<p>To improve the strength and deformation resistance of cement-stabilized soils under dynamic loading, industrial by-product silica fume (SF) was introduced as a supplementary binder. The tested geomaterial is a particulate clay, therefore, the procedure evaluated herein pertains to cement-stabilized particulate clay, and references to “soil improvement” in this work should be understood within this specific material context. A series of dynamic triaxial tests were performed on specimens with varying SF contents (0%, 1%, 2%, 3%, and 4%) to investigate the evolution of cumulative plastic strain and dynamic elastic modulus under cyclic loading. Complementary microstructural analyses, including scanning electron microscopy (SEM), nuclear magnetic resonance (NMR), and X-ray diffraction (XRD), were conducted to elucidate the mechanisms of SF in cement hydration and soil densification. The results demonstrate that an appropriate SF content significantly enhances shear strength and deformation resistance. At 3% SF, cumulative plastic strain decreased by more than 46%, while the dynamic elastic modulus increased by nearly 50%, indicating the most favorable dynamic response. SF promotes secondary hydration and pozzolanic reactions, producing abundant C-S-H gels that fill pores and form a dense particle-gel network, thereby improving structural uniformity and stability. XRD analysis further confirmed a reduced amount of Ca(OH)₂ and an enhanced C-S-H formation, while excessive SF led to particle agglomeration and structural defects. Overall, SF is an effective, eco-friendly additive that improves the mechanical performance and durability of cement-stabilized soils, with promising engineering applications.</p>