Optimization of Sustainable Alkali Activated Municipal Solid Waste Incinerator Bottom Ash Materials with High Performance

In general, municipal solid waste incinerator bottom ash (IBA) is mainly utilized as fillers in nonstructural concrete products due to its low reactivity. In this study, the high-strength alkali-activated materials (AAMs) using high calcium IBA was developed. A ternary contour diagram was introduced to optimize the composition of thermally activated IBA (TMBA), ground granulated blast furnace slag (GGBS), and fly ash (FA) in AAMs. The result showed that a high concentration of calcium ions in the ternary system contributed to the provision of nucleation sites for the precipitation of products, thus leading to the promotion of hardening. The optimal compressive strength (80-85 MPa) of AAMs was achieved using 60%-80% GGBS content, 10%-40% TMBA content, and 0%-10% FA content. The AAMs showed high resistance to sulphate attack, chloride penetration, and freeze-thaw when the TMBA content was less than 40%. This was attributed to a dense pore structure formation promoted by the presence of calcium minerals (anorthite, wollastonite, mayenite and gehlenite) as indicated in the X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM) analysis. The embodied CO2 index of the AAMs was about 59%-87% lower than cement, and it was a cleaner cementitious material.