Recycling Molybdenum Tailings to Produce Eco-Friendly 3D-Printed Concrete (2026-04)¶

This study develops an eco-friendly 3D printing concrete (3DPC) system fabricated entirely from industrial by-products and elucidates the mechanism by which molybdenum tailings (MT) replacement for quartz sand (SS) regulates system performance. The formulation builds upon a fluorogypsum-based binder previously optimized by our research team. A single-variable approach, varying the MT replacement ratio from 0% to 100%, was employed to systematically evaluate its impact on fresh rheological behavior, printability, and hardened mechanical properties. Results indicate that, compared to SS, the irregular geometry and high water absorption of MT significantly enhance the yield stress and thixotropy of the paste, thereby remarkably reducing the structural deformation during printing. Despite a slight reduction in early-age strength, MT incorporation significantly bolsters long-term mechanical performance. Microscopic analysis reveals a dual-effect mechanism of MT: initially, its high water absorption reduces the effective water-to-binder ratio, lowering internal humidity and retarding early hydration; subsequently, the released adsorbed water exerts an “internal curing” effect. This phenomenon, combined with the surface nucleation activity of MT, substantially promotes long-term mechanical performance. By 60 days, the interfacial transition zone (ITZ) is significantly refined, as evidenced by reduced thickness and lower overall porosity. Replacing SS entirely with MT reduces the material cost per cubic meter by 29.8%. This study achieves a sustainable design for both binders and aggregates while revealing the reinforcement mechanism of MT in solid waste matrices, providing a theoretical foundation for the high-value utilization of molybdenum tailings.