Mechanical properties and microstructure of highly expansive clay treated with Waste Glass Powder (WGP) and Waste Tire Textile Fiber (WTTF)

This study investigates the synergistic use of Waste Glass Powder (WGP) and Waste Tire Textile Fiber (WTTF) to enhance the strength, stiffness, and swelling properties of expansive clayey soils for pavement subgrades. While these industrial by-products show promise as stabilizers, their combined effects remain understudied. The research evaluates the impact of various proportions of WGP (0–15 %) and WTTF (0–2 %) after 7, 28, and 56 days of curing to enhance subgrade performance. The methods employed include a series of laboratory experiments, such as Unconfined Compressive Strength (UCS) and Indirect Tensile Strength (ITS) tests, to evaluate the direct strength properties of the treated soils. Ultrasonic Pulse Velocity (UPV) tests are used to characterize the stiffness development, and swelling tests assess the ability of the additives to mitigate expansive behavior. Additionally, Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), and Energy-Dispersive X-ray Spectroscopy (EDS) analyses provide a detailed micromechanical interpretation of the observed performance trends. The results indicate that the optimal combination of 10 % WGP and 1 % WTTF yields the best overall performance, with UCS values increasing more than fivefold and reaching a maximum of approximately 1700 kPa. This represents a significant improvement compared to untreated soil, suggesting the potential of these additives to substantially enhance soil stabilization. This research also highlights the remarkable improvement in the ITS of the treated soil, which exceeds the minimum requirement for the application of cementitious stabilized materials in flexible pavement construction. Furthermore, the swelling potential of the treated soil is effectively controlled, especially under typical surcharge conditions encountered in subgrade applications. The findings demonstrate the synergistic effect of WTTF reinforcement in WGP-stabilized soils, improving both strength and ductility, making it a promising approach for developing sustainable materials for flexible pavement construction. This research contributes novel insights into the use of industrial waste materials for soil stabilization, highlighting their effectiveness and environmental benefits.