Density Measurements of Low Silica CaO-SiO₂-Al₂O₃ Slags

Density measurements of a low-silica CaO-SiO₂-Al₂O₃ system were carried out using the Archimedes principle. A Pt 30 pct Rh bob and wire arrangement was used for this purpose. The results obtained were in good agreement with those obtained from the model developed in the current group as well as with other results reported earlier. The density for the CaO-SiO₂ and the CaO-Al₂O₃ binary slag systems also was estimated from the ternary values. The extrapolation of density values for high-silica systems also showed good agreement with previous works. An estimation for the density value of CaO was made from the current experimental data. The density decrease at high temperatures was interpreted based on the silicate structure. As the mole percent of SiO₂ was below the 33 pct required for the orthosilicate composition, discrete \( {\text{SiO}}_{4}^{4 - } \) tetrahedral units in the silicate melt would exist along with O^2– ions. The change in melt expansivity may be attributed to the ionic expansions in the order of

Structural changes in the ternary slag also could be correlated to a drastic change in the value of enthalpy of mixing.