Microstructure and properties of high-strength lightweight ceramsites customised with ultra-fine copper tailings

Abstract

The accumulation of copper tailings not only consumes a significant amount of land resources but also incurs substantial treatment expenses and causes environmental pollution. This article presents an investigation on the feasibility of utilizing ultra-fine copper tailings (CTs), polishing slag (PS), and fly ash (FA) to produce customised high-strength ceramsites for treating and reusing copper tailings.Additionally, the effects of raw material mass ratio and sintering temperature on the physical properties, thermal properties, chemical structure, and expansion mechanism of the high-strength ceramsites were investigated. The experimental results revealed that the well-formed ceramsites exhibited an apparent density of 486–2304 kg/m3, a bulk density of 288–1659 kg/m3, a 1-h water absorption rate of 0.13–3.9 %, and a particle compressive strength of 0.87–22.4 MPa with copper tailings content of 50∼100 % under preheating temperature 950 ℃ for 40 min and sintering temperature 1195–1225 ℃ for 40 min. The XRD analysis of crystal phases indicated that the mineral compositions of ceramsites contained quartz, anorthite, albite, and mullite. Moreover, the FTIR spectra displayed that [AlO4] and [SiO4] were interconnected into a complementary network which enhanced the strength of ceramsites. Additionally, the microstructure analysis revealed that more evenly distributed and smaller pore structures and rougher matrix were associated with higher compressive strength. The temperature difference between the interior and exterior led to the preferential formation of a slag phase which exerted a bonding effect on the composite feldspar phase. These findings suggest that ultra-finecopper tailings could be recycled in artificial aggregate technology in concrete engineering, and provide theoretical support for the large-scale utilization of tailings.