## 4 Discussion  
In this study, a literature review was conducted on the impact of fibres on durability and, given their intrinsic connection, the deterioration of the load-bearing capacity of rebar in RR-FRC elements. In this regard, many of the still unresolved issues related to the degradation of RC elements are found to be present in the case of RR-FRC elements but with added complexity originating from the presence of fibres. Quantifying the effects of fibres through direct comparison of experimental findings was found to be challenging due to the substantial variations in key parameters influencing chloride ingress (e.g., concrete cover, water-to-binder ratio, exposure duration, concentration of chlorides in the solution) and the effects of fibres on mechanical performance (e.g., crack widths, fibre quantity, fibre material type) across different experimental campaigns. This is further complicated by the different loading conditions. Namely, cracks produced via pure axial tension exhibit distinct characteristics compared to those originating  
Figure 11: Structural performance of elements investigated in [85]. from flexural loading. Axial tension cracks propagate uniformly through the entire cross-section RC, forming parallel edges due to the even stress distribution. In contrast, flexural cracks develop a V-shaped geometry as they initiate at the tension face and taper towards the neutral axis, which limits their propagation depth. In this context, the results from campaigns employing flexural loads as a pre-cracking method or sustained loads are more representative of most structures, as pure axial tension is seldom observed in RC elements. Nevertheless, findings from campaigns utilising pure axial tension remain valuable for advancing knowledge in this field, as the stress field in pure axial tension, locally, near the rebar in tension, may resemble that of flexural loading. It is important to note that several of the reviewed studies used some of the techniques to accelerate corrosion. Namely, chloride-induced rebar corrosion is inherently slow, and it often takes years for its effects to manifest themselves, which makes accelerated methods appealing for obtaining results within a shorter timeframe. In this regard, the use of wetting and drying cycles is more representative of natural corrosion, as it allows for progressively increasing the concentration of chlorides in the solution after each cycle; however, the downside is that it is slower than the use of direct current (DC) to facilitate corrosion. DC methods can vary depending on whether the potential (\(U\)) or current (\(I\)) is applied to the element, with each offering distinct advantages and drawbacks (i.e., fixed \(U\) is easier to apply and allows for the variation in \(I\) with changes in the resistance (\(R\)), which is more representative of natural corrosion, whereas fixed \(I\) allows for precise corrosion level to be achieved, thus allowing for the reduction in variables in the experimental program). However, if the applied voltage is higher than 1.3 V, water electrolysis occurs [93], leading to the formation of oxygen and hydrogen gases, which have been shown to cause damage at the steel-concrete interface [94], which itself is recognised as one of the important parameters regarding chloride-induced corrosion [95]. In the case of controlling accelerated corrosion by the value of the current, the resulting corrosion current density often results in values that are significantly higher (>10.00 \(\mu\)A/cm\({}^{2}\)) [96] than the values typically observed in tests with natural corrosion (from 0.10 \(\mu\)A/cm\({}^{2}\) to 10.00 \(\mu\)A/cm\({}^{2}\)) [97; 98]. Furthermore, in the case of DC-accelerated corrosion, the whole bar usually acts as an anode, whereas in natural corrosion (or in wetting/drying cycles), parts of the rebar act both as anodes and cathodes.