Evaluating the impact of mine tailings wastes on the development of sustainable Ultra High Performance Fiber Reinforced concrete

The increasing demand for sustainable construction materials has led to exploring alternative resources, such as mine tailings in ultra-high-performance fiber-reinforced concrete (UHPFRC). Conventional concrete production is associated with significant environmental impact and resource depletion, necessitating the search for sustainable alternatives. This study investigates the effects of incorporating mine tailings powder (MTP) and mine tailings sand (MTS) as substitutions for cement and quartz sand on the mechanical and durability properties of UHPFRC. The current study focuses on evaluating the workability, compressive strength, indirect tensile strength, modulus of rupture, sulfate resistance, autogenous shrinkage, thermal performance, porosity, hydration kinetics, and phase composition of UHPFRC with varying MTP and MTS contents. Results indicate that the optimal mix of 15% MTP and 60% MTS enhances compressive strength by 12.49% (165.2 MPa at 90 days), reduces autogenous shrinkage by 49.28% (1023 microns at 180 days), and significantly improves sulfate resistance, with a residual compressive strength of 115.2 MPa and a mass loss of 25.4%. The workability tests show a decrease in flow spread from 274 mm in the control mix to 221 mm in the mix with 25% MTP and 100% MTS. Indirect tensile strength increased by 23.53% (23.1 MPa at 90 days), and the modulus of rupture improved by 23.04% (23.5 MPa at 90 days) with the optimal mix. Mercury intrusion Porosimetry reveals increased total pore volume, especially in larger pore sizes, with the highest intrusion observed in the mix containing 5% MTP and 20% MTS. The heat of hydration analysis shows a delayed T_max from 30 h in the control mix to 36 h with 15% MTP and 60% MTS, indicating a slower and more controlled hydration process. X-ray diffraction analysis demonstrates a reduction in peak intensities, marking a transition from crystalline to more amorphous structures with increasing mine tailings content. The improved microstructural characteristics, such as reduced porosity and enhanced hydration stability, contribute to the material's long-term durability and mechanical performance, making it a viable option for sustainable construction practices.