Utilization of river sediment, sewage sludge and wheat straw as the primary raw material in sintered-shale bricks

China produces large amounts of sewage sludge and agricultural waste every year. In line with the concepts of economic and environmental sustainability, the disposal of these wastes has become increasingly urgent. This paper proposes a feasible way to use river sediments, sewage sludge, and wheat straw as raw materials for sintered shale bricks. The critical processes of best humidity conditions, molding pressure, and sintering temperature were studied and analyzed to determine the optimal production parameters. Moreover, the physical and mechanical properties were investigated to assess their suitability as a partial replacement for the shale in fired-shale bricks. The results showed that moist mixtures with the maximum dry density, the molding pressure of 2 MPa, and a sintering temperature of 1050 celcius were the optional condition to sinter high-quality bricks. Overall, the mechanical strength of bricks tended to slightly decrease with the 10-30% substitution of shale by river sediments, which showed a sharp fall with the 1-3% incorporation of sewage sludge and wheat straw, implying that massive organic matters could enhance the porosity of bricks during the sintering process. The bulk density, thermal conductivity coefficient, and drying shrinkage tended to decrease, whereas water absorption increased as three raw materials increased. Additionally, the sewage sludge and wheat straw have a positive inhibiting effect on the sintering shrinkage due to the expansion burned from massive organic matter. At the replacement level of 10-30% river sediments, 1-2% sewage sludge, and 1% wheat straw, bricks with the characteristics of low thermal conductivity, lightweight, and high strength were successfully manufactured according to the Chinese Standards.