## 3 Experimental Results and Discussion
### Flexural Strength and Residual Flexural Strength
Comparing the serviceability limit expressed by \(f_{R1k}/f_{Lk}\), presented in Table 6, FF8 was the only composite that satisfy the requirement to prevent brittle failure in structural member proposed by the _fib_ Model Code 2010 (\(f_{R1k}/f_{Lk}\geq 0.4\), and \(f_{R3k}/f_{R1k}\geq 0.5\)). The residual flexural strength \(f_{R1}\) of FF8 increased by 69% when compared to FF4, while \(f_{R2}\), \(f_{R3}\), and \(f_{R4}\) doubled, evidencing the fiber contribution post-cracking. In contrast to FF8, batches FF4 and FF6 did not satisfy the first requirement to prevent brittleness failure (\(f_{R1k}/f_{Lk}\geq 0.4\)). However, the results obtained for the \(f_{R3k}/f_{R1k}\) indicate the effectiveness of the fibers bridging up to the ultimate limit state at CMOD3. Table 7 shows that the gradual increase in fiber content increases the composite post-cracking performance from CMOD1 to CMOD4. This is corroborated by the \(f_{R3k}/f_{R1k}\) ratio, presented in Table 6, clearly indicating the effect of the fiber dosage, i.e., it increases the ultimate performance of the composite. As discussed by [PERSON] [35], in plain concrete crack bridging is provided by aggregate locking action. When fibers are added to concrete, additional bridging action is brought into effect, superimposing on the aggregate bridging effect. It should be recognized that at the formation of a matrix crack, and prior to any crack opening, the fiber is already in a stressed state. Thus, the combined crack bridging mechanisms depends on the individual contributions of the aggregate bridging action, the fiber bridging action, and the fiber prestress. Indeed, the fiber content plays a significant role in the bridging action observed in the post-cracking stage. As observed in results presented in Tables 5-7, \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Batch** & \(f_{Lk}\) & \(f_{R1k}\) (**MPa**) & \(f_{R3k}\) & \(f_{R1k}/f_{Lk}\) & \(f_{R3k}/f_{R1k}\) \\ \hline FF4 & 4.88 & 1.42 & 1.44 & 0.29 & 1.01 \\ FF6 & 5.50 & 1.27 & 1.33 & 0.23 & 1.05 \\ FF8 & 4.51 & 2.49 & 2.83 & 0.55 & 1.14 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Summary of the 28-day characteristic values of all batches according to the _fib_ Model Code 2010. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Batch** & \(r_{L}\) & \(r_{1}\) & \(r_{2}\) & \(r_{3}\) & \(r_{4}\) \\ \hline FF4 & 1.00 & 1.00 & 1.00 & 1.00 & 1.00 \\ FF6 & 1.13 & 1.01 & 1.31 & 1.26 & 1.22 \\ FF8 & 0.95 & 1.69 & 2.00 & 1.98 & 1.96 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Flexural strength ratio (\(r_{j}\)) of all batches compared to FF4. the fiber content has not directly increased the SCC flexural strength but has significantly affected the post-cracking performance of the composites. [PERSON] and [PERSON] [36] further describe the mechanism of fracture resistance for fiber-reinforced concrete in three stages: (i) The subcritical crack growth in the matrix and the beginning of the fiber bridging effect; (ii) the post-critical crack growth in the matrix, where the fiber-bridging closing stresses remains constant, and (iii) the final stage, where the resistance to crack separation is provided exclusively by fibers. Figure 5. Fibers bridging the crack shows the fibers bridging the crack at the final fracture stage in the FF8 beam at CMOD4 = 3.5 mm.