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The study of damage processes in concrete and their effects on the residual properties represents a key point related to the service life of reinforced concrete (RC) structures. The use of steel fibers in RC beams mainly improves the cracking control and the shear bearing capacity. Considering the shear behavior, the presence of fibers not only leads to partial or total substitution of secondary reinforcement, but they can also result in a modification of the failure behavior from a shear failure (brittle) to a bending (ductile) one. The contribution of fibers on flexural and shear behavior of sound and damaged RC beams was investigated using alkali‐silica reaction as a damaging tool. First, the evolution of deformations and cracks were measured on creep tests of RC beams with and without fibers and reactive aggregates. Second, the flexural and shear behavior of damaged and undamaged beams incorporating steel fibers were compared. Results showed that alkali‐silica reaction damage can provoke a reduction of RC beam ductility, while the flexural strength is preserved. Regarding shear, it was observed that even in damaged concrete, fibers were able to control the crack propagation and increase the bearing capacity. [ABSTRACT FROM AUTHOR]

The use of fibers in Reinforced Concrete (RC) elements changes their cracking pattern, leading to narrower and more closely spaced cracks. In addition, the presence of fibers can improve the steel‐to‐concrete bond behavior reducing the steel‐to‐concrete interface damage after cracking. Cracks and steel‐to‐concrete interface damage work like paths, for aggressive agents, to reach the rebar in cracking elements, reducing the initiation period of the corrosion process, and favoring the corrosion at the intersection between cracks and reinforcement. In this context, this article discusses an experimental program on tension ties mechanically cracked and exposed to a chloride‐rich environment with the purpose to check and eventually adequate the typical electrochemical measurements, used in the case of RC elements, for Steel Fiber Reinforced Concrete (SFRC). Adjustments related to degradation morphology and interference of steel fibers are proposed and used on Fiber Reinforced Concrete (FRC) elements for monitoring the influence of cracks and fibers on corrosion propagation. Finally, these proposed modifications were checked and validated against the results obtained by monitoring SFRC beams in the cracked stage. [ABSTRACT FROM AUTHOR]

The use of fibers in reinforced concrete (RC) beams mainly improves both the bearing capacity and the cracking control. In this way, positive effects on the service life of RC structures can be expected. In this paper, the fiber influence on the flexural behavior of RC beams with different longitudinal reinforcement ratios (0.5% ≤ ρs ≤ 1.2%) is analyzed by testing small‐scale RC beams. Concretes incorporating 0, 25 and 50 kg/m3 of steel, 6 and 12 kg/m3 of glass macrofibers, and 5 and 10 kg/m3 of polymer macrofibers were studied. Crack and deflection control, as well as bearing capacity and crack localization were evaluated for a broad range of fiber‐reinforced concrete (FRC) toughness. It is verified that fibers, in the longitudinal reinforcement ratio considered, improve the bending behavior at serviceability limit state (SLS) and ultimate limit state (ULS) of RC beams, without limiting the structure ductility. It was also confirmed the philosophy of the fib Model Code 2010, such that FRC can be considered as a composite material where performance parameters govern its mechanical behavior. Finally, the several data available allowed to deeply analyze fib Model Code 2010 formulations (mean crack spacing and flexural bearing capacity) and to propose modifications where needed. [ABSTRACT FROM AUTHOR]

It is well-known that the shear strength of reinforced concrete elements without web reinforcement is affected by different factors. Among them, tensile strength of concrete, longitudinal reinforcement ratio, shear span-depth ratio, size effect, axial force, and maximum aggregate size seem to be the most important. Concerning other parameters—for example, the width-to-effective depth ratio (b/d) —there is still disagreement within the research community about its possible influence on shear bearing capacity. In this context, the present research evaluates the influence of both the b/d and bar spacing-to-effective depth ratio (s/d) on the shear strength by means of an experimental program on 17 full-scale specimens characterized by b/d ranging from 0.5 to 3.5 and an s/d from 0.24 to 0.71. Results showed that, for b/d > 1, an increase in the b/d determines a non-negligible increment in the shear strength, whereas the s/d (in the considered range) does not affect the shear bearing capacity. [ABSTRACT FROM AUTHOR]

Authors' closure on the discussion of the article: "Assessing the influence of fibers on the flexural behavior of reinforced concrete beams with different longitudinal reinforcement ratios" (discussion by Marki'c et al.) The authors would like to thank the discussers for their interest and for opening a discussion on the ductility of RC elements with fibers, which is a very important topic. This possible negative influence is related to both longitudinal reinforcement (type and ratio) and the weighted ratio between the post-cracking performances of fiber reinforced concrete (FRC) and reinforcement strength properties. [Extracted from the article]

• A morphological and mechanical characterization of corroded rebars. • A chloride content analysis in cracked specimens exposed to chloride-rich environment. • Perpendicular to crack wall, positive influence of fibres on the reduction of chloride content. In Reinforced Concrete (RC) structures exposed to chloride-rich environments, reinforcement corrosion might be already initiated (especially at crack location). A deep knowledge on the correlation between the mechanical properties of corroded bars and corrosive attack morphology, useful for the evaluation of the residual bearing capacity of structure, is still lacking. In this paper, morphological and mechanical characterization of steel reinforcement embedded in RC specimens (with and without fibers) both in cracked stage and subjected to cyclic exposure to a 5 % NaCl solution for 280 days was carried out. Although a chloride content higher than the critical chloride threshold was also measured in correspondence of uncracked concrete, corrosive attacks were observed only in correspondence of cracks. Pits were mostly characterized by a shallow morphology, which led to a rebar diameter loss ranging between 1 and 10 %. Furthermore, the results showed that both yielding and ultimate load of corroded rebars can be predicted by combining circular residual cross-section and mechanical properties of uncorroded rebars. [ABSTRACT FROM AUTHOR]