Long-term mechanical performance of concrete with high amounts of wind turbine blade mixed waste: Analysis of temporal evolution mechanisms

Fiber-Reinforced Concrete (FRC) was manufactured by the addition of high percentages of mechanically recycled wind-turbine blades, known as Raw-Crushed Wind-Turbine Blade (RCWTB). This sustainable material was added as aggregate replacement up to 10 % vol., while keeping the cement content equal for all mixes, and the effects on several fields were evaluated. First, strength (compressive, tensile splitting and flexural testing) and stiffness were evaluated at 7, 28, 90 and 180 days of age. Results showed that low RCWTB contents improved compressive (above 60 MPa) and tensile strengths (over 6.50 MPa under bending) due to enhanced matrix compactness. Nevertheless, the large proportions of deformable particles when using high RCWTB contents slightly hindered mechanical performance. Second, temporal strength development mechanism was evaluated through Scanning Electron Microscopy (SEM) on specimens that underwent mechanical testing and explained through schematics by the authors. This analysis revealed that the porous particles of RCWTB, acting as water reservoirs, accelerated matrix hydration and improved Interfacial Transition Zones (ITZ) around the Glass Fiber-Reinforced Polymer (GFRP) fibers of RCWTB, globally enhancing early-age strength. Third, low RCWTB levels improved abrasion resistance (up to 14.73 %), while high contents reduced surface quality but maintained acceptable performance. Finally, thermal conductivity remained stable following RCWTB incorporation at low levels and increased at higher contents (up to 35.75 %) but remained within typical FRC ranges. Therefore, this research ensures proper early-age and long-term overall performance of FRC produced with RCWTB, enhancing sustainability while yielding an improved concrete material suitable for a wide variety of applications.

This research work was supported by the Spanish Ministry of Science, Innovation and Universities MICIU, AEI, EU, ERDF and NextGenerationEU/PRTR [grant numbers PID2023-146642OB-I00; 10.13039/501100011033; TED2021-129715B-I00; FPU21/ 04364]; the Junta de Castilla y León (Regional Government) and ERDF [grant number UIC-231; BU033P23; BU066-22]; and, finally, the University of Burgos [grant number SUCONS, Y135.GI].