<p>This study addresses the high costs and environmental impacts associated with traditional nanoparticles and the extraction of natural resources. It proposes the innovative use of seashell waste, ground to nanoscale, as a sustainable alternative to nano-CaCO₃ for stabilizing dredged sediments in land reclamation. By repurposing approximately 20 million tons of annual seashell waste, the research offers a dual solution for waste management and soil stabilization. The research evaluates the effects of nanoscale seashell powder on the strength development, reaction kinetics, and microstructural changes of alkali-activated ground granulated blast furnace slag-stabilized dredged sediments, with comparative assessments against pure nano-CaCO₃. Results demonstrate that nanoscale seashell powder exhibits a nucleation effect similar to nano-CaCO₃, accelerating the hydration reaction of alkali-activated ground granulated blast furnace slag and enhancing strength development. A 10% nanoscale seashell powder content improves strength by 124%, 74%, and 41% after 3, 7, and 28&#xa0;days, respectively. Notably, at 28&#xa0;days, the strength enhancement achieved with nanoscale seashell powder (41.4%) is significantly higher than that with nano-CaCO₃ (18.4%). This superior performance is attributed to the organic components within the layered structure of seashells, which provide anti-agglomeration properties, resulting in a smaller effective particle size in water-based dispersions compared to nano-CaCO₃. Furthermore, the organic layers adsorbed onto nanoscale seashell particles impart hydrophobicity, reducing the liquid limit of the dredged sediments and inter-particle distances, thereby decreasing free water content and enhancing soil strength. Overall, the findings position nanoscale seashell powder as a renewable, low-carbon additive in soil stabilization, contributing to sustainable geotechnical practices and resource conservation.</p>