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Setting time and mechanical properties are key metrics needed to assess the properties of municipal solid waste incineration (MSWI) bottom ash alkali-activated samples. This study investigated the solidification law, polymerization, and strength development mechanism in response to NaOH and liquid sodium silicate addition. Scanning electron microscopy and X-ray diffraction were used to identify the formation rules of polymerization products and the mechanism of the underlying polymerization reaction under different excitation conditions. The results identify a strongly alkaline environment as the key factor for the dissolution of active substances as well as for the formation of polymerization products. The self-condensation reaction of liquid sodium silicate in the supersaturated state (caused by the loss of free water) is the major reason for the rapid coagulation of alkali-activated samples. The combination of both NaOH and liquid sodium silicate achieves the optimal effect, because they play a compatible coupling role.

The over-burnt free-CaO(f-CaO) existential state in hot-splashed steel slag is understood by observing the microstructure of steel slag section and analyzing the minerals in the steel slag (SS). In the investigation, a new method of using hydrochloric acid as the solvent to modify the steel slag powder (SSP) is put forward. The effects of hydrochloric acid pretreatment on the surface morphology of SS and the hydration activity and soundness of SSP blended cement are investigated. Furthermore, the failure mechanism of steel slag cement-based materials and the hydration mechanism of acid-activated steel slag (ASS) are discussed in detail. The research indicated that the optimum dosage of modified SSP is 20 wt%. At this dosage, the 7-and 28-day compressive strength of paste is nearly increased 15% compared with the untreated steel slag cementbased mortar specimens. Moreover, the acid activated SS-blended cement pastes show much better soundness performances after autoclaved curing tests when compared with corresponding pastes with SS without treatment. It provides a promising approach for efficient and safe utilization of SS as supplementary cementitious material.