Manufacture of sustainable fired shale bricks using sewage sludge as raw material

This paper assessed the use of shale collected from western China and the incorporation of sewage sludge for manufacturing fired shale bricks, which could reduce the environmental impact produced in the mining process of traditional raw materials. Chemical constituents and mineral composition of shale and sewage sludge were characterized by x-ray fluorescence spectrophotometer (XRF) and x-ray diffractometer (XRD), the analysis indicated that only the shale was a fit bloating material, while the sewage sludge could only be used as additive. Fired shale brick specimens containing 0%-30% (wt) of sewage sludge were fired at temperatures ranging from 920 to 950 degrees C. The tests revealed that with the increase of replacement ratio of sewage sludge, the water content and shrinkage rate increased, whereas plasticity index, bulk density and compressive strength decreased. Comprehensively considering the physical and mechanical properties of specimen, the optimum replacement ratio of sewage sludge and sintering temperature were determined to be 15% (wt) and 940 degrees C, respectively. Scanning electron microscope (SEM) analysis indicated that specimens with sewage sludge contained higher amounts of micropores, which could improve the thermal insulation properties of the specimen. Through the analysis of the experimental results, it could be concluded that the addition of sewage sludge resulted in the successful manufacture of qualified fired shale bricks.