Abstract: The surface of carbon fiber is smooth and it is inert, which results in poor compatibility with cement-based material. The surface properties of carbon fiber can be improved by electroless nickel plating. The surface elements and tensile strength of nickel-plated carbon fiber were characterized, and the nickel-plated carbon fiber modified cement-based material were prepared. Meanwhile, the mechanical properties, crack resistance, impermeability and frost resistance of nickel-plated carbon fiber modified cement-based materials were studied and compared with carbon fiber modified cement-based materials. The interfacial modification mechanism of nickel-plated carbon fiber/cement based material was analyzed by SEM. The results show that, compared with carbon fiber, nickel-plated carbon fiber exhibits higher surface oxygen content and greater tensile strength; it provides better improvement in the mechanical properties and durability of cement-based materials as well as superior dispersion in the matix, with an optimal content of 0.9%. With this fiber content, the flexural strength and compressive strength of the cement-based materials increase by 32.88% and 26.61%, respectively, while the total cracking weight, water seepage height, mass loss rate, flexural strength loss rate, and compressive strength loss rate decrease by 34.76%, 53.19%, 57.41%, 51.29%, and 45.42%, respectively. Numerous pores are observed at the interface of carbon fiber/cement-based material, but the interface of nickel-plated carbon fiber/cement-based material is well bonded. The oxygen element on the surface of nickel-plated carbon fiber improves its hydrophilicity, and the nickel coating enhances its mechanical interlocking force with cement-based material.

Key words: cement-based materials, nickel-plated carbon fiber, mechanical properties, crack resistance and impermeability, frost resistance