▎ 摘　　要

Mechanical behavior of carbon fiber (CF) reinforced cement-based materials greatly depends on the dispersion of CF and interfacial properties between the CF and cement matrix. In this study, graphene oxide (GO) was utilized to modify the surface properties of CF, including the roughness, wettability and chemical reactivity, and the graphene oxide/carbon fiber (GO/CF) hybrid fibers were fabricated by a newly designed electrophoretic depositing method. The scanning electron microscopy and contact angle measurement results indicated that GO/CF hybrid fibers not only had a rougher surface which was expected to improve the physical friction when CF was pulled out from cement matrix, but also had a higher wettability surface that made it easier to contact with cement hydrates as nucleation sites. In addition, GO/CF hybrid fibers were capable of high chemical reactivity due to the introduction of GO with many functional groups, which ensured them more likely to interact with cement hydrates due to the hydrogen bonding at interface and therefore benefited to strengthen the bonding between the CF and cement matrix. In terms of mechanical behavior, three-point bending test showed that compared with the CF reinforced cement paste, flexural strength of the GO/CF hybrid fibers reinforced cement paste was enhanced by 14.58%, and could be further improved by 10.53% when the GO/CF hybrid fibers were pre-dispersed in the GO solution and then mixed with cement powders. The larger electrostatic repulsion and steric stabilization led to the better dispersion of GO/CF hybrid fibers in GO solution, which were responsible for the further mechanical enhancement of cement paste. In conclusion, the research outcomes provided a novel way for utilizing GO as both of dispersant and surface modifier to improve the dispersion of CF in cement and strengthen its bonding with cement hydrates, consequently achieving a significant enhancement in the mechanical properties of cement paste. (C) 2018 Elsevier Ltd. All rights reserved.