Rice husk and sewage sludge co-combustion ash: Leaching behavior analysis and cementitious property

The co-combustion of sewage sludge with rice husk is expected to become a trend because of its economic and environmental benefits. In this work, the ashes and its cementitious forms were investigated. The leachability characteristic of heavy metals and mechanical properties in cementitious forms was evaluated. The stabilization/solidification (S/S) mechanism of cementitious forms was also studied. Results showed that the leachability of heavy metals in co-combustion ashes decreased by an average of 30% after the hydration process. Non-crystal hydrates gradually formed and the compact structure hydrates became apparent in RSCA30 after 28 d (relative to SSMA30 and OPC1). The chemical speciation of heavy metals is transformed into immobilization state after hydration. In general, ashes from the co-combustion of rice husk and sewage sludge are beneficial to the development of cementitious materials.