The influence of different CaO source in the production of anorthite ceramics

The effects of starting raw materials and firing conditions on anorthite (CaAl2Si2O8) phase formation are investigated by differential thermal analysis (DTA)–thermogravimetry (TG) and X-ray powder diffraction (XRD). Four different sources of CaO were used for anorthite production such as Ca(OH)2, CaCO3, marble powder and gypsum mould waste. The mixture of raw materials was prepared in stoichiometric ratio of anorthite. Sintering of samples was carried out at various temperatures (1000–1300 °C). In all samples before the formation of anorthite phase, formation of layered alimunosilicate phase (LAS) and of gehlenite phase were observed at low temperatures (<1200 °C). All the samples showed similar crystallization behaviour at 1200 °C. The densification characteristic and the flexural strength of samples were affected by the nature of starting raw materials. The maximum density (∼80%) was reached in sample ACH which was prepared from Ca(OH)2.