## 3 Results
### Compressive Strength  
Figure 4 denotes the relationship between the compressive strength of PPFRC and fiber volume dosage. The lines shown in the figure represent the compressive strength (\(f_{cm}\)) trend based on linear regression for the fiber lengths of 40, 50, and 60 mm. Pearson's correlation coefficients, \(r\), were 0.59, 0.99, and 0.76, respectively, showing medium, very strong, and considerable positive correlations. Here, the trend was more determined when the length \begin{table}
\begin{tabular}{l l l l l l l l l l} \hline \hline
**Type** & \begin{tabular}{l} **Slump** \\ **(mm)** \\ \end{tabular} & \begin{tabular}{l} **\(V_{f}\)** \\ **(\%)** \\ \end{tabular} & \begin{tabular}{l} **\(l\)** \\ **(mm)** \\ \end{tabular} & \begin{tabular}{l} **\(f_{cm}\) (MPa)** \\ \end{tabular} & **CV\%** & \
\begin{tabular}{l} **\(f_{sp}\) (MPa)** \\ \end{tabular} & **CV\%** &
\begin{tabular}{l} **\(f_{r}\) (MPa)** \\ \end{tabular} & **CV\%** \\ \hline Pattern & 99.00 & - & - & 40.27 & 1.38 & 2.55 & 10.36 & 5.79 & 21.78 \\ M1\_04\_40 & 100.00 & 0.40 & 40.00 & 39.64 & 1.83 & 2.82 & 10.83 & 6.20 & 8.19 \\ M2\_08\_40 & 68.00 & 0.80 & 40.00 & 45.15 & 1.33 & 2.75 & 8.50 & 5.81 & 1.75 \\ M3\_12\_40 & 56.00 & 1.20 & 40.00 & 42.74 & 1.88 & 3.08 & 8.44 & 6.39 & 3.48 \\ M4\_04\_50 & 100.00 & 0.40 & 50.00 & 43.97 & 0.77 & 3.10 & 1.96 & 5.23 & 3.29 \\ M5\_08\_50 & 78.00 & 0.80 & 50.00 & 43.02 & 1.43 & 3.15 & 2.40 & 6.40 & 0.60 \\ M6\_12\_50 & 35.00 & 1.20 & 50.00 & 43.89 & 1.53 & 3.42 & 6.69 & 6.14 & 4.44 \\ M7\_04\_60 & 80.00 & 0.40 & 60.00 & 41.49 & 1.47 & 2.50 & 15.93 & 6.01 & 4.04 \\ M8\_08\_60 & 68.00 & 0.80 & 60.00 & 42.63 & 0.47 & 3.15 & 7.97 & 6.28 & 4.66 \\ M9\_12\_60 & 37.00 & 1.20 & 60.00 & 40.93 & 0.75 & 3.45 & 6.34 & 6.49 & 6.29 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Results of the mechanical strengths of concrete. of the fibers was 50 mm. Table 5 shows the results of the \(t\)-test performed between each type of fiber concrete and the standard concrete. The results showed that in no case could the null hypothesis be rejected, which stated that there was no statistically significant difference between the samples. Table 6 denotes the results of [PERSON]'s statistical hypothesis test to reject or not reject the null hypothesis about the correlation between compressive strength and fiber volume. The \(p\)-value for the concrete samples where 40 mm and 60 mm fibers were used was 0.413 and 0.238, respectively. Considering a significance level of 0.100, if the \(p\)-value is greater than the value of the significance level, the possibility of the null hypothesis cannot be rejected. Therefore, the results were not statistically significant in these two types of concrete. On the other hand, the concrete sample with 50 mm fibers had a \(p\)-value of 0.012. Therefore, the null hypothesis was rejected, and the results were statistically significant. This analysis showed that if there was a positive correlation between variables, the greater the volume of fibers, the greater the resistance to compression. However, the hypothesis that the samples were identical could not be rejected statistically. This was because the results between samples were similar. Figure 5 denotes the results of this study when compared with other studies [32; 53; 54; 55; 56]. Several authors have concluded that the addition of plastic macrofibers in low volumes does not have significant effects on compressive strength \begin{table}
\begin{tabular}{l l l l l l l} \hline \hline
**MV** & **IV** & **DV** & \(\mathbf{r}^{2}\) & \(\mathbf{r}\) & \(\mathbf{p}\) & **Null Hypothesis** \\ \hline \(l=40\) mm & \(V_{f}\) & \(f_{cm}\) & 0.344 & 0.587 & 0.413 & no rejection \\ \(l=50\) mm & \(V_{f}\) & \(f_{cm}\) & 0.975 & 0.987 & 0.012 & rejected \\ \(l=60\) mm & \(V_{f}\) & \(f_{cm}\) & 0.581 & 0.762 & 0.238 & no rejection \\ \hline \hline \end{tabular}  
* MV—Moderating variable. IV—Independent variable. DV—Dependent variable.  
\end{table} 
Table 6: [PERSON]’s hypothesis test of the correlation between \(f_{cm}\) and \(V_{f}\).