## 3 Experimental Results and Discussion
### Split Tensile Strength  
The experimental results of the split tensile strength of fiber concrete at different strain rates are shown in Figures 6 and 7. Similar to the law of the compressive strength, the addition of PVA can also increase the tensile strength of concrete. In the quasi-static state (i.e., a strain rate of \(10^{-5}\) s\({}^{-1}\)), the addition of PVA significantly improved the tensile strength of FRC compared with plain concrete,  
Figure 5: Fitting curves of compressive strength \(DIF_{c}\) for C30 PVA0.2 and C40 PVA0.2.  
as also seen in previous findings [28]. When the matrix strength of concrete is C30, the growth values are 19.4, 10.9, and 20.3% for fiber volume contents of 0.2, 0.4, and 0.6%, respectively. When it is C40, the growth values are 17, 10.9, and 7%, respectively. The tensile strength of FRC also has a rate sensitivity compared with plain concrete. As strain rate increased, the splitting tensile strength with different contents increased to some extent, while the growth rate increased first and then decreased later, which did not follow the law of the compressive strength. In the low range of strain rates (e.g., \(10^{-5}\) and \(10^{-4}\) s\({}^{-1}\)), the bridging effect of the fiber plays a major role in concrete. At this time, the increase of the tensile strength of fiber concrete depends mainly on the bonding force between the fiber and the cementitious material. As the strain rate increases (e.g., to \(10^{-3}\) or \(10^{-2}\) s\({}^{-1}\)), the increase of the loading rate exceeds the expansion rate of the cracks inside the concrete. Hence, the concrete aggregate is directly cut off, and the bridging effect of the fiber is relatively weakened, resulting in the tensile strength of FRC showing a downward trend, as compared with that of plain concrete. In general, the bridging effect of the fiber plays a major role at low strain rates. With the increase of strain rate, the bridging effect of the fiber is weakened, leading to the change of the concrete fracture form from the destruction of cementitious material under a low strain rate to the direct cut of coarse aggregate a under high strain rate. This is confirmed in the existing literature [30; 31] and shown in Figure 8.  
Figure 6: Split tensile strength of FRC (C30).  
Figure 7: Split tensile strength of FRC (C40).  
According to the fitting method of the dynamic impact factor in the concrete compression experiment, the formula for the dynamic tensile strength of fiber concrete with 0.2% content is established by using polynomial fitting. The fitting formula and curves are shown below, as in Figure 9. From the fitting results, the conclusion that a higher matrix strength is directly related to weaker fiber enhancement is equally applicable to splitting tensile strength. However, unlike the fitting curves of compressive strength, the curves of splitting tensile strength tend to increase first and then decrease. The dynamic impact factor of split tensile strength of fiber concrete reaches the maximum at a strain rate of \(10^{-4}\) s\({}^{-1}\) for both matrix strengths.  
\[DIF_{t}=\frac{f_{t}}{f_{ts}}=1.211+0.0783\lg\left(\frac{\dot{\varepsilon}}{ \dot{\varepsilon}_{s}}\right)-0.0426\left[\lg\left(\frac{\dot{\varepsilon}}{ \dot{\varepsilon}_{s}}\right)\right]^{2}\text{ for C30 PVA0.2} \tag{3}\]  
\[DIF_{t}=\frac{f_{t}}{f_{ts}}=1.1766+0.0087\lg\left(\frac{\dot{\varepsilon}}{ \dot{\varepsilon}_{s}}\right)-0.0139\left[\lg\left(\frac{\dot{\varepsilon}}{ \dot{\varepsilon}_{s}}\right)\right]^{2}\text{ for C40 PVA0.2} \tag{4}\]  
where \(DIF_{t},f_{t}\), and \(f_{ts}\) are the dynamic impact factor of split tensile strength, dynamic split tensile strength, and quasi-static split tensile strength, respectively. \(\dot{\varepsilon}\) and \(\dot{\varepsilon}_{s}\) have the same meaning as previously described above.  
Figure 8: Two kinds of split tensile failure modes of FRC.  
Figure 9: Fitting curves of split tensile strength \(DIF_{t}\) for C30 PVA0.2 and C40 PVA0.2.