhanced UCS, ITS, and CBR values by up to 109 %, 200 %, and 11 %, respectively, compared to cement-only stabilization. The optimal fiber content of 0.5 % for both jute and nylon maximized these enhancements, effectively mitigating moisture-induced volume changes by reducing free swell strain and swell pressure by over 90 %. Linear shrinkage was also substantially minimized, improving soil durability and structural integrity. Microstructural and chemical analyses using scanning electron microscopy (SEM) and Fourier-transform infrared (FTIR) spectroscopy confirmed the formation of a dense matrix with enhanced particle interlocking and the development of calcium silicate hydrate (C-S-H) gel, providing chemical stabilization. The findings underscore the potential for this methodology to revolutionize soil stabilization practices, offering durable and environmentally responsible options for geotechnical and civil engineering applications.