Solidification of Heavy Metals in Waste Incineration Fly Ashes with Silica-Alumina Composite

This paper replaces the ordinary Portland cement with water-quenched granulated blast furnace slags (WQGBFSs), a silica-alumina composite, for solidification of waste incineration fly ashes (WIFAs), and explores the solidification effects of solidified bodies cured for different ages of heavy metals under the excitation of sulfates. The test blocks were subjected to analysis through X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and thermogravimetry and differential scanning calorimetry (TG-DSC). The results show that the silica-alumina composite outshines the ordinary Portland cement in solidification of heavy metals like Pb and Cd; the test block containing 15 % WIFAs, 70 % WQGBFSs and 15 % flue gas desulfurization gypsum (FGDG) reached the compressive strength of 43.67MPa after being cured for 28d, and had much lower leaching concentrations of heavy metals (e.g. Pb, Cd, Hg and Cr) than the limits in the drinking water standard; the main hydration products of the cementitious system are the calcium silicate hydrate (C-S-H) and ettringite (Aft); the hydration products have strong solidification effects of heavy metal ions.