## 1 Introduction  
The corrosion of rebars accelerates when cracking occurs in reinforced concrete (RC) members. Cracking in RC is a phenomenon that cannot be avoided under tensile or flexural loading. Many types of research have been performed on the width of cracks in RC members [1; 2; 3; 4; 5; 6; 7; 8; 9]. Cracking occurs because of exceeding the concrete tension strain from the maximum tension capability. Therefore, rebars endure the tension force beyond what caused the cracks [10; 11; 12; 13; 14]. In many theories, slip is ignored at the first stage of cracking [11; 12; 13; 14]. Therefore, the sections do not remain in place in the crack section. [PERSON] and [PERSON] [15] studied the flexural performance of a concrete beam made with 100% recycled coarse aggregate (RCA) that was subjected to fatigue failure. The results were compared with those of natural coarse aggregate (NCA) concrete beams. They revealed that using 100% RCA in concrete in the place of NCA resulted in poor fatigue performance. [PERSON] and [PERSON] [16] studied the long-term deflection and flexural performance of reinforced concrete beams with RCA. The specimens were loaded for 360 days. Furthermore, the experiments were compared with ACI 318 analytical outcomes and a new model was proposed to calculate the long-term flexural deflections. Similar crack patterns were observed, regardless of the aggregate type, even though several cracks occurred in the beams made with recycled aggregate. [PERSON] [17] studied the flexural behaviour of reinforced concrete beams made with recycled waste materials. In this study, polyethylene terephthalalate (PET) wastes were used as a recycled material. The results indicated that PET waste could be used in concrete in proportions up to 15%. [PERSON] and [PERSON] [18] investigated the flexural behaviour of steel fibres (SF) RCA concrete. The flexural strength, toughness and deflection dramatically improved by increasing the SF content. Based on previous studies, it is clear that adding SFs to RCA concrete beams is an effective method for improving their performance. [PERSON] et al. [19] evaluated the influence of RCA on the flexural performance of reinforced concrete beams. The specimens were subjected to four-point loading after 28 days. The cracking behaviour showed differences between RCA and conventional concrete. Therefore, it is possible that using SFs could enhance the bending performance of RCA beams. [PERSON] et al. [20] compared the flexural performance of RCA-reinforced concrete with the Eurocode equations, based on 217 experimental specimens. They found that Eurocode 2 could anticipate the bending and shear resistance of RCA concrete beams without stirrups. [PERSON] et al. [21] used brick as the RCA to manufacture specimens. The results were compared with the proposed ACI 318-14 model to predict the flexural performance of the concrete beams. In comparison with virgin brick aggregate, the use of RCA did not reduce the cracking moment nor the maximum load-bearing capacity of the specimens. [PERSON] et al. [22] used RCA at 0%, 20%, 40%, 60%, 80% and 100% by weight to produce concrete. Although the RCA beams were weaker than the NCA beams, improvements in the strength and abrasion resistance were obtained because of better bonding between the RCA and the cement paste due to the increased surface porosity and roughness of RCA. Conversely, SFs offer a solution for reducing crack propagation. In some studies, the shear cracking in RC beams was investigated by using SFs only, a shear rebars ratio and the combination of stirrups and SFs [23; 24; 25; 26]. Furthermore, the post-cracking stress transferability in concrete increases by increasing the SF content [27; 28; 29; 30; 31; 32]. To evaluate the correct potential of the fibres, the transferred post-cracking stress through cracks must be considered by including an additional contributing term [33]. The slip occurred in tension rebars. Therefore, the load-displacement relationship can be measured as a criterion to study cracking [34; 35; 36; 37; 38; 39; 40].