Effects of solid waste-based cementitious material partial replacement on the mechanical properties and microstructure of total tailings concrete

For the utilization of tailings solid waste materials and green mine development, this study proposes a solution for total tailings concrete (TTC) prepared by combining solid waste cementitious auxiliary materials with total tailings aggregates and basalt fibers. The UCS, flexural resistance tests, and DIC were used to analyze their mechanical properties and failure characteristics. The XRD, Lf-NMR, and SEM were applied to analyze the hydration process and microstructure of the experiments. The results show that concrete strength initially increases, then decreases as silicon fume content rises, while fly ash and carbide slag content are negatively correlated with strength. The recommended mix ratio is OPC:SF:FA:CS = 5:10:5:10. This ratio represents a trade-off between cement reduction and mechanical performance, rather than a universally optimal composition. It achieves a UCS of 21.18 MPa and a flexural strength of 4.65 MPa, while reducing OPC usage by 83.33% and consuming 250 kg/m 3 of solid waste. The mechanical strength of TTC is mainly dominated by the C-S-H gel: an appropriate amount of silica fumes can suppress crack propagation, while excess fly ash and carbide slag can cause concrete loosening. C-S-H gel facilitates the material's transition from sudden brittle shear to tensile failure, while unreacted solid waste particles act as microdefects that trigger stress concentration and shear collapse sites. This study demonstrates profound theoretical and practical value in promoting the sustainable evolution of mine support materials.