## 4 Results and Discussion  
### Relevance of Methodology  
The concentrations of the major constituents in the original slag are presented in Table 4. As previously stated, prior to water granulation, the slag undergoes a reduction process to remove zinc. Since the reduction progress to partial pressures of oxygen close to the reduction of ferrous iron to metallic iron, the analysis in Table 4 is presented as ferrous iron rather than ferric. The chemical composition of the sample is within normal variations at the smelter, and, as such, it represents a viable choice for evaluating the relevance of the developed method. As evident from the comparison of Tables 3 and 4, the composition of the synthetic slags was intentionally designed to deviate from the industrial slag. The basis for the synthetic triplicate sample was the wider operational window for calcium oxide and alumina, outside the scope of a single smelter, in accordance with the widespread compositions reported in the literature and illustrated in Figure 7. However, the FeO/SiO\({}_{2}\) ratio was placed at the lower end of the spectrum to maintain the relevance for the specific smelter of the present study, which still complies with several previously studied slags. Furthermore, the data highlights, once more, the need for a methodology to generate slags that can be compared on a fair basis. As outlined in Section 1, the origin of the slags in Figure 7 differs in terms of cooling conditions, degree of crystallinity, composition, and grinding. \begin{table}
\begin{tabular}{c c} \hline \hline
**Component** & **Concentration [wt.\%]** \\ \hline FeO & 46.2 \\ SiO\({}_{2}\) & 40.7 \\ CaO & 2.9 \\ Al\({}_{2}\)O\({}_{3}\) & 5.2 \\ MgO & 1.3 \\ ZnO & 1.2 \\ Cu & 0.8 \\ Na\({}_{2}\)O & 0.7 \\ K\({}_{2}\)O & 0.6 \\ S & 0.3 \\ Cr\({}_{2}\)O\({}_{3}\) & 0.2 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Normalized chemical composition of the sample (note roundoff error to 100.1%). \begin{table}
\begin{tabular}{c c} \hline \hline
**Component** & **Concentration [wt.\%]** \\ \hline FeO & 47.50 \\ SiO\({}_{2}\) & 39.72 \\ Ca\(\O\) & 5.63 \\ Al\({}_{2}\)O\({}_{3}\) & 4.97 \\ MgO & 1.99 \\ Cr\({}_{2}\)O\({}_{3}\) & 0.19 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Theoretical composition of synthetic slags. Studies assessing iron silicate complex slags for SCM applications show substantial crystallization of, e.g., fayalite [10; 11; 12; 17; 18; 20], magnetite [10; 11; 17; 18; 19; 20], monticellite (possibly misevaluated kirschsteinite) [17], hedenbergite [18], and calcium sulfate dihydrate [18]. If the aim is to evaluate the effect of chemical composition, the cooling procedure must generate an amorphous slag since only a few crystalline phases show pozzolanic behavior [46]. More specifically, crystalline materials other than, e.g., zeolites and certain minerals in calcareous fly ashes can be considered inert [28; 46; 47]. Another effect of crystallization is that the overall chemical composition of the slag no longer represents the reactive amorphous phase, which further complicates the intended comparison. The diffractograms of the original slag and the three slags granulated on a laboratory scale are presented in Figure 8. The figure illustrates that the laboratory scale granulation successfully generated an amorphous material for all three temperatures, which shows that laboratory scale granulation is a relevant cooling method for the slag. Another parameter varying between previously published studies on iron silicate slags is the grinding procedure and, subsequently, the resulting particle size distribution. [PERSON] et al. [24] summarized that the fineness of SCMs has been suggested to be of more importance for reactivity than the SCMs' chemical compositions. Therefore, comparing different chemical compositions requires the absence of crystallization in combination with similar specific surface areas of the materials.