Bulk Composition Effects on Vitrification of Mixed Fine Construction–Demolition and Inorganic Solid Waste

Abstract

Re-use of neglected and frequently landfilled wastes, including earthquake-generated rubble, can reduce the environmental impact of such waste materials, avoiding georesource exploitation, and potentially provide a source for new upcycling applications. Here, the fine fraction (<0.125 mm) of different wastes was selected according to chemical composition (mostly silicate/oxide-rich materials), including construction and demolition waste (CDW), commercial glass, ceramic industry waste and incinerator bottom and fly ashes. Mixtures of these materials were used for vitrification experiments conducted at atmospheric pressure, 1200 °C, 8 h duration, preparing ten mixes containing 30 to 70 wt% of different waste materials added to a CDW starting material. X-ray powder diffraction and SEM/electron microprobe analyses show that the amorphous content (glass) varies from a maximum of 100 wt.% in products made of CDW with 70 wt.% added ceramic materials (e.g., roof tile) to a minimum of ~53 wt.% amorphous material when CDW was mixed with 30 wt.% brick powder. Mixtures of other waste materials (commercial glass, bottom/fly ash, ceramic waste) produced variable amounts of amorphous component, interpreted in terms of thermal minima in the CaO-Al2O3-SiO2 system. Lack crystallinity and characteristic microstructures of experimental products suggest that vitrification is a promising choice for rendering inert chemically complex waste materials like CDW for possible upcycling applications.