## 3 Results
Moreover, a similar \begin{table}
\begin{tabular}{c c} \hline
**Reactive Mixtures** & **Temperature (\({}^{\circ}\)C)** \\ \hline A\_S1 & \\ B\_S1 & 1086 \\ C\_S1 & \\ A\_S2 & 1221 \\ B\_S2 & 1226 \\ C\_S2 & 1203 \\ A\_S3 & 1230 \\ B\_S3 & 1231 \\ C\_S3 & 1231 \\ \hline \end{tabular}
\end{table} 
Table 2: Temperature of the onset of the appearance of the liquid phase. Figure 6: Liquid vs. temp. content and chemical compositions of the liquid phase from FactSage calculation in wt.% of the reactive mixtures containing components of the cement-free corundum-spinel refractory castable with 7 wt.% of MgO (castable C) and steel slags with the C/S mass ratio of 1.1 (**a**), 3.5 (**b**), 5.5 (**c**). situation should be expected for the reactive mixtures A_S1 and B_S1. For the C_S1 reactive mixture, a violent decrease in CM2A8 content is observed from 1350 \({}^{\circ}\)C (Figure 5) because of the total liquid phase formation (Figure 4a). Additionally, a decrease in the MA and C2 AS phases was also observed. A similar tendency should be accepted for the reactive mixtures A_S1 and B_S1. The occurrence of the total liquid phase shown in Figure 4a-c is mainly associated with calcium-aluminates and calcium-aluminate-silicates phases. As the temperature rises from 1250 \({}^{\circ}\)C to 1650 \({}^{\circ}\)C, the initially formed calcium (i.e., at a temperature below 1250 \({}^{\circ}\)C) aluminates CA and CA2 in the reactive mixtures C_S2 and C_S3 (Figure 4b,c); calcium aluminum silicate C2 AS gehlenite in the reactive mixtures C_S1, C_S2, and C_S3 (Figure 4a-c); calcium aluminum silicate CAS2 anorthite in the reactive mixture C_S1 (Figure 4a) gradually decreased. This violent increase in the content of the liquid phase vs. temperature is shown in Figure 6. At 1250 \({}^{\circ}\)C, this increase is mainly due to the presence of C2 AS and CAS2 in the C_S1 sample (Figures 4a and 6a). For samples C_S2 and C_S3, a shift in the appearance of the liquid phase towards higher temperatures was observed. Above the temperature of 1450 \({}^{\circ}\)C in sample C_S2 (Figures 4b and 6b), this increase is mainly caused by CA2, C2 AS, and CA; in sample C_S3 (Figures 4c and 6c), it is mainly associated with the CA, C2 AS, and CA2 phases. It is also worth mentioning that the liquid phase content reached 43.71, 2.38, and 1.38 wt.% at 1350 \({}^{\circ}\)C and 64.24, 7.83, and 16.83 wt.% at 1450 \({}^{\circ}\)C in the reactive mixtures C_S1, C_S2, and C_S3 (Figure 6), respectively. In the FactSage calculation program, it was possible to distinguish the first appearance of a liquid phase at particular temperatures. This summary is presented in Figure 6. To distinguish the onset temperature for the formation of the liquid phase, the individual reactive mixtures in the temperature range 1086-1230 \({}^{\circ}\)C are shown in Table 2.  
We can therefore determine a relationship between the type of slag and the first amounts of the liquid phase formed. As shown in Tables 1 and 2, the temperature at which the appearance of the first amount of liquid phase is determined by the C/S mass ratio. Specifically, it was observed that the onset temperature for the formation of the liquid phase decreased with a decreasing C/S mass ratio in all investigated reactive mixtures. The average temperature values reached ca. 1231 \({}^{\circ}\)C, ca. 1217 \({}^{\circ}\)C, and ca. 1086 \({}^{\circ}\)C for castables A, B, and C with slags S3, S2, and S1, respectively (Table 2). This can be directly related to the presence of the CAS2 in the C_S1 only, while in the reactive mixtures C_S2 and C_S3, this phase was not calculated. Discussing the schematic diagram showing eutectic temperature (Figure 7), it can be easily concluded that CAS2 causes the formation of a liquid phase at 1400 \({}^{\circ}\)C in the presence of C2 AS and 1425 \({}^{\circ}\)C in the presence of MA [38]. Figure 7: Schematic diagram presenting eutectic temperatures between binary and ternary compounds prepared based on Refs. [37; 38; 40; 44; 45; 46; 47].