Recycling of MSWI fly ash into low-carbon supersulfated composites

Abstract

Recycling municipal solid waste incineration ash (MSWI FA) into value-added construction materials presents a sustainable solution, while facing critical challenges including low-performance of products and potential leachability of potentially toxic elements (PTEs). This work innovatively proposed that recycle MSWI FA as an activator to produce low-carbon and high-performance supersulfated composites (MSSC). Microscopic characterization results revealed the hydration kinetic of MSSC was controlled by ettringite generation. The formed C-S-H in MSSC exhibited fiber-like morphology due to the nucleation and template effects of ettringite nuclei. Unlike conventional solid waste-binders, the designed MSSC formed a unique hydrate network through the overlapping of ettringite, Friedel’s salt and C-S-H, achieving excellent mechanical performance (>72 MPa). Besides, chlorides and PTEs in MSWI FA were strongly immobilized by the formed Friedel’s salt and other hydrates. According to economic and environmental evaluation assessment, the production of such MSSC binder could achieve 8.7 USD/m³ profits and only caused 44.4 kg/ m³ CO₂ emissions. This study expanded the resource utilization approach of MSWI FA and contributed to the construction of zero-waste cities and the achievement of carbon neutrality.