Preparation of β-belite using liquid alkali silicates

Abstract

The aim of this study is the preparation of β-belite by a solid-state reaction using powdered limestone, amorphous silica and liquid alkali silicates. The raw materials were blended, the mixtures were agglomerated and then burnt. The resulting samples were characterized by X-ray diffraction analysis and scanning electron microscopy. Free lime content in the β-belite samples was also determined. The effects of CaO/SiO2 ratio (1.6-2.1), burning temperature (800-1400 °C), utilization of different raw materials (silica fume, synthetic silica, potassium silicate, sodium silicate, potassium hydroxide) and burning time (0.5-16 h) on free lime content and mineralogical composition were investigated. The purest β-belite samples were prepared from a mixture of powdered limestone, silica fume and liquid potassium silicate with a ratio CaO/SiO2 = 2 by burning at temperatures between 1100 and 1300 °C for more than 2 h. Decreasing of the CaO/SiO2 ratio led to rankinite formation and lower a burning temperature led to the formation of wollastonite.