Effect of BaO and Na2O on the viscosity and structure of blast furnace slag

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.