# Experimental Study of the Thermal and Dynamic Behaviors of Polypropylene Fiber-Reinforced Concrete
## 1 Introduction  
In recent decades, society has developed faster than ever before in history. The rapid development of society has greatly increased the need for geo-structures, such as tunneling, embankments, bridges, shafts, slopes, and all kinds of buildings for both living and working in. Meanwhile, accidents have occurred from time to time and have caused geo-structures to experience dynamic loading. In some cases, geo-structures have been subjected to both dynamic loading and high temperatures. As concrete is the most widely used building material for geo-structures [1; 2; 3], the dynamic and thermal behaviors of concrete are essential to the stability and durability of geo-structures [4; 5; 6; 7]. As concrete has a low ductility and is very weak in tension, fiber-reinforced concrete has been developed and is employed in many geo-structures [4; 8; 9; 10]. In addition, as the majority of geo-structure accidents--e.g., failures and collapses--are related to fractures produced due to static or dynamic loading, it is important to study the dynamic fracture mechanism of concrete. The split Hopkinson pressure bar (SHPB) might be the most used testing equipment [11; 12; 13; 14; 15] for the study of the dynamic behavior of concrete and rock-like brittle materials. [PERSON] (1941) developed the SHPB by using a pressure bar to test the pulsewaveform; then, it was employed to measure the mechanical properties of rock under dynamic loads [16]. The SHPB can be used to study rock mechanics at strain rates between \(10^{1}\,\sim 10^{4}\) S\({}^{-1}\). Many dynamic tests of concrete and rock-like materials have been conducted by a number of researchers using the SHPB. Among those tests, the uniaxial compression test, the Brazilian disk test, and the semi-disc with the pre-fabricated crack test are recommend by the International Society of Rock Mechanics as standard dynamic experiment methods. [PERSON] et al. (1994) conducted an impact test on cement and studied the influence of the loading rate on the cement strength using the split Hopkinson pressure bar [17]. In addition, [PERSON] et al. (1997) also used the split Hopkinson pressure bar to study the dynamic behavior of ceramic materials and concluded that the loading rates influenced the tensile strength of the materials significantly [18]. [PERSON], [PERSON] et al. (2004) found that specimens subjected to impact loading were found to suffer greater damage than those subjected to static loading [19]. [PERSON] (2000) conducted dynamic uniaxial and triaxial compressive strength tests and concluded that compressive strength increases with an increased loading rate [20]. [PERSON] (2000) also conducted a dynamic uniaxial compressive strength test and concluded that the number of cracks increases with an increasing loading rate [21]. Besides those researchers mentioned above, many researchers have reached almost the same conclusion: the loading rate significantly influences the behavior of brittle materials [19; 20; 21; 22; 23; 24; 25; 26]. The thermal behaviors of brittle materials have been extensively studied. [PERSON] et al. (2010) studied the dynamic and thermal behaviors of siltstone and found that, in the range of 20-100 \({}^{\circ}\)C, the compressive strength increases with increases in temperature, while it decreases with increases in temperature when the temperature is higher than 100 \({}^{\circ}\)C [27]. [PERSON], [PERSON] et al. (2013) studied the properties of granite under dynamic loading and higher-temperature conditions [28]. They found that the peak strain increased with the increase in temperature, while the strength of the granite decreased with the increase in temperature [28]. [PERSON] and [PERSON] (2013) carried out compression experiments with marble and found that when the temperature rises to 800 \({}^{\circ}\)C, the peak strength of marble becomes less obvious with changes in the loading rate. To improve the stiffness of concrete, fiber-reinforced concrete was developed to increase its strength and ductility.