Soda-lime-silica-glass/quartz particle size and firing time: Their combined effect on sanitary-ware ceramic reactions and macroscopic properties

This paper describes how soda-lime-silica (SLS) glass particle size in combination with firing time and quartz particle size influence sanitary-ware ceramic reactions (mullite/glass formation rate and activation energy), and affect some relevant ceramic bodies' macroscopic properties (water absorption, WA; linear thermal expansion, α; linear shrinking, LS). The study is focused on the system kaolinite, quartz (d50 = 28 and 4 µm), Na-feldspar and SLS-glass (d50 = 35, 23 and 16 µm). SLS-glass in partial replacement of Na-feldspar accelerates the mullite formation rate and the same effect is achieved by decreasing the quartz-d50, which leads to a higher reactivity of the starting slip and to a lesser vitrification grade. In general, mullite formation rate increases with a decrease in SLS-glass-d50. Secondary mullite occurs more abundantly and better shaped in samples with small quartz and SLS-glass d50-values. The technological properties here considered exhibit a complex dependence on SLS-glass/quartz particle size and firing time; in general, they result more sensitive to the former than to the latter. The issues of this work show that one can (i) notably tune WA−α−LS as a function of SLS-glass/quartz particle size and firing time cycle, and (ii) achieve a 30-90 K lowering of firing temperatures (curbing CO2-emissions), making it possible to tailor a reuse of SLS-glass as a function of final ceramic targets.