We investigate engineering applications of recycled nylon fibers obtained from waste fishing nets, focusing our attention on the use of recycled nylon fibers as tensile reinforcement of cementitious mortars. We begin by characterizing the tensile behavior of both unconditioned and alkali-cured recycled nylon fibers obtained through manual cutting of waste fishing net filaments, with the aim of assessing the resistance of such materials to chemical attacks. Next, we deal with compression and bending tests on cementitious mortars reinforced with recycled nylon fibers, and establish comparisons with the experimental behavior of the unreinforced material. In our analysis of different weight fractions and aspect ratios of the reinforcing fibers, we observe marked increases in the tensile strength and toughness of the nylon reinforced mortar, as compared with the unreinforced material. The presented results emphasize the high environmental and mechanical potential of recycled nylon fibers for the reinforcement of sustainable construction materials

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The winding of Fibre Reinforced Polymer (FRP) tows around longitudinal reinforcing bars provides a novel method for the fabrication of reinforcement cages for concrete structures. A key limitation on the contribution of FRP to the shear capacity of a concrete member is found at corners, where stress concentrations can lead to premature failure. An experimental programme, comprising 30 test samples, was undertaken to assess the bend capacity of filament wound FRP (W-FRP) shear links manufactured using a carbon tow impregnated with epoxy resin. A new methodology was developed to allow for rapid testing of the samples as well as their self-realignment during load application. A fixed bend radius of 5mm and six non-circular fibre cross sectional areas having different width-thickness ratios were considered. Additionally, 18 samples were tested to measure the tensile properties of the straight reinforcement. The results indicate that W-FRP exhibit improved bend strength as compared to conventional FRP with circular sections, as a larger width-thickness ratio of the reinforcement provided more strength for a given cross sectional area. A good correlation between the test results and predictions of the W-FRP bend strength was observed when the specimens were modelled as a collection of transformed individual circular sections.

This paper describes the outcomes of recent research that is, for the first time, aiming to completely replace internal steel reinforcement in concrete structures with knitted prefabricated cages made of highly durable fibre reinforced polymer (FRP) reinforcement. The proposed manufacturing technique, based on the filament winding process, allows the reinforcement to be fabricated in a precisely calculated geometry with the aim of providing tensile strength exactly where it is needed. The resulting Wound FRP (W-FRP) cage designs capitalise on the extraordinary flexibility and lightness offered by FRP construction materials. This paper presents fundamental analytical and experimental studies that demonstrate the effectiveness of the wound reinforcement system and forms the basis of future efforts to develop fully automated manufacturing methods for concrete structures.