Chemical and physical characterizations of dried and pulverized sewage sludge/clay as lightweight aggregates

This paper presents findings on the use of sewage sludge generated from sewage treatment plant (STP) as artificial material in a lightweight aggregates-making process. The chemical and physical characterization of the dried sewage sludge (DSS) and clay were investigated by varying the clay proportion (0%, 10% and 20%) to-DSS and heating temperatures (1020°C to 1100°C). The major components observed in the pulverized sludge were quartz SiO₂, hematite Fe₂O₃, Al₂O₃, CaO and P₂O₅ and small amount of MgO and K₂O were also identified. With 20% clay content at 1100°C sintering temperature, the sintered product exhibited higher compressive strength and the bulk density reduced significantly. Formation of larger pores was confirmed by the SEM images at excessive bloating. In addition, the weight loss increased when the sintering temperature increased and by increasing the sintering temperature and the amount of clay in the sample, a decrease of water absorption was observed. This study shows that the manufactured lightweight aggregate from pulverized sludge is compliant with pertinent standards of lightweight aggregates.