# Experimental Study of the Thermal and Dynamic Behaviors of Polypropylene Fiber-Reinforced Concrete
## 5 Conclusions  
In this study, polypropylene fiber-reinforced high-performance concrete (HPC) was made using local materials in Kunming, Yunnan Province, China. Since high-strength HPC has been widely studied, this research focused on low-strength HPC. Three types of concrete--C30, C40, and C50--were made and a number of HPC specimens were produced in order to test the dynamic and thermal behavior of the polypropylene fiber-reinforced concrete. The split Hopkinson pressure bar (SHPB) was employed for the dynamic tests and the principles of the SHPB were introduced in detail. An electric resistance furnace was employed to heat the samples while insulation measures for the specimens during the test were taken to maintain stable temperatures. Then, the polypropylene fiber-reinforced HPC was taken under the coupled various loading rates with different high-temperature treatments. It is concluded that the temperature significantly influences the HPC fracture patterns. During the SHPB test with the same air pressure (1.2 MPa) in the gas gun, many fractures were produced in the specimen with a 100 \({}^{\circ}\)C temperature treatment. However, it was not smashed into fragments. For the other specimens heated to higher temperatures from 200 \({}^{\circ}\)C to 800 \({}^{\circ}\)C, the specimens were smashed into fragments. The main reason for this is that the melting point of the polypropylene fiber is 165 \({}^{\circ}\)C.  
It can be seen from the stress-strain curves of the specimens that the dynamic compressive strength of the concrete specimens increase with the increase in the strain rate at the same temperature.  
The temperature can influence the HPC strength. At temperatures lower than 300 \({}^{\circ}\)C, the HPC's compressive strength increases with increases in temperature. At temperatures higher than 300 \({}^{\circ}\)C, the HPC's compressive strength decreases with increases in temperature.  
Conceptualization, H.A. and L.L.; methodology, H.A. and L.L.; formal analysis, H.A. and L.L.; investigation, Y.W. and L.D.; writing--original draft preparation, H.A. and Y.F.; funding acquisition, L.L. All authors have read and agreed to the published version of the manuscript.  
This work was partly supported by the National Science Foundation of China (Grant no. 11862010), Research Start-Up Fund for Talent of Kunming University of Science and Technology (Grant no. KSFY201867017), Program for Innovative Research Team (in Science and Technology) in University of Yunnan Province, Funding from the Research Center for Analysis and Measurement KUST (Analytic and Testing Research Center of Yunnan, Grant number 2020T20180040), Yunnan Key Laboratory of Sino-German Blue Mining and Utilization of Special Underground Space, Guizhou Provincial Department of Education Natural Science Research Top-notch talents Project (Y[2020]041), Guizhou High-level innovative talents training project (2016-21), which are greatly appreciated.  
Not applicable.  
The data used to support the findings of this study are included within the article.  
The authors declare that there are no conflicts of interest regarding the publication of this paper.