Reuse of copper slag in high-strength building ceramics containing spodumene tailings as fluxing agent

The recycling of industrial side streams is of interest for a sustainable use of resources and from an environmental perspective. This paper deals with the reuse of copper slag and spodumene tailings in the development of ceramic materials for potential application in construction. Copper slag included fayalite and magnetite as crystalline phases while spodumene tailings (quartz-felspar sand, QFS) mainly consisted of albite, quartz and microcline. Kaolin (10 wt%) was added as green strength increasing agent in some compositions and the prepared formulations were sintered between 950 and 1150 degrees C at 50 degrees C intervals. The phase composition was studied by scanning electron microscopy and X-ray diffraction using Rietveld refinement. Tests such as compressive and flexural strength, water absorption, apparent density and freeze thaw cycles were used to assess the material performances. The results showed that densification and strength development were mainly due to partial melting of QFS particles at 1050-1100 degrees C, leading to water absorption in the range 0.5-7 %. At 1100 degrees C, a high-performance compressive strength of 140 MPa was achieved with the formulation made fully of recycled materials (50 wt% copper slag and 50 wt% QFS) suggesting its suitability for high strength demanding materials such as load bearing bricks; values of ultrasonic pulse velocity and compressive strength of these ceramics remained stable after 200 freeze thaw cycles, demonstrating their potential suitability as construction materials in severe weathering environments. Additionally, the leaching test proved a good encapsulation of heavy metals in these ceramics. These results are of interest for waste management and efficient use of resources.