## 3 Results and Analysis
### Analysis of Flexural Strength  
In road pavement, flexural strength is the most basic variable in identifying material properties and is a factor for measuring strength. In road pavement, compressive strength performance and flexural strength performance are the most basic factors in determining the physical properties of materials. It is well known that cement-based composites have excellent compressive strength but are very weak in flexural strength and have low deformability. In this study, as indicated in Table 4, in order to measure the flexural strength of the ECM under the same mixing conditions, the fiber contents were changed by 0.25% to 0.25, 0.5, 0.75, 1.0 and 1.25% in volume fractions to prepare specimens. Figure 10 features a graph showing the average flexural strength measurement results according to the fiber contents of ECM mixed with CF and SF compared to PM. In Figure 10, the average flexural  
Figure 9: Surface temperature distribution in the ECM captured by an infrared thermal camera at 30 V and 40 mm: (**a**) PM, (**b**) ECM-SF25, (**c**) ECM-SF75, (**d**) ECM-SF125, (**e**) ECM-CF25, (**f**) ECM-CF50, (**g**) ECM-CF75, (**h**) ECM-CF100, (**i**) ECM-CF125.  
strength of PM was measured to be 3.76 MPa, and as the contents of CF increased, the flexural strength did not always increase but increased and thereafter decreased. When CF was overused, it was difficult to disperse evenly within the cement matrix and became bundled, resulting in a decrease in flexural strength. In particular, in the case of the ECM-CF125 specimen mixed with 1.25% CF, the flexural strength decreased rapidly. This signifies that when a large amount of CF is mixed, this causes a decrease in flexural strength because the dispersibility and workability are not good due to the fiber balling phenomenon. Multiple repeated mixing introduces a large number of air bubbles and may create many pores within the cement matrix. These findings have also been reported in previous studies [40]. The average flexural strength of all specimens except for the PM and ECM-CF125 specimen mixed with CF was 4.5 MPa or more, and it turned out to satisfy the flexural strength requirements currently applied in the standard specifications for road construction in the Republic of Korea. On the other hand, SF demonstrated an excellent effect on improving the flexural strength, and the average flexural strength of the ECM-SF125 specimen mixed with SF was improved by about 96% or more compared to the PM specimen. It is believed that this is because, as the content of SF increases, it acts as a bridging effect between the fiber and the matrix to prevent crack propagation and improves the flexural strength through the redistribution of stress. However, as the content of SF increased, the flexural strength significantly improved, but when 1.25% was mixed, the dispersibility of the fibers decreased due to fiber balling, and it tended to decrease slightly. In addition, in self-heating cement-based composites, microcracks may occur due to a difference in temperature between the inside and the outside owing to heat generation, and such microcracks can reduce the heating performance. It is, thus, believed that the incorporation of SF enhances the durability of cement-based composites because it has the effect of preventing microcracks in addition to the effect of increasing the flexural strength. Figure 11 shows the increase rate of the flexural strength of ECM-CF and ECM-SF specimens in comparison to the PM specimen.  
Figure 10: The effect of fiber contents on the flexural strength of ECM compared to PM: **(a)** ECM-CF vs. PM, and **(b)** ECM-SF vs. PM.