Mechanical properties of graphite tailings ultra-high-performance concrete for prefabricated building joints in cold regions

This research investigates mechanical properties of graphite tailings ultra-high-performance concrete (GT-UHPC) for prefabricated building joints in cold regions, aiming to address technical bottlenecks of high cost and harsh curing conditions in conventional UHPC applications. By partially replacing river sand with size-classified graphite tailings, this research systematically explores effects of replacement rates on basic physical properties, static/dynamic mechanical performance, thermal stability, hydration products and microstructure of GT-UHPC. GT-UHPC-30 (30 % content) exhibits optimal performance, 28-day compressive strength is 139.20 MPa, flexural strength is 24.74 MPa and elastic modulus is 39.18 GPa, with significantly enhanced impact resistance under high-pressure loading (162.75 MPa at 6 bar). Microstructurally, moderate graphite tailings promote hydration reactions, optimize pore distribution with reducing macropores and increasing gel pores, and strengthen interfacial transition zone. Economically, GT-UHPC-30 reduces material costs by 20.23 % and carbon emissions by 16.98 %. This research provides theoretical support for design and engineering application of high-performance prefabricated joint materials in cold regions.