Effect of (CaO+MgO)/SiO ₂ ratio on crystallisation and properties of slag glass–ceramics

Metallurgical slag, quartz sand and coal fly ash were used as the raw materials for preparation of glass–ceramics according to their compositions and characteristics. Under different mole ratios of (CaO+MgO)/SiO2, the crystallisation mechanism, microstructure and main mechanical properties of glass–ceramics were systematically investigated through differential thermal analysis, X-ray diffraction, scanning electron microscopy, mechanical and chemical properties test. The results indicate that MgO plays the same role of CaO. The crystallisation activation energy Ea and crystallisation temperature Tp decrease as the increase in (CaO+MgO)/SiO2 ratio. It is found that when (CaO+MgO)/SiO2 ratio is 0·64 and sintering lasts for 1 h at 996°C, main phase of diopside can be obtained with the best mechanical properties and chemical durability, such as bending strength 110 MPa, microhardness 6·5 GPa, mass loss rate of 0·25 and 0·1% as acid resistance and alkali resistance respectively.