## 2 Experimental Program
### Material Properties  
In the previous study [4], three grades of concrete strength were designed, each with different admixtures and fiber content. The material tests employed a seven-factor and three-level orthogonal design. We considered the properties of economy, durability, and mechanics to determine the best concrete mix ratio for each strength grade, as shown in  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Number** & **Strength Grade** & _d_/mm & _l_a/d** & _c/mm_ \\ \hline C30-16-5d-64 & C30 & 16 & 5 & 64 \\ C30-16-5d-48 & C30 & 16 & 5 & 48 \\ C30-16-5d-32 & C30 & 16 & 5 & 32 \\ C30-18-3d-66 & C30 & 18 & 3 & 66 \\ C30-18-5d-66 & C30 & 18 & 5 & 66 \\ C30-18-7d-66 & C30 & 18 & 7 & 66 \\ C30-18-5d-54 & C30 & 18 & 5 & 54 \\ C30-18-5d-36 & C30 & 18 & 5 & 36 \\ C30-18-5d-27 & C30 & 18 & 5 & 27 \\ C30-20-3d-65 & C50 & 20 & 5 & 65 \\ C30-20-5d-65 & C50 & 20 & 5 & 65 \\ C30-20-5d-20 & C50 & 20 & 5 & 20 \\ C30-20-5d-40 & C50 & 20 & 5 & 40 \\ C30-20-5d-60 & C50 & 20 & 5 & 60 \\ C30-22-5d-64 & C50 & 22 & 5 & 64 \\ C30-25-5d-62.5 & C50 & 25 & 5 & 62.5 \\ C40-14-5d-68 & C40 & 14 & 5 & 68 \\ C40-16-5d-67 & C40 & 16 & 5 & 67 \\ C40-18-5d-66 & C40 & 18 & 5 & 66 \\ C40-20-5d-65 & C40 & 20 & 5 & 65 \\ C40-22-5d-64 & C40 & 22 & 5 & 64 \\ C40-25-5d-62.5 & C40 & 25 & 5 & 62.5 \\ C50-14-5d-68 & C50 & 14 & 5 & 68 \\ C50-16-5d-67 & C50 & 16 & 5 & 67 \\ C50-18-5d-66 & C50 & 18 & 5 & 66 \\ C50-20-5d-65 & C50 & 20 & 5 & 65 \\ C50-22-5d-64 & C50 & 22 & 5 & 64 \\ C50-25-5d-62.5 & C50 & 25 & 5 & 62.5 \\ \hline \hline \end{tabular} Note: The specimen number consists of four parts, namely A, B, C and D. One type of specimen is numbered A-B-C. D, where A represents the strength of hybrid fiber-reinforced concrete, B represents the diameter of reinforcement bars, C represents the relative anchoring length and D represents the minimum protective layer thickness.  
\end{table}
Table 1: _Cont._  
Figure 1: Test specimen.  
\begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline
**Concrete** & **Cement** & **Silica** & **Fyme** & **Fly Ash** & **Slag** & **Water** & **Sand** & **Stone** & **Basalt** & **Polypropylene** \\
**Strength** & **Cement** & **Fyme** & **Fyme** & **Fly Ash** & **Slag** & **Reducer** & **Water** & **Sand** & **Stone** & **Fisher** & **Fiber** \\ \hline C30 & 234.2 & 22.0 & 73.2 & 36.6 & 3.66 & 161.0 & 683.0 & 1162.9 & 1.28 & 0.46 \\ C40 & 241.6 & 15.8 & 79.2 & 59.4 & 3.96 & 150.5 & 683.4 & 1163.6 & 2.56 & 0.00 \\ C50 & 333.1 & 29.0 & 48.3 & 72.4 & 4.83 & 140.0 & 774.1 & 1026.1 & 1.28 & 0.00 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Concrete mix proportions (kg/m\({}^{3}\)).  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Diameter (mm)** & **Yield Strength** & **Tensile Strength** & **Yield Strength** & **Maximum Total** & **Ultimate** \\
**(MPa)** & **(MPa)** & **Ratio** & **Elongation (\%)** & **Elongation (\%)** \\ \hline
14 & 460 & 610 & 0.73 & 15.0 & 29.0 \\
16 & 445 & 600 & 0.74 & 14.5 & 24.0 \\
18 & 465 & 595 & 0.78 & 16.5 & 35.0 \\
20 & 440 & 600 & 0.73 & 14.5 & 24.0 \\
22 & 425 & 570 & 0.75 & 15.5 & 23.0 \\
25 & 435 & 580 & 0.75 & 16.5 & 23.0 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Basic mechanical properties of steel bars.  
Figure 3: Test steel size.  
Figure 2: Test block destroyed forms. (a) C30; (b) C40; (c) C50.