Abstract: To address the low strength issue of mica schist, we propose a new type of powder curing agent (CLFD) consisting of cement, lime, fly ash, and desulfurized gypsum to enhance subgrade soil in association with tailings slag (TS). Mechanical and durability properties of solidified soil with varying amount of curing agent and curing age were investigated through indoor mechanical tests. By adopting X-ray diffraction analysis and scanning electron microscope test, the mechanism of strength formation in solidified soil was revealed. Results suggest that soil samples solidified with CLFD-TS exhibit significant improvements in mechanical properties, water stability, and dry-wet cycle resistance. A mixing ratio of curing agent no less than 6% when immersed in water for 9 days meets specification requirements in terms of bearing ratio and modulus of resilience. Microscopic analysis shows the presence of C-S-H, C-A-H gel, AFt, and CaSO₄ crystals in the solidified soil, which enhance soil properties by cementing and filling soil particles. Early strength of CLFD-TS-solidified soil comes from the physical skeleton gradation improvement provided by tailings slag and the hydration effect of cement components. Late strength is provided by the pozzolanic effect of the curing agent. Finally, a micro mechanism model of CLFD-TS-solidified soil is proposed to provide a theoretical basis for similar studies.

Key words: road engineering, mica schist strongly weathered soil, CLFD curing agent, mechanical property, curing mechanism