Interfacial modification: The dynamic compression properties and enhancement mechanism of concrete added with micro-nano hierarchical carbon-based fiber

The modification of interfacial characteristics between carbon fiber and matrix (F/M) is one of the most pressing issues in the research related to carbon fiber reinforced concrete (CFRC). Herein, carbon nanotubes were grafted onto the surface of carbon fiber using an ultrasonic-assisted electrophoretic deposition technique to create a carbon-based fiber with micro-nano hierarchical structure (CNTs-CF) for concrete modification. The impact test of concrete (CCMC) added with micro-nano hierarchical carbon-based fiber was carried out by using split Hopkinson pressure bar (SHPB), and the effects of CNTs-CF and strain rate on the dynamic compression mechanical properties of concrete specimens were investigated. The microstructures and interfacial characteristics of CNTs-CF and CCMC were characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results indicate that the CNTs-CF improves the internal F/M interface toughness due to its synergistic filling, bridging, and crack arresting effects, thus effectively relieving the local stress concentration and enhancing the dynamic compression properties of concrete. In the strain rate range of 50–120 s−1, as compared to CFRC, when the volume content of CNTs-CF is 0.3%, the dynamic compressive strength and peak strain of CCMC increase by 11.98% and 7.16%, respectively. When the volume content of CNTs-CF is 0.4%, the dynamic ultimate strain of CCMC increases by 5.52%.