Effects of sintering temperature on the characteristics of lightweight aggregate made from sewage sludge and river sediment

The primary goal of this research is to evaluate the effects of sintering temperature on the characteristics of lightweight aggregate (LWA) made form sewage sludge (SS) and river sediment (RS). The results indicate that LWA made from SS and RS mixed at ratios of 1:1 and sintered at approximately 1100 °C has good physical characteristics with bulk and grain density of approximately 836 kg m−3 and 1672 kg m−3 respectively. The attained compressive strength is 13.7 MPa, water absorption is less than 12% and the fine pores (5 μm < pore size < 15 μm) are uniformly distributed on the surface of LWA. The major mineral phases are quartz, albite and hematite at sintering temperatures above 900 °C. High sintering temperature also promoted the binding capacity of Cd, Cr, Cu and Pb in LWA, and the leaching contents of heavy metals did not change at temperatures above 1050 °C even when the LWA bodies were broken. Therefore, solidification effectiveness of heavy metals can be guaranteed in the LWA. This study demonstrates that it is feasible to use SS and RS as raw materials for making LWA, the sintering temperature is one of key factors to determine the characteristics of LWA, and 1100 °C is regarded as the optimal sintering temperature.