## 5 Flexural Capacity and the Load-Displacement Relationship  
After evaluating the influence of SFs and RCA on the compressive and tensile behaviour of unreinforced concrete, 27 SF-reinforced RCARC beams were produced and measured, where the results are presented in this section. SFs were used at 0%, 1% and 2% (by volume). RCA was incorporated at 0%, 50% and 100% by weight. Furthermore, the effect of shear rebars was considered via different stirrup spacings. The load-displacement behaviour at the mid-span of the specimens, the maximum load-bearing capability and the crack widths and propagation were studied. In Figures 14-19, the loading capacity and load-displacement behaviour of the specimens are represented. Figure 16: Bending behaviour of specimens with various SF and RA contents and 200 mm shear rebars’ spacing. 20 TD: transverse reinforcement spacing 200 mm. Figure 15: Failure and crack propagation of the specimens without a stirrup. Figure 17: Failure and crack propagation in specimens with a 200 mm shear rebar spacing. Figure 18: Bending behaviour of specimens with various \(S\) values and RCA contents and a 100 mm shear rebar spacing. As per Figures 14 and 15, the maximum bearing capability was substantially increased by increasing the SF content due to the effective role of SFs in improving the compressive and tensile strength of the unreinforced concrete. Furthermore, using RCA had a momentous impact on the maximum loading capacity. Furthermore, SFs enhanced the bending resistance strength of concrete due to the lack/insufficiency of shear rebars. Hence, SFs played a role as partial transverse reinforcement and improved the shear performance of the concrete beams. Therefore, the SFs reduced the inclined and shear crack widths and led to improving the first crack loading. As seen in Figure 15, the lack of shear rebars led to shear failure of the specimens but crack propagation increased and the inclined crack widths were reduced by using RCA. Based on the models proposed by several standards, improving the compressive strength of the concrete led to improving the shear behaviour of RC beams. Therefore, according to the results of the compressive behaviour of the unreinforced concrete and the tested beams, RCA was used to produce RC beams without shear reinforcement when 2% SFs were used (Figures 14 and 15). According to Figures 16 and 17, the flexural behaviour improved by providing shear rebars spaced 200 mm apart, which was further enhanced by increasing the RCA content. Conversely, the maximum bearing resistance capacity dropped after the maximum bearing capability point when 100% RCA was used. This led to a dramatically increased crack propagation but the flexural capacity abruptly decreased after the maximum loading point in specimens without RCA. Furthermore, the flexural  
Figure 19: Failure in specimens with 100 mm stirrup spacing and crack propagation. capacity was increased by utilising SF. Furthermore, reducing the shear rebars' spacing was necessary. Therefore, enough stirrups should be provided and SFs should be added to the concrete mix. Conversely, reducing the shear rebars' spacing to 100 mm led to an increase in the bending capability and failure cracks occurred at the middle of the specimen's width with the maximum spacing (Figures 18 and 19). Adding SFs to concrete improved the bending performance of the specimens as a result of improving the compressive and stress-strain behaviour of the unreinforced concrete. The minimum shear rebars' spacing should be provided but SFs should be included as well. As it is seen in Figures 18 and 19, NCA could be replaced with RCA at 100% if enough stirrups and SFs are provided in the specimen by comparison with the control specimen (without RCA and SF). According to Figure 19, in addition to increasing the bond between the reinforcement and the concrete, cracks developed less when SFs were used due to the bridging role of the SFs. Therefore, specimens with 2% SFs showed greater ductility and did not fail suddenly.