Nano silica grafted on modified polyacrylonitrile fiber improves the interfacial strength of fiber‐reinforced concrete

Cement is known to be brittle and usually reinforced with fibers. However, there is a lack of effective chemical bonding between organic fibers and inorganic cement, resulting in a weaker interfacial bonding strength. In this paper, amino hyperbranched polymer (HBP) was used to modify the surface of polyacrylonitrile (PAN) fibers, and then silica nanoparticles (SiO 2 NPs) were grafted on the surface of modified PAN fibers to realize the inorganic treatment of organic fibers. The modified PAN fibers applied to cement concrete can significantly enhance the interfacial strength between the fibers and cement. The morphology and chemical composition of the modified PAN fibers were characterized by scanning electron microscope, atomic force microscope, electron energy dispersive spectroscopy, and Fourier transform infrared spectroscopy, and the influence of grafting conditions on grafting effect was analyzed. The results show that SiO 2 NPs were evenly distributed on the surface of PAN fiber. When SiO 2 NPs concentration was 4%, grafting temperature was 50°C, and grafting time was 4 h, the grafting degree of SiO 2 NPs grafted PAN fiber can reach to 1.4%. After coating with SiO 2 NPs, the pullout bonding strength of the PAN fiber was increased from 5.5 to 6.5 cN.