Sintering behaviour of a glass obtained from MSWI ash

The sintering behaviour of a glass obtained by Municipal SolidWaste Incinerator (MSWI) bottom ash (WG) was investigated and compared with a Na2O–MgO–CaO–SiO2 composition (CG). The sintering activation energy, Esin , and the energy of viscous flow, E, were evaluated by dilatomeric measurements at different heating rates. The formation of crystalline phases was evaluated by Differential Thermal Analysis (DTA) and X-Ray Diffraction (XRD), and observed by Scanning Electron Microscopy (SEM) and Transition Electron Microscopy (TEM). In CG, the sintering started at ≈1013 dPa s viscosity and Esin (245 kJ/mol) remains constant in the measured range of shrinkage, up to 9%. In WG the densification started at ≈1011 dPa s, Esin resulted to be 395 kJ/mol up to 5% shrinkage, 420 kJ/mol at 8% and 485 kJ/mol at 10% shrinkage. The sintering rate decreased due to the beginning of the pyroxene formation and the densification stopped in the temperature range 1073–1123K after formation of 5 ± 3% and 13 ± 3% crystal phase, at 5 and 20 K/min, respectively. Higher densification and improved mechanical properties were obtained by applying the fast heating rate, i.e. 20 K/min.