Synthesis and mechanisms of synergistic quartz clustering in alkali-activated solid waste-based grouting materials for heavy metal immobilization

To address bottlenecks such as poor underwater performance and unclear heavy metal migration mechanisms in solid-waste-based grouting materials, this study developed a novel cement-free, all-solid-waste grouting system using coal gangue, fly ash, and silica fume. The research focused on investigating its underwater adaptability and heavy metal solidification mechanisms. Through multi-factor proportion optimization, the engineering performance of the slurry was systematically evaluated, and its underwater diffusion behavior was elucidated via numerical simulations. Microscopic characterization and theoretical calculations further revealed the structural evolution of heavy metals during solidification. The results indicated that an optimal formulation (40 wt% CG, 25 wt% FA, and 35 wt% SF with admixtures) achieves a synergistic balance between fluidity and anti-washout properties. Mechanistic studies confirmed that heavy metal stabilization is driven by a dual mechanism of "surface adsorption" and "network fixation": the quartz crystal surfaces exhibit a strong adsorption affinity for both heavy metal ions and silicon-oxygen units; simultaneously, the robust interactions among these silicon-oxygen units drive the formation of a dense aluminosilicate gel network, thereby synergistically enhancing the solidification effect. Computational results showed that the adsorption affinity of Se 4 + on the quartz (001) surface and 2Q 1 monomers is significantly higher than that of As 3+ , explaining the divergent solidification behaviors. Environmental and economic assessments demonstrate that this system offers substantial advantages in carbon mitigation and cost control, highlighting its promising potential for sustainable engineering applications.