Effect of Oil Shale Residue on the Hydration of Red Mud-Fly Ash Cementitious Material.

Red mud, fly ash and oil shale residue are all industrial solid wastes with a huge discharging throughout the world, causing serious environmental problems. In this paper, the microstructure of red mud-fly ash blended cement during hydration process was observed by NMR, IR and SEM in an attempt to understand the reaction mechanism of the hydrates mixed with oil shale calcined at 400°C and 700°C. As the reaction progress, the coordination of Al (IV, V, and VI) mostly transfers to IV when the paste mixed with oil shale calcined at 700°C. However, a number of 6-coordinated Al still occur in the hydrated paste mixed with oil shale calcined at 400°C. Under the effect of alkaline, generated from the hydration of clinker, a certain amount of Si and Al atoms are dissolved or hydrolyzed from aluminosilicate to generate geomonomers in solutions and then polycondense to form networks. It is indicated that the distortion degree of [SiO4] and [AlO4] tetrahedra play a significant role during hydration process. [ABSTRACT FROM AUTHOR]