Experimental Study On Mechanical Properties And Durability Of Fiber Reinforced Concrete

This paper is one part of the research on "the cracking resistance and application of fiber reinforced concrete used on wharf surface", which is the research project of Rizhao port office. The theoretical analysis and experimental research methods were used in this paper. Combined the existed research achievements of fiber reinforced concrete, different fiber reinforced concrete was experimentally investigated by adding flexible fiber and rigid fiber respectively into C20, C30and C40plain concrete. The flexible fiber is American Durafiber (The Durafiber is a kind of strands of polypropylene monofilament which is modified.) and domestic nylon fiber. The rigid fiber is domestic steel fiber. First the workability of fiber reinforced concrete was tested. Then the mechanical properties, impermeability and frost resistance property was tested after curing on standard condition for28days. Based on the theoretical analysis and combined the experimental results, the effect of the strengthening and toughening of fiber was analyzed. Two kinds of energy dissipation process and energy consumption model were proposed. The basic mechanical properties, flexural impact resistance, flexural fatigue resistance, impermeability, frost resistance and toughening mechanism of steel fiber reinforced concrete, Durafiber reinforced concrete, nylon fiber reinforced concrete and plain concrete were compared.The results show that the performance of fiber reinforced concrete as a whole is better than that of plain concrete. The fiber can improve the basic mechanical properties, flexural impact resistance and fatigue performance of concrete. Especially the effect of rigid fibers is better. The fiber can optimize the microstructure of concrete and improve the impermeability, frost resistance and durability of concrete. The effect of flexible fibers can improve the durability of concrete obviously.In order to deepen the experimental results and facilitate the further promotion and application of fiber reinforced concrete, the strengthening and toughening effect of the fiber reinforced concrete from the perspective of the internal mechanism were made clear with the phenomena and results of experiments. The energy was consumed much more in fiber reinforced concrete than in plain concrete. The energy was dissipated by matrix cracking in plain concrete, while the energy was dissipated by pull-out work and fracture work of fiber in fiber reinforced concrete. The process of fiber pull-out consumed more energy than the fiber fracture. Two energy dissipation models for flexible fibers and rigid fibers were built. The energy dissipation in the fracture process of flexible fiber reinforced concrete depended not only on the interface but also the physical properties of the fiber itself to a greater extent. The energy consumption in the process of rigid fiber pull-out from the matrix mainly depended on the bonding properties between the rigid fiber and matrix.