Utilization of recycled synthetic fibers in concrete with a focus on structural properties enhancement: a critical literature review

Research involving the application of waste materials in concrete has gained prominence in the academic community, aiming to promote cleaner waste management while enhancing concrete properties. This study reviews publications that have assessed the influence of recycled synthetic fibers on concrete, observing improvements in their main properties. The analysis of results reported in the articles revealed that, for any type of fiber, there is a significant loss in workability that worsens as the fiber dosage increases. Additionally, improvements in compressive, flexural, and tensile strengths are observed up to a dosage of 2% of the fiber volume added to the concrete. This can be attributed to the "bridging" effect caused by the adhesion and friction of the fibers to the concrete matrix, delaying the initiation and propagation of cracks and microcracks under mechanical stress or drying shrinkage. It was also reported that the modulus of elasticity was not significantly affected. Furthermore recycled fibers demonstrated performance compatible with commercially available virgin fibers, indicating that they can serve as effective replacements, witch contributes to the mitigation of natural resource extraction, energy consumption, and CO2 generation from the production of virgin fibers, as well as promoting the circular economy.