Mineralogical and chemical characterization of CDW as function of particle size and thermal treatments for potential recycling

Abstract

Construction and Demolition Waste (CDW) originating from the rubble produced by the 2016 seismic events in the Marche Region (Central Italy) has been studied, focusing on its mineralogical and chemical characteristics, to investigate its recycling potentials as a component for eco-sustainable building material or in the glass industry. The aim was to obtain a full characterization of the behaviour of this material at high T in order to determine the most advantageous conditions for vitrification, considered as an effective process for volume reduction as well as for immobilization of potentially hazardous elements. Vitrification experiments, carried out with thermal treatments as function of temperature/duration/particle size and aimed at amorphization, were carried out under atmospheric conditions, at different temperatures (1000-1250°C) and durations (2-8 hours). The study demonstrated that mineralogical composition remains homogeneous for grainsize <4 mm, thus suggesting that no sieving is necessary for recycling of the fine fractions, which are the most difficult to treat. Vitrification, although not achieved for the CDW sample up to 1250°C, due to high-Ca and low-Si contents, demonstrated that this CDW can produce an interesting refractory material and a porous/insulating material. However, experiments showed that full vitrification can be easily achieved by mixing urban waste glass and CDW, suggesting applications in the glass industry. Based on the chemical and mineralogical features of the products, other significant upgrading alternatives of recycling the CDW in different fields of applications are highlighted.