Fiber addition is a common strategy to enhance concrete's durability, avoiding cracks and reducing penetration of harmful agents. In this research, a sustainable fiber-like material obtained from mechanical recycling of dismantled wind-turbine blades and made up of glass fiber-reinforced polymer (GFRP) fibers and microfibers, balsa wood, and polymeric particles, named raw-crushed wind-turbine blade (RCWTB), was added into concrete in high quantities. For studying dimensional stability and water transport behavior of concrete containing this waste, 11 mixes were manufactured with RCWTB contents up to 10 vol.% as aggregate replacement. Dimensional stability was enhanced by RCWTB incorporation, as shrinkage and linear coefficient of thermal expansion were reduced up to 47% and 17%, respectively. Furthermore, when tested for accelerated aging, RCWTB mixes experienced similar or slightly lower thermal strains compared to the reference mix. RCWTB also reduced the variations in the mechanical properties after accelerated aging and even led to improved flexural (+9.75%) and compressive (+11.14%) strengths, partly thanks to the proper stitching of the matrix by the GFRP fibers, as scanning electron microscope images and energy dispersive x-ray spectra demonstrated. Concrete porosity in both full-immersion and capillarity terms increased up to 70%–75% following RCWTB addition due to higher air entrainment and the porous particles of balsa wood in RCWTB acting as water-storage points, yet porosity was always within structural standards. Overall, mixes with proven proper performance regarding both concrete dimensions were produced with high proportions of RCWTB, being therefore suitable for applications in which such performance is of utmost relevance.
