Initial assessment of thermal and mechanical properties of fine-grained processing waste based materials for thermal energy storage applications

Growing demand for efficient and sustainable thermal energy storage (TES) has focused attention on mineral waste as an alternative to natural aggregates. This study investigates the potential use of fine waste fractions from hard coal mining (coal tailings), bottom slag from brown coal combustion, and stone-cutting residues (basalt and marble powders) for sensible heat storage materials. Mixtures were prepared using cement as a binder, alongside additives such as plasticizers and sealing agents. Mechanical (compressive strength) and thermal properties (conductivity, heat capacity, diffusivity) were evaluated, with particular attention to material stability under repeated heating cycles between 50°C and 600°C to simulate operational TES conditions. Results revealed that high carbon content significantly reduces mechanical strength and thermal cycling durability. The slag-based material was excluded from further thermal cycling tests due to its very low compressive strength (1.5 MPa). The coal tailings-based mixture showed the greatest strength reduction after heating (78%), while basalt and marble powder mixtures had a lower, comparable reduction (~55%). Overall, marble powder-based samples demonstrated the highest mechanical and thermal performance, suggesting that selected mineral wastes can be effectively utilized in TES applications, aligning with sustainability and circular economy objectives.