This study investigates the development of eco-friendly Ultra-high Performance Concrete (UHPC) through the substitution of river sand with molybdenum tailings. A comprehensive microstructural characterization was initially conducted to evaluate the distinctive aggregate properties between molybdenum tailings and river sand. Systematic experimental analyses were performed to assess the variations in mechanical properties, workability, durability, environmental performance, and economic viability of UHPC incorporating molybdenum tailings at varying mass replacement levels (0 %, 25 %, 50 %, 75 %, and 100 %). The experimental results reveal that while molybdenum tailings exhibit similar adsorption characteristics and pore structure distribution to river sand, they demonstrate distinct angular morphology, enhanced specific surface area, and elevated surface roughness. At 100 % replacement, despite affecting workability, the chloride ion resistance improved by 25.6 %, while maintaining the molybdenum ion leaching rate below 0.07 mg/L, ensuring safety for buildings and human health. Although negatively impacting hydration product formation, microstructural morphology, and porosity, the 28-day compressive strength reached 109.32 MPa with a flexural strength of 12.7 MPa, showing slight improvement compared to river sand UHPC. Economic analysis showed a 13 % reduction in production costs, while life cycle assessment indicated improved environmental performance across all indicators. This investigation validates the application potential and economic value of utilizing molybdenum tailings as a river sand substitute in environmentally sustainable UHPC production, providing experimental evidence for future research initiatives in this domain.
