## 4 Conclusions  
In this study, the properties, such as flexural performance, compressive strength, and impact resistance of MFRCM and HyFRCM, were investigated. From the obtained experimental study, the following conclusions can be drawn:  
1. The compressive strength of MFRCM and HyFRCM did not improve significantly compared to PM, whereas the flexural strength showed a high improvement effect of about 60.5-148.5%.
2. The mechanical properties of HyFRCM with high SF content were relatively higher than those with low SF content, and HyFRCM containing 0.75% SF and 0.25% CF featured higher strength and impact resistance than other HyFRCM and MFRCM.
3. Although the flexural strength of HyFRCM containing 0.5% SF and 0.5% CF was slightly low, the maximum effect was exhibited in terms of flexural toughness, and the effect of improving flexural toughness by hybridization of SF and CF could be confirmed.
4. Compared to PM, both MFRCM and HyFRCM significantly improved flexural performance, such as maximum flexural strength, flexural toughness, and equivalent flexural strength. In the case of HyFRCM, the application of equivalent flexural strength is judged to be a rather conservative evaluation since it has a predetermined residual flexural strength and a large amount of flexural toughness even under a deflection of 2.0 mm or more.
5. The flexural toughness test results showed that the average flexural toughness of T600 and T150 in HyFRCM containing 0.5% SF and 0.5% CF was 8.1 J and 32.7 J, respectively. After cracking, flexural toughness was greatly improved, which was the most effective in terms of load-carrying capacity.
6. From the impact resistance test, the number of blows from the first crack to the final fracture of the PM specimen is found to be about 1 to 2, whereas, in the case of MFRCM and other HyFRCM specimens, there was a slight difference depending on the amount of SF and CF incorporated but, HyFRCM specimen incorporated with 0.75% SF and 0.25% CF showed the utmost impact resistance. It is thus believed that the effect of increasing the impact ductility by SF and CF is large.  
Conceptualization, [PERSON]-[PERSON] and [PERSON]-[PERSON]; methodology, [PERSON]-[PERSON] and [PERSON]-[PERSON]; validation, [PERSON]-[PERSON] and [PERSON]-[PERSON]; formal analysis, [PERSON]-[PERSON] and [PERSON]-[PERSON]; investigation, [PERSON] and [PERSON]; writing--original draft preparation, [PERSON]-[PERSON]; writing--review and editing, [PERSON]-[PERSON] and [PERSON]; visualization, [PERSON] and [PERSON]; supervision, [PERSON]-[PERSON]; project administration, [PERSON]-[PERSON]; funding acquisition, [PERSON]-H.H. All authors have read and agreed to the published version of the manuscript.  
This research was funded by Basic Science Research Program through the National Research Foundation of Korea (NRF) of the Ministry of Education, Republic of Korea (Grant no. NRF-2018R1A6A1A03025542).  
Not applicable.  
This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (Grant no. NRF-2018R1A6A1A03025542).  
The authors declare that there is no conflict of interest.