Fluidized bed combustion ash utilization: CFBC bottom ash as a cementitious material

Two methods employed to reduce sulfur dioxide emissions from the electricity generation are flue gas desulfurization (FGD) and circulating fluidized bed combustion (CFBC). The quantity of sulfated byproducts from these technologies will likely increase substantially over the next several years. This study focused on utilizing FGD gypsum, CFBC ash and Class F fly ash for the production of low-energy, 100% byproduct cement. There were two main components of the cement: calcium sulfate hemihydrate and a blend of CFBC spent bed material and Class F fly ash. At the outset of the study there were two potential problems identified: slow strength gain and destructive expansion during hydration. Blending calcium sulfate hemihydrate with CFBC ash and fly ash produced a 100% byproduct cement that achieved satisfactory early strength and was dimensionally stable. However, the calcium sulfate component remains an impediment towards long-term durability because of its high solubility.