Deformation Performance and Fracture Toughness of Carbon-Nanofiber-Modified Cement-Based Materials

this study, carbon nanofibers (CNFs) were uniformly dispersed into cement-based materials by the ultrasonic dispersion method to prepare cement-based materials modified by CNFs, and the deformation performance and fracture toughness of the CNF-modified cement-based materials were studied. The results showed that CNFs could inhibit the autogenous shrinkage and drying shrinkage of cement paste, and significantly delay the cracking time of cement mortar. When the dosage of CNFs was 0.05 wt%, the cracking time of cement mortar was extended by nearly 1.5 times longer than that of the control group. The fracture performance of the CNF-modified cement mortar was studied by the fracture test of a three-point bending beam, and the fracture toughness of the mortar was evaluated by double-K fracture parameters. The results showed that at 0.05 wt% dosage of CNFs, the unstable fracture toughness and fracture energy of the mortar increased by 53.5% and 17.2%, respectively. Scanning electron microscopy images illustrated that CNFs could produce bridging and pullout effects in the cement-based materials and retard crack propagation, thus reducing shrinkage deformation and improving fracture toughness.