Impact Of Steel Fiber On Impact Resistance Of Concrete And Its Mechanism Analysis

As a new type of multiphase composite material,the composite reinforced with steel fiber reinforced concrete has been increasingly used in infrastructure construction with its excellent mechanical properties.To understand the impact of steel fiber on the impact resistance of concrete and the distribution of steel fiber inside the matrix,the impact tests were carried out on steel fiber reinforced concrete round cake specimens by using self-made drop hammer impact test device.5 groups of volume fraction were set up,namely 0,0.5%,0.8%,1% and 1.2%,respectively.The effect of steel fiber on the impact resistance of concrete was investigated by analyzing the toughness and ductility ratio.Results show that the addition of steel fiber could increase the impact performance effectively.The ductility ratio is more than 15% when the steel fiber content(by mass)is 0.8%.The toughness coefficient increases with the increase of the fiber volume fraction.When the steel fiber content is 1.0%,the toughness reaches the maximum value,which is close to 10 times of the standard concrete.The addition of steel fiber could decrease the brittleness of the matrix and improve its plasticity,which delays the crack development,and changes the shape and the number of main cracks as well.Both of the amount of steel fiber and its distribution on the impact section are closely related to the impact toughness of concrete.The fiber dispersion coefficient was used to characterize the uniformity of the distribution of steel fibers.The cracks on the impact surface were observed using a stereo-microscope.The statistical analysis of the fiber distribution in the impact section was conducted,and the crack resistance and toughening of steel fiber reinforced concrete under impact loading were further analyzed.The image processing of the cross-section was performed by the MATLAB binarization command.The number of fibers on the impact section was counted,and the fiber dispersion coefficient was calculated and then fitted.Based on the Weibull distribution,the impact test results were statistically analyzed and different failure rates were established.The results show that the fiber content has a significant improvement in impact properties.In addition,the fiber dispersion coefficient increased with the increase of the dosage.And the two-parameter Weibull distribution could appropriately evaluate its impact performance.