Sintered glass-ceramics from incinerator fly ashes. Part II. The influence of the particle size and heat-treatment on the properties

A composition obtained by mixing MSW ashes with sand and glass cullet was melted at 1500 °C and quenched in water. The obtained frit was sieved and separated in different fractions: L (large, 2–5 mm), I (intermediate, 1–2 mm) and S (small, <1 mm). The sintering of the glass particles, carried out in an alumina mould, occurred in the 700–950 °C range. The curve of the crystal growth rate as a function of the temperature was obtained by means of 1 h heat-treatment in the 850–1050 °C range. The crystal growth started at 850 °C and the maximum rate, 0.013 mm/min, occurred at 1020 °C. The ferrobustamite crystal phase was evaluated by XRD analysis and observed by optical microscopy. The mechanical, thermal and chemical properties of the L, I and S glass-ceramics were measured and discussed. They resulted to be influenced by the grain size of the glass particles and by the percentage of crystal phase.