Ultra-lightweight ceramsite prepared from coal-biomass co-combustion ash and retired photovoltaic glass: Microstructure and sintering characteristics

Promoting the resource utilization of industrial solid waste is vital for achieving low-carbon development. Leveraging the high silicate content in coal-biomass co-combustion ash (CBCA) and retired photovoltaic glass (RPVG), this study utilized the co-sintering method to prepare ultra-lightweight ceramsite. The effects of raw material ratio, sintering parameters, and silicon carbide (SiC) addition on the characteristics and microstructure of the ceramsite were investigated, along with the assessment of CO 2 emissions. The optimal performance was obtained by sintering at 1150 °C for 15 min with 80 wt% CBCA to 20 wt% RPVG. During sintering, the amorphous phase and quartz in the raw materials melted to form liquid phase, which trapped gases generated by the high-temperature oxidation of SiC to facilitate pore formation. Concurrently, silicates in the liquid phase reacted with aluminum, sodium, calcium, and magnesium ions to crystallize into albite, anorthite, and diopside, which enhanced the mechanical properties of the ceramsite. Controlled addition of SiC promoted foaming reaction and pore formation, but excessive additions of SiC reduced the structural stability. Under the optimal sintering conditions, the ceramsite with 2 wt% SiC addition exhibited the bulk density of 0.46 g/cm 3 , apparent density of 1.06 g/cm 3 , compressive strength of 9.06 MPa, and 1h-water absorption of 3.73 %. This study demonstrates the feasibility of using CBCA and RPVG to prepare the ultra-lightweight ceramsite with reduced CO 2 emissions, offering an eco-friendly solution for solid waste valorization and green construction applications.