Abstract: Municipal solid waste incineration (MSWI) bottom ash represents a promising precursor for alkali-activated cementitious materials, owing to its abundant supply and high content of reactive Si, Ca, and Al. However, effective pretreatment is mandatory to manage its inherent heavy metals and soluble salts. The hydration mechanism of this type of cementitious material is a process dominated by an alkaline environment. The hydration degree is synergistically tunable by the ash fineness, alkali activator type, and supplementary cementitious materials. Research demonstrates that optimizing the ratio of activators to composite systems can enhance mechanical performance, while suitable pretreatment improves durability against freeze-thaw and sulfate attack. The alkali-activated system also ensures environmental safety by efficient immobilizing heavy metals via gel-based physical encapsulation and chemical bonding. Rational matching of the activator system, the bottom ash characteristics and the auxiliary cementitious materials is pivotal for tailoring the setting time to ensure the success of its practical application. However, key research bottlenecks still persist, particularly concerning the synergistic mechanisms of composite activators, detailed reaction pathways and microstructural evolution remain unclear, alongside a lack of systematic investigation into long-term durability of materials and their performance evolution under real service conditions.

Key words: municipal solid waste incineration bottom ash, alkali-activated cementitious materials, hydration mechanism, mechanical properties, durability, heavy metal solidification