Effect of leachate on the mechanical and microstructural characteristics of the compacted clay liner stabilized with water treatment sludge (WTS), waste travertine, and sodium lignosulfonate (NLS)

• Stabilized clay liners were evaluated under leachate exposure. • Optimum mix (10% WTS + 10% travertine + 1% NLS) enhanced V s by 226%. • Leachate-submerged samples exhibited 31% lower UCS compared to dry conditions. • Waste-based stabilization enhanced durability for landfill liner applications. • Stabilized CCLs showed 26% higher UCS versus untreated soil under dry conditions. This study aimed to investigate the effects of leachate exposure on stabilized compacted clay liners, determine the optimal mixture of water treatment sludge (WTS), waste travertine, and sodium lignosulfonate (NLS) for enhanced liner performance, and characterize the microstructural changes induced by leachate interaction. To this end, soil samples were stabilized with varying proportions of WTS (0-15%), waste travertine (0-15%), and NLS (0-1.5%). The mixtures were then compacted at optimum moisture content and subjected to three curing conditions of 7, 28, and 90 days. A series of laboratory experiments, including unconfined compressive strength (UCS), bender element and microstructural analyses, were conducted to evaluate the properties of the stabilized clay liner before and after exposure to leachate. The results indicate that the incorporation of 10% WTS, 10% travertine, and 1% NLS showed the best overall performance, providing the highest strength, shear wave velocity (V s ) and the most compact microstructure. The exposure to leachate (collected from a local municipal solid waste) generally resulted in a decrease in the UCS values across all the tested mixtures; the most notable reduction in strength was observed in the samples that were mixed with water and then submerged in leachate (i.e., W-LC). The optimum mixture achieved UCS values of 1202 kPa (W-D) and 826 kPa (W-LC) after 90 days, representing the best and worst-case conditions. Stabilizers enhanced rigidity and compaction, increasing shear wave velocity (Vₛ) to 358 m/s. The optimal blend exhibited strong leachate resistance, demonstrating its suitability for durable landfill liners.