Experimental research on mechanical and impact properties of ceramsite prepared from secondary aluminum dross and municipal solid waste incineration ash

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Abstract With the growth of the industrial aluminum smelting sector, and the increasing proportion of incineration treatment in the field of waste management and disposal, there has been a corresponding increase in the production of secondary aluminum dross (SAD) and municipal solid waste incineration fly ash (MSWIFA) annually. In this research, ceramsite is prepared using SAD, MSWIFA, and municipal solid waste incineration bottom ash (MSWIBA) as raw materials. This study explores the impact of various factors on the mechanical properties of ceramsite and their mechanisms under different conditions, including sintering temperature, raw material ball particle size, raw material silica-alumina ratio, and sintering time. Single-factor experiments demonstrate that the compressive strength of ceramsite initially follows a non-linear ascending trend with increasing sintering temperatures. Additionally, the strength is enhanced with reductions in particle size of the raw material balls, prolongation of the sintering time, and a reduction in the silica-to-alumina ratio of the raw materials. Orthogonal experiments reveal the ideal preparation conditions for ceramsite as follows: a preheating temperature of 400 °C, a preheating duration of 20 min, a sintering temperature of 1270 °C, and a duration of 30 min. Under these conditions, the optimal composition ratio of ceramsite is Si:Al = 3, and the ideal particle size is 0.5 cm. Analysis through X-ray diffraction and scanning electron microscopy revealed the formation of new mineral phases such as sodium feldspar and potassium feldspar in the ceramsite, which display a dense structure under microscopic observation. These contribute positively to the mechanical properties of the ceramsite. Fourier-transform infrared spectroscopy analysis indicates that at a sintering temperature of 1260 °C or when the raw material ball size is 2 cm, the [SiO4] tetrahedral bands shift to higher wavenumbers, enhancing the degree of polymerization of the glass network in the ceramsite, thereby strengthening its compressive strength. As the silica-alumina ratio of the raw materials decreases and the sintering duration extends, the [SiO4] tetrahedral bands continue to shift to higher wavenumbers, further enhancing the compressive strength of the ceramsite.