Stabilization and Solidification of Fine Incineration Bottom Ash of Municipal Solid Waste Using Ground Granulated Blast-Furnace Slag

The fine incineration bottom ash (IBA) is usually landfilled due to its high heavy metal content and low strength. In this study, the fine IBA was stabilized/solidified by a green binder, ground granulated blast-furnace slag (GGBS), as a potential subbase material for road construction, in comparison with the traditional binder, ordinary portland cement (OPC). Specimens of untreated IBA, OPC-IBA, and GGBS-IBA with different binder contents were prepared. The concentrations of leached heavy metals (lead, zinc, cadmium, chromium, copper, and nickel), unconfined compressive strength (UCS), as well as mineral composition and microstructure of specimens were investigated. The results showed that the concentrations of heavy metals leached from GGBS-IBA was lower than those from untreated IBA and OPC-IBA, satisfying regulated limits for construction materials. The UCS of GGBS-IBA was 8.5–14.8 times higher than that of untreated IBA and 1.3–2.1 times higher than that of the corresponding OPC-IBA. Lime and portlandite in IBA were consumed to activate the hydration of GGBS, facilitating its strength development. IBA and GGBS complemented each other, i.e., IBA activated the GGBS hydration and increased the strength, while GGBS immobilized heavy metals in IBA, preventing them from leaching out.