61 / 2022-03-31 15:44:27

Improved interfacial strength of carbon fiber in cement matrix by electrophoretic deposition

Carbon fiber, Cement-based composites, Electrophoretic modification, Nano-silica, Interfacial strength

Due to the excellent mechanical properties and high durability of carbon fibers (CFs), they have been extensively applied in CF-reinforced cementitious composites. However, one of the main restrains of this composites are the poor interfacial strength between the intrinsic hydrophobic CFs and cementitious, which makes the high tensile strength of CF cannot be effectively utilized. In this present work, the surface of CFs was modified by electrophoretic deposition of nano-silica (NS) to improve the interfacial strength. The effects of different parameters such as voltage range, deposition time, electrolyte concentration calcium salt concentration and NS mass fraction on the deposition results were studied. The microstructures and the surface roughness of the modified CFs were analyzed by scanning electron microscope (SEM) and atomic force microscope (AFM), respectively. The surface functional groups and elements distribution of the modified CFs were characterized by X-ray photoelectron spectroscopy (XPS). The CFs single bundle pull-out test and the micro characterization of the interface between cement and CFs were also carried out. The effects of modified CFs on the interface properties between cement under different parameters were studied by orthogonal analysis. The results indicated that the NS was successfully deposited on the surface of CFs, which also leaded to the increase of fiber surface roughness compared with untreated fibers. Orthogonal analysis showed that the deposition voltage was the most important factor. The single bundle pull-out test represented a significantly enhanced interfacial strength between the cementitious matrix and CFs at higher NS concentration and the pullout strength was enhanced by as much as 139%，which can be attribute to the deposition of NS on the surface of CFs not only increasing the surface roughness thus to enhancing the physical anchoring effect, but also enhancing the chemical bonding between the fiber and the matrix by the silica pozzolanic reaction.