2025-06-112025-06-112025-04-21Ruiz Martínez, J.D., Ríos Jiménez, J.D., Cifuentes-Bulté, H. y Leiva Fernández, C. (2025). Multi-scale toughening of UHPC: synergistic effects of carbon microfibers and nanotubes. Fibers, 13 (4), 49. https://doi.org/10.3390/fib13040049.2079-6439https://hdl.handle.net/11441/174222This study investigates multi-scale reinforcement of Ultra-High-Performance Concrete through targeted modifications of its mechanical and fracture-resistant properties via carbon microfibers and carbon nanotubes. The research employed comprehensive characterization techniques including workability tests, mercury porosimetry for microscale porosity analysis, and X-ray tomography for macro-scale pore evaluation. Mechanical performance was assessed through compression strength, tensile strength, and fracture energy measurements. Results demonstrated significant performance enhancements testing UHPC samples with 6 mm carbon microfibers (9 kg/m3) and varying carbon nanotubes dosages (0.11–0.54 wt%). The addition of carbon microfibres improved compressive strength by 12%, while incorporating 0.54 wt% carbon nanotubes further increased strength by 24%. Remarkably, the combined reinforcement strategy yielded a 313% increase in tensile strength compared to the reference mixture. The synergistic effect of carbon fibers and carbon nanotubes proved particularly effective in enhancing concrete performance. This multi-scale reinforcement approach presents a promising alternative to traditional steel fiber reinforcement, offering superior mechanical properties and potential advantages in corrosive environments.application/pdf20 p.engAttribution 4.0 Internationalhttp://creativecommons.org/licenses/by/4.0/Ultra-high-performance fiber-reinforced concreteThermogravimetric analysisCarbon microfiberCarbon nanotubesFiber–matrix interactioninfo:eu-repo/semantics/articleinfo:eu-repo/semantics/openAccesshttps://doi.org/10.3390/fib13040049