# Experimental Investigation of TR-UHPC Composites and Flexural Behavior of TR-UHPC Composite Slab
## 2 Axial Tensile Performance of TR-UHPC
### Results and Analyses of Axial Tension Tests
#### 2.3.3 Impact of Textile Reinforcement Ratio on Tensile Properties of TR-UHPC Composites  
For the sake of discussion, the critical textile reinforcement ratio of BFT should first be confirmed. It was assumed that there was no relative sliding between the fiber textile and the matrix before cracking of the UHPC matrix, namely, the fiber textile and UHPC matrix coordinated well in deformation. If the tensile strength of the TR-UHPC composite is expected to increase, the ultimate load of the inside fiber textile should be greater than the cracking load of the TR-UHPC composite. Considering the critical state, the formula for calculating the critical textile reinforcement ratio can be obtained:  
\[\sigma_{cra}=E_{f}\epsilon_{ct}V_{f}+E_{c}\epsilon_{ct}\Big{(}1-V_{f}\Big{)} \tag{1}\]  
\[\sigma_{fu}V_{fmin}=\sigma_{f}V_{fmin}+\sigma_{ct}\Big{(}1-V_{fmin}\Big{)} \tag{2}\]  
\[V_{fmin}=\frac{\sigma_{ct}}{\sigma_{fu}+\sigma_{ct}-\sigma_{f}} \tag{3}\]  
where \(\sigma_{cra}\) denotes the initial cracking stress of the TR-UHPC composite; \(E_{f}\) and \(E_{c}\) represent the modulus of elasticity of the fiber textile and UHPC matrix, respectively; \(\epsilon_{ct}\) represents the matrix cracking strain; \(V_{f}\) represents the textile reinforcement ratio; \(\sigma_{fu}\) represents the ultimate strength of the fiber textile; \(V_{fmin}\) represents the critical minimum textile reinforcement ratio; \(\sigma_{f}\) denotes the stresses applied to the textile of the composite in the critical cracking state, and based on the assumption that the textile and matrix deform together before cracking, \(\sigma_{f}=E_{f}\epsilon_{ct}\); \(\sigma_{ct}\) represents the matrix cracking stress.  
Figure 6 depicts the stress-strain curves of the tensile specimens with various BFT textile reinforcement ratios.  
The critical textile reinforcement ratio of BFT is 0.36%. The T-B2 textile reinforcement ratio in this paper was 0.25%, which is close to the calculated critical textile reinforcement ratio and did not clearly show strain hardening characteristics after cracking. Compared with the T-U specimens, the T-B2 specimens had increases in their initial cracking strength and tensile strength of 12.0% and 16.0%, respectively. Furthermore, the descending stage of  
Figure 6: Comparison of the test results of different textile reinforcement ratios.  
the stress-strain curve of T-B2 was stable at a higher stress level, even though there was only one principal crack. The textile reinforcement ratio of T-B4 was 0.50%, which is greater than the critical textile reinforcement ratio. After cracking, T-B4 showed an obvious strain hardening stage. Additionally, the T-B4 specimens had a multi-cracking pattern compared to T-B2. The ultimate strain of T-B4 was 1.42%, which is about 1.4 times that of the T-B2 specimens, and 2.6 times that of the T-U specimens. The plummet in stress in the T-B series curves resulted from the rupture of the fiber bundles. After the fiber rupture, the T-B series specimens could also resist a high level of stress until failure.