## 3 Discussion of Results
### Flexural Strength and Toughness of Pre-Cracked Beams in Marine Tidal Zone  
Figure 6 shows the load-vertical deflection diagrams for pre-cracked SFRC, RC, (R+S)C, and PC beams in the tidal zone at 28, 90 and 180 days. It was found that the \(P_{max(\text{PC})28}\) is approximately 6% higher than \(P_{max(\text{Pr-SFRC})28}\) in the tidal zone. However, the \(T_{(\text{Pr-SFRC})28}\) was 441% higher than \(T_{(\text{PC})28}\). It may be related to the more important role of steel fiber in \(T\) rather than the \(P_{max}\). By addition of steel fiber to pre-cracked RC beams, the \(P_{max(\text{Pr-RC})28}\) and \(T_{(\text{Pr-RC})28}\) were decreased 13% and 11%, respectively. It may be due to a higher porosity of concrete in pre-cracked (R+S)C beams rather than pre-cracked RC beams at 28 days. The effect of steel fiber on the decrease of \(P_{max(\text{Pr-RC})28}\) and \(T_{(\text{Pr-RC})28}\), was approximately the same. Moreover, by the addition of steel fiber to the pre-cracked RC beams, \(S.S_{(\text{Pr-RC})28}\) was decreased by about 11%. \(P_{max(\text{Pr-SFRC})90}\) was 8% lower than \(P_{max(\text{PC})90}\), \(T_{(\text{Pr-SFRC})90}\) was 482% higher than \(T_{(\text{PC})90}\). \(P_{max(\text{Pr-(R+S)C})90}\) and \(T_{(\text{Pr-(R+S)C})90}\), were about 17% higher than \(P_{max(\text{Pr-RC})90}\) and \(T_{(\text{Pr-RC})90}\). The \(S.S_{(\text{Pr-(R+S)C})90}\) is 16% more than \(S.S_{(\text{Pr-RC})90}\). At 180 days, it was cleared that the \(P_{max(\text{PC})180}\) is approximately 7% higher than \(P_{max(\text{Pr-SFRC})180}\) in the tidal environment. However, the \(T_{(\text{Pr-SFRC})180}\) was 387% higher than \(T_{(\text{PC})180}\). It may be due to the bolded role of steel fiber in \(T\) rather than \(P_{max}\). By addition of steel fiber to pre-cracked RC beams, \(P_{max(\text{Pr-RC})180}\) and \(T_{(\text{Pr-RC})180}\) were increased by about 43%. Reduction of steel bar corrosion in pre-cracked (R+S)C beams and an increase of \(P_{max(\text{Pr-R})C}\) and \(T_{(\text{Pr-RC})}\), \((\text{Pr-RC})\) may be due to three reasons: (1) the cracks width in (R+S)C beams is lower than the RC beams due to the bridging of cracks by the steel fibers and the higher fracture resistance of (R+S)C beams; (2) based on observation analysis, the formation of self-healing products in some of the cracks in the SFRC beam is considerable; and, (3) anodic and cathodic region are formed in steel bars when the corrosion of the steel bar will happen in pre-cracked RC beams. In the case of (R+S)C beams, steel fibers are distributed randomly. Consequently, it is possible to touch the steel bar and fiber and interconnect in the cover zone. Due to their connectivity, the anodic region is extended from the steel bar to steel fibers. Hence, the steel fibers play the role of the sacrificial anodic zone and the corrosion in the cathodic region continues until the availability of hydroxyl ions. Thus, steel fiber will be corroded before the steel bar and the corrosion of steel bar will be reduced or stopped. The rest of the steel fibers that is disconnected to the steel bar will be preserved by the concrete alkalinity [13]. Therefore, in pre-cracked (R+S)C beams, bonding between bar and cement past will be higher than the pre-cracked RC beams. Consequently, \(P_{max}\)(Pr-(R+S)C) and \(T_{(\text{Pr-(R+S)C})}\) will be higher than \(P_{max}\)(Pr-RC) and \(T_{(\text{Pr-RC})}\). It was indicated that by addition of steel fiber to the pre-cracked RC beams, \(S.S_{(\text{Pr-RC})|80}\) is increased by 42%. It may be because of the steel fiber role in the limitation of cracking and reducing the growth of cracks, as well as the decreasing of porosity in higher ages. At the beginning of the diagram, the slope of diagram for pre-cracked (R+S)C beams in tidal zone was higher than pre-cracked RC beam at 180 days. It indicated that the higher rigidity of pre-cracked (R+S)C beams rather than pre-cracked RC ones.