## 4 Results and Discussion
### Robustness of Methodology  
In Section 4.1, the relevance of this methodology was proven, showing that slags granulated on a laboratory scale had similar reactivity as the same slag granulated on an industrial scale. Since the main idea of the present study was to find a method for enabling controlled studies on the effect of changes in chemical composition on reactivity, the repeatability of the synthesis procedure was evaluated. Figure 10 presents the analyzed chemical composition of the triplicate sample. In addition, the theoretical concentrations are included for comparison. The figure illustrates that the concentrations of the major components compare well to the aimed composition. Furthermore, the standard deviation of the population was calculated to be 3.6, 3.6, 2.7, 2.4, and 4.3% of the average value for iron(II) oxide, silica, calcium oxide, alumina, and magnesia, respectively. Therefore, the repeatability of achieving the desired concentrations was considered satisfactory. The minor component, i.e., chromium(III) oxide, was analyzed for 0.12, 0.10, and 0.13 wt.% for samples A, B, and C, respectively, which was less than the aimed concentration of 0.19 wt.%. The low chromium(III) oxide content was considered less important for the subsequent evaluation. More specifically, since the procedure managed to incorporate chromium into the slag, the formation of chromium-rich spinel phases may be facilitated, which satisfies the intended role of chromium in the system. Based on the diffractograms recorded with internal standards (Figure 11), the three slags were entirely amorphous. Therefore, the intended composition of the slag was successfully incorporated into the amorphous phase, which suggests that synthetic samples suitable for comparing the effect of chemical composition on the reactivity were generated. Furthermore, the chromium content did not facilitate the nucleation and crystallization of phases within the detection limit of the equipment used in the present study. These results are consistent with the results of the industrial slags presented in Section 4.1. For the industrial slag, grinding generated consistent specific surface areas. However, for samples A, B, and C, the surface areas were measured to be 0.544, 0.418, and 0.474 m\({}^{2}\)/g, respectively. Laser diffraction was performed to further assess the differences, and the results (Figure 12) suggested that the grinding successfully produced similar particle size distribution curves. Therefore, based on the specific surface areas, which were consistent with the d\({}_{50}\) values, the comminution progressed differently between samples. Possibly, the slight variations in chemical composition (Figure 10) could affect the grindability of the slags, especially for increased iron contents. Since the reaction rate depends on the surface area [24], the grinding procedure can be iterated to produce similar granulometric characteristics, which allows for a better comparison of the reactivity in the calorimetry-based testing. However, utilizing a standardized grinding process in the present study was based on the previously reported non-breakage effects introduced by grinding [55]. Figure 11: Diffractograms of triplicate samples (denoted A, B, and C) including calcite as internal standard. Figure 10: Concentrations of (**A**) FeO and SiO\({}_{2}\), as well as (**B**) CaO, Al\({}_{2}\)O\({}_{3}\), and MgO in the synthetic samples compared to the theoretical values. Comparing Figures 9A and 13A, the progression of the recorded heat follows a similar pattern, i.e., an initial high reaction rate followed by a kink and, finally, the progressive depletion of the slags from continuous dissolution and reaction. This similarity suggests that the reaction mechanisms of the synthesized slags are not different from the industrial slag. Based on the fact that the synthetic slags successfully integrated the components in an amorphous phase, the observations on the reaction pattern are expected.