Reinforcement Efficiency of Modified Carbon Nanofiber in High-Performance Concrete Nanocomposite

Graphite nanomaterials offer distinct features for effective reinforcement of cementitious matrices in the pre-crack and post-crack ranges of behavior. In the work reported herein, carbon nanofiber was chosen for use in high-performance concrete. Synergistic actions of carbon nanofibers and polyvinyl alcohol (PVA) fibers in high-performance concrete were also investigated. Carbon nanofiber surfaces were modified by introduction of hydrophilic groups in order to improve their dispersion and interfacial interactions in cementitious matrices. An experimental program was conducted in order to assess the contributions of modified carbon nanofiber to diverse engineering properties of high-performance concrete. A statistical optimization program was implemented in order to identify optimum dosage of nano-and micro-scale reinforcement systems in high-performance concrete. The experimental results verified that optimum reinforcement systems comprised both carbon nanofiber and (micro-scale) PVA fiber. The gains in concrete engineering properties realized with optimum (nano-and micro-scale) reinforcement could not be matched by those provided by nano-or micro-scale reinforcement used alone. This finding supports the hypothesis that nano-and micro-scale reinforcement play complementary/synergistic roles in concrete by providing reinforcing effects at different scales and are also due to the benefits rendered by nanomaterials towards interfacial stress transfer and pullout behavior of fibers.