Effect of BaO and Na 2 O on the viscosity and structure of blast furnace slag

Abstract

The effects of BaO and Na₂O on the viscosity and structure of CaO–SiO₂–MgO–Al₂O₃-based blast furnace slag were investigated using the rotating cylinder method and Raman spectra technique in this work. The results indicated that the slag viscosity first increased and then decreased with the addition of BaO and decreased with the increasing content of Na₂O. When adding BaO into CaO–SiO₂–MgO–Al₂O₃ slag, Ba²⁺ ion could compensate Al³⁺ ion and form more complex aluminate or aluminate–silicate structures, which increased the degree of polymerisation and the viscosity of the slag. With the further addition of BaO, the content of SiO₂ decreased and the relative content of O²⁻ ion increased, which may slightly depolymerise the slag structure then decreased the viscosity. When adding Na₂O into CaO–SiO₂–MgO–Al₂O₃–BaO slag, Na₂O may act as network modifiers which could simplify the complex silicate structures and lower the polymerisation degree of slags, therefore decreased the viscosity.