Experimental Study On Static And Dynamic Pull-out Test Of Special-shaped Steel Fiber From Cement Matrix

Due to its excellent mechanical properties,steel fiber concrete has been widely used in the field of engineering construction in my country.However,the weak interface bond between the steel fiber and the matrix makes it difficult to fully exert the crack resistance of the steel fiber.At present,the commonly used method to enhance the bond performance between the steel fiber and the matrix is ??to change the shape of the steel fiber and increase the steel fiber and The mechanical anchoring force between the substrates further enhances the macro-mechanical properties of the steel fiber concrete.This paper conducts a systematic experimental study on the static and dynamic bonding properties of end-hook type steel fiber and spiral type steel fiber to cement matrix,and in-depth study of the pull-out of steel fiber and cement matrix with different embedding angles,embedding depths and pull-out rates behavior.Through analysis,it is found that the two kinds of fibers can only increase the bonding performance with the matrix to a limited extent.In order to better exert the crack resistance of steel fibers,this paper proposes a twisted steel fiber that can be combined with the other two fibers in the cement matrix.Comparing the static and dynamic bonding properties,it is found that twisted steel fibers have obvious advantages in increasing the ultimate bonding strength,fiber utilization,and fiber efficiency.The main research contents and conclusions of this paper are as follows:(1)The static and dynamic bonding performance of the end hook steel fiber and the cement matrix was systematically studied,and the fiber failure mode of the end hook steel fiber and the cement matrix was analyzed.And the influence of bond-slip curve characteristics.(2)The static and dynamic bonding properties of three different sizes of spiral steel fiber and cement matrix were systematically studied,and the effects of embedding angle,embedding depth and pull-out rate on fiber failure mode and bond slip were analyzed in depth.Shift the influence of curve characteristics.According to the experimental data,the influence of the winding diameter and pitch of the spiral steel fiber on the fiber pull-out behavior is studied.Although the buried depth is the same,the steel fiber with a longer winding diameter and pitch will require a larger pullout load during the pull-out process.At the same time,it is found that the fiber with larger winding diameter needs a larger slip value to increase the same load during the extraction process,while the fiber with a larger pitch requires a smaller slip value to increase the same load during the extraction process.(3)This paper conducts a systematic experimental study on the static and dynamic bonding properties of twisted steel fibers and cement matrix,and analyzes the different embedding angles,embedding depths and pull-out rates between the end hook steel fibers and the cement matrix on the fiber failure mode And the influence of bond-slip curve characteristics.At the same time,compare the slip curves of the three types of steel fibers at the same embedding angle,embedding depth and extraction rate.(4)According to the fiber pull-out test data,a comparative analysis of three different types of steel fibers in terms of fiber efficiency and fiber utilization rate shows that the bonding performance between twisted steel fibers and the matrix is??more advantageous.In addition,through the uniaxial tensile test,the ultimate tensile strength and fiber pull-out power consumption of the hook-shaped steel fiber and the twisted steel fiber are compared to further confirm the advantages of the twisted steel fiber.