Effects of fly ash vitrified slag (FVS) dosage and alkali content on the reaction of alkali-activated material (AAM)

Alkali activated materials (AAMs) are regarded as a favorable alternative to cement. Ground granulated blast-furnace slag (GGBS) is a common AAM material. Municipal solid waste incineration fly ash vitrified slag (FVS) is derived from the high-temperature vitrification of municipal solid waste incineration fly ash (MSWI FA) at 1200-1500 degrees C. A novel AAM is proposed using municipal solid waste incineration fly ash vitrified slag (FVS) to substitute part of GGBS as precursors. The effects of varying FVS dosage and alkali content on the hydration mechanism, working performance, and microstructure of the AAM were explored. Experimental results indicate that blending GGBS with FVS results in a delayed induction period and reduced overall hydration heat release due to FVS addition, while increasing the alkali level can accelerate the induction period and enhance the total hydration heat release. Blending GGBS with FVS has a beneficial impact on the extent of reaction and properties of fresh pastes, including fluidity and setting time. Although FVS addition lowered the overall strength, using 50 wt% FVS resulted in a high compressive strength of over 80 MPa and low porosity of 15.8244 % after 28 days of curing. Increasing the alkali content was also conducive to strength development and pore refinement, as confirmed by porosity and microstructural analysis. However, excessive alkali concentration have adverse effects. The use of 50 wt% FVS dosage and 4 % alkali content is recommended as a tradeoff between performance, economics, and sustainability.