Sintering characteristics of ceramsite manufactured from blast furnace slag and sewage sludge

Abstract

To develop a method of recycling solid wastes, blast furnace slag (BFS) and sewage sludge (SS) were added as components for making ceramsite. This study examined the sintering characteristics of ceramsite at different sintering temperatures and duration and different mass ratios of materials (BFS:SS:clay). The results show that as the sintering temperature and duration increased, the pore-size diameter gradually increased, reaching a maximum of 120 nm at 1100°C for 20 min. The turning point for the pore-size diameter was at 1050°C for 20 min. In keeping with the variation in pore-size diameter, the highest and lowest porosity of the ceramsite reached 88 and 62%, respectively. The different mass ratios of three raw materials (BFS, SS and clay) had no significant effect on the thermal behaviors of the ceramsite, with the DT-TG analysis curves showing essentially the same trends in terms of variation. As the sintering temperature increased, the complex crystalline phases appeared at 900°C, while no variation occurred within the main crystalline phases except for the transformation from akermanite (Ca 2 MgSi 2 O 7) to gehlenite [Ca 2 Al(AlSiO 7)] at 1050°C.