Valorization of macro fibers recycled from decommissioned turbine blades as discrete reinforcement in concrete

The extensive use of glass fiber-reinforced polymer (GFRP) composites has inevitably resulted in a large amount of FRP waste, posing a significant environmental threat. A recent study performed by the authors’ group of the present study pioneered a new mechanical method of recycling GFRP wind turbine blades into macro fibers, in which the macro fibers characterized by a fixed-length have been produced using a manual process of low efficiency and high cost, making it impossible for use in a practical application. In the present study, a shredding machine has been therefore used to efficiently process waste GFRP wind turbine blades into macro fibers of hybrid lengths lesser than 100 mm for being incorporated into concrete. A series of tests were carried out to investigate the properties of the resulting concrete, and the test results of beam specimens were then analyzed using a twice inverse analysis approach. The results of compression tests and four-point bending tests showed that the incorporation of recycled macro fibers led to a slump loss of 54%, a compressive strength reduction of 14.07%, a flexural strength improvement of 37.85% and a significant flexural toughness enhancement of 36.8 times at a fiber volume ratio of 2.5%, as compared to those of plain concrete. The direct-tensile strength and the corresponding tensile strain obtained by a twice inverse analysis approach were about 2.26 MPa and 134 με, respectively, as predicted by the inverse analysis based on flexural load-deflection curves. The macro fibers processed using a shredding machine are feasible for enhancing the performance of the resulting concrete, and can be economic-efficiently used for industrial scale applications.