Work

Mechanical and microstructural properties of graphite tailings based geopolymer mortars at high temperature

Year: 2025

Type: article

Abstract: Graphite tailings (GT), a prevalent solid waste, present a viable route for resource recovery when utilized in geopolymer production, aligning with environmental standards while yielding economic benefits. Against this backdrop, this study examines how carbonate minerals (e.g., calcite, dolomite) in GT influence the high-temperature strength of GT geopolymer (GTG) mortar-a property pivotal to its fire resistance, as refractory construction materials must retain fundamental mechanical performance at elevated temperatures to ensure structural integrity. The study aims to identify the optimal mix design to produce GTG mortar that exhibits both excellent mechanical properties and potential fire-resistant applications, Particularly for applications such as fire-resistant partitions, industrial furnace linings, and emergency fire-retardant coatings-where materials are frequently exposed to medium-to-high temperatures (300–1050°C)-both thermal stability and load-bearing capacity are essential requirements. The mass loss, compressive strength, microstructural changes, and thermal stability were evaluated over the temperature range of 25–1050°C. The results indicate that as temperature increased, mass loss progressively rose, while compressive strength demonstrated an initial increase, followed by a decrease, and subsequent recovery. A slight strength improvement was observed at 150°C, attributable to ongoing polymerization of the raw materials, which supports enhanced early-stage fire resistance in low-temperature baking scenarios. Between 600°C and 750°C, the decomposition of carbonate minerals in the aggregates led to a significant decline in mass, compressive strength, and thermal stability. 900°C, strength reaches its nadir yet remains above 15 MPa, providing a foundational basis for high-temperature fire-resistant applications. TG/DSC, XRD, FTIR, and SEM analyses elucidate the microscale mechanisms driving these performance variations, offering a scientific framework for understanding the evolution of high-temperature fire resistance in GTG mortar. The findings advance the practical utilization of GT as sustainable construction materials and provide insights for the valorization of other carbonate-containing solid wastes. • MGGTA mortar performance was tested at room temperature and high temperatures. • MGGTA mortar strength drops initially but rises with increasing temperature. • Between 600°C and 750°C, calcite and dolomite decomposition in GT reduces MGGTA mortar compressive strength. • Late-stage mass loss in MGGTA mortars at high temperatures is mainly due to GT aggregate mass loss.

Source: Case Studies in Construction Materials

DOI: 10.1016/j.cscm.2025.e05388