Experimental Research On Micromechanical Properties Of Interface Between Fiber And Cement Mortar In Fiber Reinforced Concrete

As a typical heterogeneous composite building material,there are five factors contribute to the mechanical properties of fiber reinforced concrete at the microscopic level,including the characteristics of three main components of the material(aggregate,mortar and fiber),interfacial properties between mortar and aggregate and interfacial properties between mortar and fiber.The thesis mainly studies on the interface between fiber and cement mortar performance by experiments,analyzes the effect and influence of fiber in concrete,and at last reveales the strengthening and toughening mechanism of fiber reinforced concrete.The main work and research results are as follow:There are four kinds of concrete were prepared with the same standard mix,including ordinary concrete,polyvinyl alcohol(PVA)fiber reinforced concrete,basalt fiber reinforced concrete and glass fiber reinforced concrete.The macroscopic mechanical properties of concrete were tested by experiments,it was found that compressive strength of concrete cubes,axial compression strength and elastic modulus decreased while splitting tensile strength and flexural strength improved significantly with the incorporated of PVA fiber,and the toughness of concrete had greatly improved at the same time.However,with the incorporation of basalt fiber or glass fiber,the concrete cubes compressive strength,axial compressive strength,elastic modulus and splitting tensile strength of the composite material all increased,but its splitting tensile strength increased less than PVA fiber reinforced concrete.According to the compression-shear and tensile mechanical properties test about the interface between fiber and cement,parameters of interface mechanical properties were gotten and figured out the interface destroy criterion.According to the experimental results,it was found that the bond strength of the interface between PVA fiber and cement mortar was higher than basalt fiber or glass fiber.In the interface compression-shear mechanical performance test,the destroy mode of the specimen changed from the interface destroy to mortar crushing as the interface angle ? exceeded60°.The electron microscope scanning test found that the interface transition zone between aggregate and mortar interface of PVA fiber reinforced concrete was more loose than in ordinary concrete,which showed that PVA fiber had the effect of air-entraining.With the water-cement ratio decreased,the dense degree of the interface transition zone between three kinds of fiber and mortar was increased,therefore theinterface tensile and shear strength increased with the water-cement ratio decreased as well.In addition,fibers ran through the micro cracks in concrete and limited the expansion of cracks,therefore concrete toughness and tensile properties were improved because of the incorporate of fibers.