Enhancing the reaction of municipal solid waste incineration (MSWI) bottom ash in blast furnace slag-based alkali-activated blends: A novel strategy and underlying mechanism

Compared with blast furnace slag (BFS), the less reactive MSWI bottom ash (MBA) plays a minor role in alkali-activated blends. This research optimized the use of MBA as a precursor by enhancing its contribution to strength and microstructure development. The proposed strategy combines pre-treatment with pre-activation processes, enabling MBA to react before BFS addition. The NaOH-based pre-treatment led to the oxidation of metallic aluminum and the partial dissolution of the amorphous phase in MBA. The subsequent pre-activation resulted in the generation of C-A-S-H gel, which promoted later-stage gel formation in the paste. The reacted bottom ash particles exhibited distinct features in alkali-activated pastes. Compared with 100 % slag-based system, blending slag with MBA accelerated the slag reaction at late ages and facilitated the formation of a more polymerized C-(N-)A-S-H gel. The compressive strength results indicate that MBA is a promising alternative to Class F coal fly ash in BFS-based alkali-activated blends.