Mechanical properties and micromechanisms of solid waste stabilized aeolian sand improved by nano- CaCO₃ and fibers

Aiming to address the dual problems of industrial solid waste storage pollution and insufficient performance of aeolian sand subgrades in cold and arid regions, this study uses industrial solid wastes (blast furnace slag and fly ash) as an alkali-activated matrix to prepare stabilized aeolian sand. On the basis of realizing the utilization of bulk solid waste, a synergistic modification system with nano-CaCO₃ (NC) and basalt fiber (BF) is constructed. Through macroscopic mechanics and freeze-thaw cycle tests, combined with DIC technology, mesoscopic simulation and microscopic analysis, the reinforcement mechanism of composite materials was explored. The results demonstrate that Nano-CaCO₃ optimizes matrix compactness through the micro-aggregate filling effect and nucleation effect, and synergizes with the three-dimensional bridging crack-resistance effect of basalt fiber to improve material performance. After hybrid modification, the compressive strength increases by 23.8%, and the splitting tensile strength increases by 28.8%. The strength loss rate can be controlled within 65% after 20 freeze-thaw cycles. DIC analysis reveals the differential characteristics that nano-modification induces strain localization while fiber modification induces strain dispersion: the shear band width reaches 200-300 px, and the peak shear strain γ_max is controlled between 0.08 and 0.10. Microscopic observations further elucidate the synergistic mechanisms: nanoparticles induce a transition from tensile to shear debonding, while fibers dissipate energy through pull-out and bridging actions. This multi-scale synergy achieves a significant improvement in the "strength-toughness-stability" of the composite. This study provides a theoretical basis for the utilization of solid waste resources in cold and arid areas and the freeze-thaw resistance design of aeolian sand subgrade engineering.