Mechanical, microstructural, and environmental-economic performance of cement-lithium slag stabilized clay as a pavement base

Abstract The rapid growth in lithium production has led to a substantial accumulation of lithium slag, an industrial by-product. To promote the sustainable recycling of this waste and alleviate environmental concerns, this study explored the feasibility of incorporating lithium slag into cement-stabilized clay for use as a pavement base. The study comprehensively evaluated the mechanical properties, microstructural characteristics, and environmental-economic viability of cement-lithium slag stabilized clay with different lithium slag substitution rates (0, 6.25%, 12.5%, 18.75%, 25%, and 50%). Experimental findings indicated that the unconfined compressive strength (UCS) exhibited a convex trend where it initially rose and subsequently declined as the substitution rate increased, culminating in a peak value at an 18.75% substitution rate. Specifically, after 7 days of curing, the specimen with 18.75% substitution rate demonstrated a distinct strength enhancement of 37.76% over the 0 substitution rate, suggesting its suitability for higher-traffic pavement base. Regarding durability, although the UCS fluctuated (increasing then decreasing) with the number of wetting–drying cycles, the inclusion of lithium slag effectively improved the material’s resistance, with 18.75% again proving to be the optimal substitution rate. Specimen photos post-UCS testing and wetting–drying cycles revealed that cement-lithium slag stabilized clay exhibited the least severe failure characteristics at a 18.75% substitution rate. At the 18.75% substitution rate, reactive SiO₂ and Al₂O₃ in lithium slag underwent pozzolanic reactions with Ca(OH)₂ generated from cement hydration, forming additional C-S–H, networked C-A-S–H, and ettringite crystals, thereby increasing the strength of the stabilized clay. At the 18.75% substitution rate, cement-lithium slag stabilized clay achieved the best balance among compressive strength, environmental benefits, and economic efficiency. These findings offer valuable insights for utilizing cement-lithium slag stabilized clay in road base construction.