Addressing aeolian sand's (AS) subgrade inadequacies (poor gradation, low cohesion) and overcoming traditional cement's high carbon emissions and alkali activation's reliance on external strong alkalis, this study introduces a full solid-waste cementitious material (FSWCM) binder. It combines carbide slag, ground-granulated blast furnace slag, fly ash, silica fume, and desulfurization gypsum at a 4:3:2:3:2 mass ratio. The effects of FSWCM dosage (0-40%) and compaction degree (94-100%) on AS's compaction behavior and mechanical properties were investigated, with the solidification mechanism and environmental safety characterized via XRD, FTIR, SEM-EDS, TG-DTG, and ICP-OES. Results reveal that maximum dry density rises before declining with FSWCM content. Higher binder dosage and compaction significantly improve shear strength, resilient modulus, CBR, and UCS. At 40% dosage and 100% compaction, the 28-day UCS reaches 6.88 MPa, with resilient modulus and CBR increasing by 1.98 and 1.53 times, respectively; amended specimens exhibit improved water stability, higher stiffness, and a plastic-to-brittle failure transition. Microstructural analyses reveal that the improvement arises from a combined mechanism of physical gradation and chemical bonding. At low dosages, solid-waste particles densify the material. At higher dosages or longer curing durations, carbide slag and slag induce an alkaline environment that activates reactive SiO2 and Al2O3 in fly ash and silica fume, facilitating the formation of C-(A)- S-H gels, Aft, and calcium carbonate as well as a dense binding network. Heavy metal testing confirm no environmental hazards. FSWCM offers a sustainable solution to improve AS subgrades in desert and semi-arid regions, facilitating low-carbon infrastructure.