## 4 Discussion  
### Confined Test Pieces  
Figure 3 shows images of the test pieces once testing was complete. It can be seen that in the six cases the fault type was very similar and occurred due to the fracturing of the fibers under tensile strength. The fracture was preceded by a loud cracking sound before the fiber snapped. The only difference that could be observed was that whilst the fault in the test pieces reinforced with HM (Figure 2(b)) fibers occurred in three test pieces due to the fracturing of fibers throughout the length of the test piece, in the test pieces reinforced with fibers of a lower modulus (Figure 2(a)), this only happened in one of them, whilst in the other two test pieces, the fracturing of the fibers only occurred in the central third. Table 4 shows the breaking strain values, \(\sigma_{r}\), obtained in the compression tests, as well as the average values \(\overline{x}_{\sigma r}\), the typical deviation \(s_{cr}\), and the percentage strength increase \(\Delta_{\sigma r}\) experienced by the reinforced test pieces compared to the benchmark specimens. Figure 2: Diagram of the beams tested and the experiment layout. The results in Table 4 show that both fabrics provide an effective way of reinforcing concrete elements subjected to compression. In both cases, increases in strength of around 50% were obtained compared to the strength of the original element. This value is the maximum recommended by documents which regulate the use of this type of reinforcement system due to their vulnerability when exposed to fire or vandalism [23]. Both types of \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Test Piece** & **Confinement** & \(\mathbf{\sigma_{r}}\)**(MPa)** & \(\mathbf{\widetilde{x}_{or}}\)**(MPa)** & \(\mathbf{s_{cr}}\)**(MPa)** & \(\mathbf{\Delta_{cr}}\)**(\%)** \\ \hline C1 & & 44.6 & & & \\ C2 & Non-confined & 45.1 & 46.5 & 2.93 & - \\ C3 & & 49.9 & & & \\ N1 & & 74.2 & & & \\ N2 & HR & 67.6 & 68.9 & 4.74 & 1.48 \\ N3 & & 65.0 & & & \\ H1 & & 70.0 & & & \\ H2 & HM & 71.4 & 71.5 & 1.55 & 1.54 \\ H3 & & 73.1 & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Results of compression testing: average values, typical deviation, and strength increase. Figure 3: Images of fracturing in the compression-tested pieces. reinforcement delivered practically the same breaking load, despite the huge difference in the rigidity values. This seems to indicate that the decisive factor in the breaking load of the reinforced element is the mechanical capacity of the fiber under tensile strength, irrespective of its rigidity, always within the limits of the elements tested. These data were analyzed using an ANOVA technique. This can help to globally decompose the observed error across all the data (nine samples) into the variance explained by the factor (here formed by three levels: non-confined, HR. and HM) and the variance not explained by the factor. In this way, compared to the separate measurements of mean and standard deviation for each level of the factor, the statistical significance is treated globally (because the null model assumes normally distributed, homoscedastic errors with the same variance for every level of the factor) and therefore turns out to be multiplied by three. Considered together, we can safely reject the null hypothesis of equal averages in the three compression tests performed (ANOVA \(p\)-value: 0.000174). Paired means were also compared via the adjusted ANOVA model. Here, significant differences were found when comparing non-confined and HM treatments (Tukey contrast \(p\)-value: 0.00235) and when comparing non-confined and HR treatments (Tukey contrast \(p\)-value: 0.00431). However, there were no significant differences between the HM and HR treatments (Tukey contrast \(p\)-value: 0.6366). Therefore, it can be stated that confinement of the material significantly increases compression resistance, but there were no differences in strength between both types of analyzed confinement.