Using white cement as a source of calcium oxide in Anorthite body

Abstract

Anorthite is a rare compositional variety of plagioclase. This mineral is a type of calcium-rich plagioclase feldspar which has great properties such as low thermal expansion coefficient and high modulus of rupture. Therefore, physical properties of hard porcelain bodies will be improved by creating anorthite phase. According to limitation of anorthite natural sources, various sources were used to synthesis of anorthite. In this paper, white cement was introduced as a new calcium oxide source to reach anorthite phase. For this purpose, a standard composition for hard porcelain was prepared by addition of 50 wt% kaolin, 25 wt% potassium feldspar and 25 wt% quartz. Six additional body mixtures were formulated partially by replacing 0, 3, 4.5, 6, 7.5 and 9 wt% of potassium feldspar by white cement. The linear shrinkage, water adsorption, modulus of rapture (M.O.R), and bulk density of fired body were calculated. Phase characterization was accomplished by X-ray diffractometer (XRD) and scanning electron microscopes. By replacing potassium feldspar with white cement, anorthite was appearance in fired body at 1250 °C. This replacing decreases bulk density, linear shrinkage and modulus of rapture. Although, water adsorption and consequently firing temperature increase by replacing white cement but 1250 °C was a good temperature for firing replaced bodies.