Prediction Model for SiO2 Activity in the CaO-Al2O3-SiO2-MgO Quaternary Slag System

Activity models based on the ion and molecule coexistence theory have been widely used in the refining of metallurgical slags, with the SiO2 content of slag playing a crucial role in improving the mechanical properties of refining slag-based cementitious materials. In order to improve the reactivity of SiO2 in slag, this study established a SiO2 activity prediction model for the CaO-Al2O3-SiO2-MgO quaternary slag system based on the ion and molecule coexistence theory, validating the prediction results using reference values from the literature. Following this, the effects of w(SiO2), w(CaO), w(CaO)/w(Al2O3), and R(w(CaO)/w(SiO2)) on SiO2 activity were explored (where w and R represent content and alkalinity, respectively). The results show that the model could accurately predict the SiO2 activity of refining slag at 1873k. When the SiO2 content was increased from 10% to 30%, with 60% w(CaO) and a w(MgO)/w(Al2O3) ratio of 0.25, the SiO2 activity exhibited a trend of initially increasing and then decreasing, with a maximum activity value of 0.1359 reached at 17.5% w(SiO2). When slag contained 15% w(SiO2) and a w(MgO)/w(Al2O3) ratio of 0.25, the SiO2 activity decreased with increasing CaO content, reaching a maximum activity value of 0.1268 when 55% w(CaO) was present. Therefore, by controlling the ratio of w(CaO)/w(Al2O3) and w(CaO)/w(SiO2) in the slag to maintain a ratio of 3, the activity of SiO2 can be effectively increased.