Research on the preparation of eco-economical ultra-high performance concrete utilizing graphite tailings resources

Abstract

Ultra-High Performance Concrete (UHPC) employs river sand as its primary aggregate due to the absence of coarse aggregates, resulting in high production costs and significant ecological impacts, limiting its broader application. To mitigate these challenges, this research investigates the substitution of river sand with industrial waste graphite tailings (GT) in UHPC production. Experimental evaluations assessed changes in wet packing density, workability, mechanical properties, resistance to chloride ion penetration, and heavy metal leaching at various graphite tailings replacement rates (0 %, 25 %, 50 %, 75 %, and 100 %). The microstructural properties of UHPC were analyzed using techniques such as X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Thermogravimetric Analysis (TGA), Mercury Intrusion Porosimetry (MIP), and Scanning Electron Microscopy (SEM). Results indicate that increasing the replacement rate of graphite tailings leads to a gradual decrease in UHPC workability. At a 50 % replacement rate, graphite tailings enhance the wet packing density, contributing to a 7.33 % increase in the 28-day compressive strength. Additionally, graphite tailings can decrease the carbon emissions associated with unit compressive strength by up to 6.96 % and reduce production costs by 20 %. The inclusion of graphite tailings also improves the resistance of UHPC to chloride ion penetration and reduces the leaching of heavy metal ions from the tailings. Microstructural analyses indicate that graphite tailings promote hydration reactions in UHPC without altering the types of hydration products. Additionally, these tailings improve the pore structure of the composite. This study investigates the feasibility of using graphite tailings as a substitute for river sand in the production of UHPC, providing foundational insights for subsequent studies focused on optimizing eco-friendly UHPC formulations that incorporate graphite tailings.