Effect of sintering temperature on the characteristics of sludge ceramsite

In order to investigate the effect of sintering temperature on the characteristics of sludge ceramsite and find an optimal sintering temperature, dried sewage sludge, clay, and water glass were mixed at ratios of dried sewage sludge/clay = 33% and water glass/clay = 15%. Then these mixtures were heated to 850, 900, 950, 1000, 1100, and 1200 °C for production of sludge ceramsite. The sludge ceramsite were characterized by DTA-TGA, SEM-EDS, XRD, and XRF. The results indicate that the differences in thermal behaviours are caused by the compositional and structural variations; the ceramsite sintered at 1000 °C has more uniformly distributed finer pores (0.5 μm < pore size < 10.0 μm), while the ceramsite sintered at other temperatures has less pores and rougher surfaces. The main crystalline phases of ceramsite are quartz and kyanite below 1000 °C; kyanite is the main crystalline phase at 1000 and 1100 °C, and most of the crystalline phases are mullite at 1200 °C. It is therefore concluded that sintering temperature has a significant effect on the characteristics of sludge ceramsite, and that 1000 °C is the optimal sintering temperature.