Effects of CaO/MgO Molar Ratio on Microstructure and Mechanical Properties of Silicate Glass-ceramics

Silicate glass-ceramics were prepared by adding 40 wt% granite wastes. The effects of CaO/MgO (C/M) molar ratio on microstructure and mechanical properties of glass-ceramics were investigated. With C/M ratio increasing, the crystallization behavior changed from bulk crystallization to surface crystallization with heat treatment at 800 °C. However, bulk crystallization occurred in all samples when crystallized at both 850 and 900 °C. The content of forsterite and tainiolite initially increased and then decreased, while diopside and kalsilite increased when heated at 850 °C. For 900 °C, the increase of C/M ratio promoted the precipitation of diopside rather than forsterite and tainiolite, and interlocked plate crystals abundantly appeared with C/M ratio ≥ 0.14. The values of Vickers hardness for samples crystallized at 850 and 900 °C increased initially followed by a decrease, while the values of fracture toughness showed the opposite trend. The glass-ceramic with C/M ratio 0.065 heated at 900 °C showed relatively high Vickers hardness ((5.7 ± 0.14) GPa) and excellent fracture toughness ((3.55 ± 0.14) MPa·m1/2).