Upcycling spodumene tailings and waste glass in ceramic tiles production: Effect of particle size fractionation and sintering temperature on the properties

The generation of spodumene tailings, also known as quartz feldspar sand (QFS), has continued to rise worldwide owing to the increasing demand for lithium for various applications, of which approximately 600,000 tons are expected to be generated annually in Finland. To avoid the landfilling of this waste and converting it to a value-added product, this study investigates the upcycling of QFS and waste glass (WG) in ceramic tile production. Furthermore, the characteristics of the different particle size fractions of QFS (75–125 µm and 125–250 µm) were assessed and compared with the as-received and milled QFS. The developed compositions were prepared using as-received QFS (QFS-AS), QFS-75–125 µm, QFS-125–250 µm, and milled QFS-AS (QFS-milled) as the primary precursor. WG was added as a fluxing agent in the compositions and then sintered at 750℃, 850℃, and 950℃ to produce the ceramic tiles. The materials and prepared ceramic tiles were characterized for their physical, chemical, mineralogical, mechanical, microstructural, and durability properties. The experimental results show that the raw materials are environmentally friendly and contain no hazardous elements, with their leaching values below the specified limits stipulated by the European Union regulations. Meanwhile, the tile made of milled QFS (TQFS-milled) exhibited better mechanical, microstructural, and durability properties, ascribed to the milling effect, which enhances its reactivity and promotes better sintering reactions. At 950℃, TQFS-milled achieved the highest flexural strength (13.5 MPa) and the lowest water absorption (5%). However, TQFS-AS, TQFS-75–125, and TQFS-125–250 were less sensitive to the fluxing effect of WG, likely owing to differences in their particle size distribution and chemical and mineralogical composition. All samples remained stable after exposure to acetic acid for 30 days and 138 freeze-thaw cycles in water, indicating their potential suitability as construction materials in aggressive and severe weathering environments.