High-Strength Lightweight Artificial Aggregates from Municipal and Industrial Wastes

Abstract Urbanization and industrialization generate increasing municipal and industrial waste, and converting these wastes into construction aggregates can reduce environmental burdens and conserve natural resources. Municipal solid waste incineration fly ash (MSWIFA), red mud (RM), ground granulated blast furnace slag (GGBS), and phosphogypsum (PG) were upcycled into high-strength lightweight artificial aggregates under air, seawater, steam, and CO 2 curing at different temperatures and CO 2 concentrations. X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and backscattered election–energy-dispersive spectroscopy (BSE-EDS) analysis show hydration-driven microstructural development dominated by calcium chloroaluminate hydrate, ardealite, and calcium aluminum silicate hydrate gels, while CO 2 curing mainly enhances carbonate crystallinity. Elevated temperature and moisture accelerate early-age hydration, humid curing enhances gel formation, and steam curing or higher CO 2 concentration increases gibbsite. Seawater curing achieves the highest cylinder compressive strength of 30 MPa and shows lower Pb and Zn leaching than air curing. Together, these results demonstrate the feasibility of converting municipal and industrial wastes into high-strength lightweight aggregates.