Structure, viscosity, and crystallization of glass melt from molten blast furnace slag

Molten blast furnace slag (BF slag) was modified using liquid-liquid mixing method for glass ceramics preparation, and the structure and viscosity of glass melt after modification were investigated. The BF slag proportion increased from 52.72 wt. % to 67.05 wt. %, and CaO/(SiO2 + Al2O3) also varied from 0.33 to 0.47. The structure of BF slag melt after modification was investigated using Si-29 and Al-27 MAS NMR spectra. With increasing CaO/(SiO2 + Al2O3), the amount of Q(1) remarkably increased while that of Q(2) decreased significantly. Specifically, when CaO/(SiO2 + Al2O3) was more than 0.38, Q(3) disappeared in glass melt. The viscosity of glass melt with CaO/(SiO2 + Al2O3) of 0.47 exhibited a steep change at 1169 degrees C, which was mainly caused by the sufficient crystallization of gehlenite confirmed by DTA cooling analysis, XRD, and FE-SEM-EDS analysis.