## 5 Flexural Capacity and the Load-Displacement Relationship
According to Figure 19, reducing shear rebars' spacing to 100 mm led to dropping the impact of SFs on the bending performance of the RCARC beams. Furthermore, raising the RCA contents generally led to an increased deformation; however, adding SFs did not have a momentous effect on the maximum flexural capability. On the other hand, providing enough shear rebars caused an improvement in the bending performance of specimens. Therefore, crack propagation increased and the crack widths decreased. Furthermore, the first crack loading increased when increasing the RCA content. Hence, using SFs in RC beams that were manufactured with sufficient shear rebars (100 mm spacing) only reduced the crack widths and there was no significant influence of the structural performance of the RC beams. However, when insufficient shear rebars (200 mm spacing) were used, using SFs not only limited the crack widths and their propagation but also improved the structural performance of RC beams. According to Figures 15, 17 and 19, in addition to increasing the bonding between the rebars and the concrete, cracks developed less after adding SFs due to the bridging role of the fibres and the improvement of the bond-slip between the rebars and the concrete because, with the reduction of the slip between the concrete and rebars, the crack widths were lower. Therefore, specimens with 2% SFs deformed with more ductility and did not collapse abruptly. In specimens with no SFs, the crack propagation was much shorter than in those with SFs. In contrast, in beams with SFs, the final crack spacing corresponding to the stabilised cracking phase was on average 23% smaller than that of the specimens with no SFs. According to these outcomes, it became clear that the formed cracks were consistently much more irregular in beams with SFs than in those without. The crack spacing's variation ratio ranged from 14 to 39% in beams with no SFs, and from 39 to 46% in specimens with SFs. The relationship between the maximum and average crack spacing was a momentous factor too. This relation was 1.60 in specimens with no SFs and 1.74 in specimens with SFs. To study the effect of RCA and SF contents as a function of the shear rebars' spacing, the crack spacing at the peak loads are presented in Table 5 and Figure 20. In Figure 20, the enclosed area of the polygons indicates the influence of the variables on the crack spacing. This means that a reduction of the enclosed area shows a reduction of the crack widths and the positive influence of SFs. Furthermore, in Table 5, the corresponding cracking loads are shown. According to Table 5, using SFs resulted in a considerably decreased crack width at the peak load. Contrariwise, using RCA with more broken surfaces led to a better aggregate bond with cement than using NCA. Therefore, this resulted in reducing the crack widths and increasing the flexural capacity. Providing enough shear rebars along the specimens' length was essential, especially in specimens with shear cracks, but using SFs could dramatically control the effect of the lack of shear rebars in terms of a reduction in the crack widths. Regarding Figure 20, SFs had a substantial impact on reducing the crack widths at the peak load but there was no significant difference when 1% and 2% SFs were used (Figure 20). Alternatively, using 1% SFs did not have an extensive impact on reducing the crack widths when 100% RCA was used (Figure 20c), but using 2% SFs improved the crack widths in all specimens. According to Figure 20,using 2% SFs significantly reduced the crack widths at the peak load, in contrast to using 1% SFs. Conversely, increasing the RCA content reduced the ultimate crack width reduction effect of SFs. Figure 20: _Cont._