The concrete industry has long been adding discrete fibers to cementitious materials to compensate for their (relatively) low tensile strengths and control possible cracks. Extensive past studies have identified effective strategies to mix and utilize the discrete fibers, but as the fiber material properties advance, so do the properties of the cementitious composites made with them. Thus, it is critical to have a state-of-the-art understanding of not only the effects of individual fiber types on various properties of concrete, but also how those properties are influenced by changing the fiber type. For this purpose, the current study provides a detailed review of the relevant literature pertaining to different fiber types considered for fiber-reinforced concrete (FRC) applications with a focus on their capabilities, limitations, common uses, and most recent advances. To achieve this goal, the main fiber properties that are influential on the characteristics of cementitious composites in the fresh and hardened states are first investigated. The study is then extended to the stability of the identified fibers in alkaline environments and how they bond with cementitious matrices. The effects of fiber type on the workability, pre- and post-peak mechanical properties, shrinkage, and extreme temperature resistance of the FRC are explored as well. In offering holistic comparisons, the outcome of this study provides a comprehensive guide to properly choose and utilize the benefits of fibers in concrete, facilitating an informed design of various FRC products.

Fiber-reinforced concrete (FRC) is a promising construction material mainly because of the crack-controlling mechanisms that discrete fibers can impart to inherently brittle concrete. Macrofibers, in particular, have been proven effective for providing post-crack ductility and toughness, while synthetic fibers are a promising solution to avoid corrosion-related durability issues. To assess the performance enhancement provided by macro-synthetic concrete fibers, this study performs flexural tests on FRC beams containing three different types of macro-synthetic fibers. The selected fibers include polypropylene (PP), polyvinyl alcohol (PVA), and alkali-resistant glass (ARG) macrofibers mixed at volume fractions of 0.5%, 1.0%, and 1.5%. Static and dynamic fresh properties are monitored using the vibrating Kelly ball (VKelly) test. Beam specimens are then placed under a third point bending configuration, as per ASTM C1609 Standard, to measure load versus mid-span deflection. Strength and toughness parameters are derived from the load–deflection data to assess the flexural performance of the FRC composite systems under consideration. The parameters of interest include first peak strength (pre-crack flexural strength) and post-crack residual strength and toughness provided by fiber addition. Of the mixtures tested, ARG fiber mixtures show the highest residual strength and toughness values, followed by PP and PVA fiber mixtures. ARG fibers produce the most workable mixtures at all fiber volumes, while PVA fibers show a tendency to encounter dispersion issues at higher volume doses. The outcome of this study is expected to facilitate the selection of fibers by giving insight into their relative contribution to fresh and hardened flexural properties of FRC.

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