## 3 Results and Discussion
### Slags Characterization
#### 3.1.2 Mineralogical Characterization and Microstructure  
The mineralogical analyses of the slags are summarized in Tables 3 and 4 for the air and water cooled samples, respectively. The high number of phases detected in each XRD pattern (Figure 1), therefore high overlapping of peaks, made their distinguishing quite difficult and SEM/EDS analysis assisted substantially towards this direction (Table 5). Special care was taken to present selected microanalyses that are either stoichiometric or closely approximate the stoichiometry, since the fractured analyzed surfaces of samples prevented accurate quantitative analyses. Moreover, characteristic microphotographs of their structure obtained by optical microscopy and SEM are presented in Figures 2-5. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**No. (*)** & **Bas. ** & \begin{tabular}{c} **FeO\({}_{\textbf{x}}\)** \\ **(wt.\%)** \\ \end{tabular}  & \begin{tabular}{c} **Al\({}_{2}\)O\({}_{3}\)** \\ **(wt.\%)** \\ \end{tabular}  & \begin{tabular}{c} **MgO** \\ **(wt.\%)** \\ \end{tabular}  & \begin{tabular}{c} **MnO** \\ **(wt.\%)** \\ \end{tabular}  & \ \begin{tabular}{c} **Cr\({}_{\textbf{tot}}\)** \\ **(wt.\%)** \\ \end{tabular}  & \begin{tabular}{c} **S** \\ **(wt.\%)** \\ \end{tabular}  \\ \hline
3-1a, b & 1.68 & 10.7 & 7.72 & 10.8 & 2.48 & 0.53 & 0.29 \\
3-2a, b & 1.32 & 5.32 & 8.57 & 11.5 & 2.51 & 0.60 & 0.30 \\
4-1a, b & 1.50 & 7.30 & 11.6 & 8.93 & 3.12 & 0.96 & 0.36 \\
4-2a, b & 2.61 & 3.85 & 12.00 & 7. Figure 1: _Cont._ \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **3-1b** & **3-2b** & **4-1b** & **4-2b** \\ \hline \(\alpha\)-C\({}_{2}\)S & + & + & + & \\ \(\alpha^{\prime}\)-C\({}_{2}\)S & & & & + \\ \(\beta\)-C\({}_{2}\)S & & & & + \\ C\({}_{3}\)S & + & & & + \\ C\({}_{3}\)MS\({}_{2}\) & + & + & + & \\ C\({}_{3}\)A & + & + & + & \\ C\({}_{3}\)A & + & + & + & \\ C\({}_{12}\)A\({}_{7}\) & & + & + & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Mineralogical phases of water-cooled slags. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **3-1a** & **3-2a** & **4-1a** & **4-2a** & **5a** \\ \hline \(\alpha\)-C\({}_{2}\)S & & + & + & \\ \(\alpha^{\prime}\)-C\({}_{2}\)S & & & + & \\ \(\beta\)-C\({}_{2}\)S & & & + & + \\ C\({}_{3}\)A & + & + & + & + \\ Mg\({}_{1-x}\)Fe\({}_{\rm O}\) & + & + & + & + \\ Spinel & + & + & + & + \\ Chromite & + & + & & \\ C\({}_{4}\)AF & & & & + \\ CF\({}_{2}\) & & & & + \\ CaFeSiO\({}_{4}\) & & & + & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Mineralogical phases of air-cooled slags. Figure 3: (**a**) SEM (SEI) micrograph of MW crystals development in the cubic system; (**b**) micrograph of C4 AF plate crystals development; (**c**) micrograph of hexagonal C3S crystal in the slag matrix; (**d**) micrograph of longwise mervinite crystals development in the slag matrix. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **3-1b** & **3-2b** & **4-1b** & **4-2b** \\ \hline C2 AS & + & + & + & \\ Mg1-\({}_{x}\)Fe\({}_{x}\)O & + & + & + & + \\ Spinel & + & + & + & + \\ Ettringite & + & & & \\ Monosulfate & & & & + \\ \hline \hline \end{tabular}
\end{table} 
Table 4: _Cont._  
Figure 2: (**a**) Image of 35–45-\(\upmu\)m fraction of water-cooled slag under polarized light; (**b,c**) SEM (SEI) micrographs of round-shaped C2S crystals development. According to the obtained results, well-formed crystals were also detected in the slags cooled in water as shown in Figure 1. The constrained amorphous (glass) content was also verified by the optical observation under polarized light of the water-cooled 35-45 \(\upmu\)m slags fraction as indicatively shown in Figure 2a. In order to obtain vitreous granulated slag, as in GGBS, high pressure water jets are required [19]. The main differences in the mineralogical phases identified between air and water-cooled slags of the same chemical composition were the polymorphs of dicalcium silicate attributed to the different rates of cooling.