Influence of Al₂O₃/SiO₂ Ratio on Viscosities of CaO–Al₂O₃–SiO₂ Melt

Abstract

The influence of Al₂O₃/SiO₂ ratio on viscosity of CaO–Al₂O₃–SiO₂ melt was investigated by the rotating cylinder method in this study. Three groups of compositions with different CaO contents of 0.35, 0.4 and 0.45 were studied. From the experimental results, it was concluded that viscosity always first increases and then decreases as gradually increasing Al₂O₃/SiO₂ ratio. The appearance of viscosity maximum may be resulted from the opposite variation tendencies of mean bond strength and the degree of polymerization of melt with Al₂O₃/SiO₂ ratio. When substituting SiO₂ by Al₂O₃, the mean bond strength decreases because of the weak Al–O bond relative to Si–O bond, which decreases viscosity; while the degree of polymerization is enhanced by the charge compensation effect of Al³⁺ ion, which increases viscosity. Our new proposed viscosity model can well describe the viscosity variation of CaO–Al₂O₃–SiO₂ melt.