Surface Hydrophilic Modification of Polypropylene Fibers and Their Application in Fiber-Reinforced Cement-Based Materials

Among the various polymer fibers available, polypropylene (PP) fibers are often used to improve the impermeability, impact resistance, anti-wear and crack resistance of concrete. In order to improve the interfacial adhesion between PP fibers and cement a series of PP composite fibers were prepared by melt spinning with micro-silica (MSi) as a hydrophilic modifier and the structure and properties of the composite fibers were studied. The results showed that the composite fibers displayed rougher and more hydrophilic surfaces than the pure PP fibers. As revealed by single fiber pull-out tests, the interfacial adhesive strength between the PP fibers and a cement matrix increased obviously after adding the MSi to the PP fibers. The flexural strength and compressive strength of the cement mortar blended with the composite fibers were much better than those of the cement modified by pure PP fibers. The cement mortar enhanced by the composite fibers containing 10 wt.% of MSi showed the best mechanical strength, which we suggest was caused by a balance between fiber strength and interfacial adhesive strength. In general, our research indicated that the mechanical properties of PP fiber reinforced cement-based materials could be further enhanced by mixing appropriate amounts of MSi in the PP fibers which provides a novel strategy to design high-ρperformance materials for modern architecture.