## 3 Results and Discussion
### Thermogravimetric Analysis (TGA)  
Figure 6 shows the results of TGA of the specimens with C/S molar ratios adjusted by silica fume and quartz powder. [PERSON] (1995) examined the decomposition temperature of cement hydration and reported that C-S-H, ettrine, and monosulfate hydration products decompose in the temperature range of 90 to 200 \({}^{\circ}\)C [24; 25; 26]. Drawing on this finding, it was assumed in this experiment that all mass loss in the temperature range of 90-200 \({}^{\circ}\)C was due to the decomposition of C-S-H-based products, ettrine, and monosulfate hydration products. As shown in Figure 6, the ignition loss in the temperature range of 90-200 \({}^{\circ}\)C increased in proportion to the C/S molar ratio in the mixing design adjusted by quartz powder. This led to the assumption that the specimen with the C/S molar ratio of 0.95 would have the highest C-S-H hydration capacity because it is inversely proportional to absorption rate, and pores are reduced as the optimal conditions for generating C-S-H hydrate are satisfied. However, the specimens with the mixing design adjusted by silica fume showed low ignition loss at a C/S molar ratio range of 0.7-0.9, and high at \(\leq\) 0.6 and \(\geq\) 0.95, regardless of the water-absorption rate. The mix in which the C/S molar ratio was adjusted mainly by silica fume showed different results from the absorption rate results. In specimen 0.95 SF, which does not contain silica fume, the C/S molar ratio was adequate, but the absorption rate increased, presumably due to the lack of fine powders. In specimen SF0.6, with the highest silica fume content, reactivity increased due to the increase in the amorphous silica fume content. In  
Figure 5: Absorption of concrete depending on C/S molar ratio. SF0.6, pores in concrete also increased with an increase in the specific surface area that impeded smooth dispersal, resulting in a disadvantageous water-absorption rate [27]. Figure 7 quantifies the weight loss from dehydration of H2O of C-S-H, ettrinigite, and monosulfate using the DTA curve at 200 \({}^{\circ}\)C or lower, calculated with Equation (2). \[\text{Hydrated Product}[\text{wt}\%]=\frac{\Delta W_{dry,90-200} ^{\circ}\text{C}}{W_{dry,105}\text{C}} \tag{2}\]  
In specimens using quartz powder, the amount of C-S-H increased in proportion to the C/S molar ratio, and the amount of portlandite decreased due to the pozzolanic reaction. In specimens using silica fume, however, an increasing amount of portlandite was generated as the C/S molar ratio increased. These results are assumed to be attributed to a high pozzolanic reactivity of silica fume containing amorphous silica and a low pozzolanic reactivity quartz powder as a crystalline silica material [28]. Generally, during hydration, CH is also produced along with C-S-H; therefore, the two hydrates must have a proportional relationship. In addition, when a pozzolanic material is used, CH is consumed by the pozzolanic reaction; therefore, the amount of CH changes according to the degree of pozzolanic activation. Figure 6: Ignition loss of concrete depending on C/S molar ratio, (**a**) QP, (**b**) SF. Figure 7: Hydrated product content of concrete depending on C/S molar ratio, (**a**) QP, (**b**) SF. Figure 7 shows the amount of C-S-H and CH produced by the specimens cured in an autoclave. Figure 7a shows the data when quartz, a crystalline silica, is used. As the relative amount of QP decreases in the range of C/S molar ratio from 0.6 to 0.9, the amount of CH showed similar values for 0.7 and 0.8, but decreased overall. The amount of C-S-H, a CaO hydrate, showed a slight decrease at C/S molar ratios of 0.6 and 0.7, with values of 18.34% and 17.23%, respectively, but increased as the C/S molar ratio increased from 0.7 to 0.9. However, in the C/S molar ratio range of 0.9 to 0.95, the trend of the two hydrates was reversed. Under autoclave conditions, even crystalline silica can participate in the hydration reaction, and the appropriate range is known to be in the range of 0.8 to 0.9 in terms of C/S molar ratio.