Residual Flexural Strength of Concrete Reinforced with Recycled Carbon Fibers from Wind Turbine Blades

The study aims to assess the potential of recycled carbon fibers recovered from end-of-life wind turbine blades as a sustainable reinforcement material for concrete and to establish correlations between fiber parameters and the mechanical behavior of fiber-reinforced concrete. The research focuses on how fiber length, content, and cement type affect the residual flexural strength and cracking behavior of FRC. The experimental program included 48 concrete mix series with varying fibre lengths (25, 38, and 50 mm), dosages (0, 2, 4, and 8 kg/m³), cement types (CEM I 42.5 and CEM II 42.5R/A-V), and water-to-cement ratios (0.50 and 0.40). Mechanical properties such as compressive strength, tensile strength, modulus of elasticity, and residual flexural strength were evaluated. Notched beams underwent three-point bending tests, and the progression of cracks was tracked using the digital image correlation method. The analysis revealed that enhancing both the fiber content and length generally bolstered the toughness and post-cracking characteristics of concrete, with a notable effect observed for fibers ranging from 38 to 50 mm in length when used at a dosage of 8 kg/m³. However, the effects depend on the fiber recovery technology and the base concrete strength, which may influence the results and should be considered as a limitation of this study.