## 3 Results and Analysis
### TGA Analysis  
TGA analysis is a way to continuously measure and analyze the weight change of a specimen while heating it at a constant temperature increase rate. TGA curves can be graphed, and the temperature at which components are decomposed by heat can be analyzed. Cement-based composites contain many hydration products by the hydration  
Figure 11: Percentage increase in flexural strength of ECM compared to PM: (**a**) ECM-CF vs. PM and (**b**) ECM-SF vs. PM.  
Figure 12: SEM images of specimens for 1.25% carbon fiber and 1.25% steel fiber: (**a**) ECM-CF (500\(\times\)), (**b**) ECM-CF (100\(\times\)) and (**c**) ECM-SF (50\(\times\)).  
reaction of cement, and these hydration products change their crystal structure according to the change in temperature and absorb or release energy when they change. According to previous studies, cement-based composites release free pore water and gel water at 100 \({}^{\circ}\)C or higher with respect to heat and are chemically deteriorated at 300 \({}^{\circ}\)C or higher. Within the range of about 450 to 550 \({}^{\circ}\)C, calcium hydroxide (Ca(OH)\({}_{2}\)), the main component of cement, is decomposed by heat, and then dehydration is accelerated, and at about 600 to 700 \({}^{\circ}\)C or higher, calcium carbonate (CaCO\({}_{3}\)) is decomposed. It is known that complete dehydration and decomposition of cement paste finally occur above 700 \({}^{\circ}\)C [41; 42]. In this study, the change in thermal weight was observed while increasing the temperature range of PM and ECM samples from 20 \({}^{\circ}\)C to 980 \({}^{\circ}\)C. Figure 13 is a graph showing the thermogravimetric analysis of the specimens before and after the heating performance test. As seen in Figure 13, the weight loss of the PM samples and the ECM samples is a slight decrease in the weight of the samples due to the evaporation of free pore water within the temperature range from 65 \({}^{\circ}\)C to 250 \({}^{\circ}\)C, but the weight loss tended to increase significantly as the temperature rose from 250 \({}^{\circ}\)C to 700 \({}^{\circ}\)C. It became obvious that calcium hydroxide (Ca(OH)\({}_{2}\)) and calcium carbonate (CaCO\({}_{3}\)) which are major hydration products within the cement matrix were decomposed by heat, resulting in a rapid decrease in the samples' weight. Finally, when the temperature of the samples becomes higher than 700 \({}^{\circ}\)C, one can find that the cement paste experiences complete decomposition and the weight loss does not increase significantly. Furthermore, the increase from 700 \({}^{\circ}\)C to 980 \({}^{\circ}\)C shows a tendency to decrease the amount of loss compared to the case of rising from 250 \({}^{\circ}\)C to 700 \({}^{\circ}\)C. In the case of ECM mixed with SF, however, there is a tendency for the temperature to rise slightly after a rapid drop to 750 \({}^{\circ}\)C. This is thought to be the result of the debonding and oxidation of SF. As a result of dehydration of calcium hydroxide (Ca(OH)\({}_{2}\)) and decarboxylation of calcium carbonate (CaCO\({}_{3}\)), in Figure 13, it can be seen that the phase change of the cement hydration products before and after the heating performance test was not significant.