Study On Flexural Property Ang Uni-axial Compressive Stress-strain Curve Of Aligned Steel Fiber Reactive Powder Concrete

The addition of steel fiber can effectively improve the mechanical properties of reactive powder concrete(RPC).However,steel fibers distributed in the matrix of SFRPC were at random,and the reinforcement efficiency is low.In order to give full play to enhancement and toughening effect of steel fibers,this paper presents the preparation method of ASFRPC by using external uniform electromagnetic field.From the microscopic view,the flexural-tensile constitutive models of ASFRPC and SFRPC are established by analyzing single steel fiber pullout model,the probability density function of effective length,the random distribution function of the fiber and complex composite mechanics theory.The flexural tensile property and uni-axial stress-strain curves of the specimens are studied by the following two tests.(1)Four-point bending test.The effects of water binder ratio,steel fiber content,fiber aspect ratio and distribution direction(random,aligned)on flexural tensile properties of the specimens were investigated.The flexural toughness of the specimens were analyzed and compared by two different evaluation methods.Additionally,comparison of the initial crack properties,load-bearing capacity and flexural tensile strength of the elements are carried out.(2)Uni-axial compression test.The compressive stress-strain curves of the specimens were studied in terms of the content,fiber aspect ratio and distribution direction(random,aligned).And the failure mode and compressive strength of the specimens are analyzed.The results show that the flexural tensile strength and flexural toughness of specimens increase with the orientation coefficient of steel fiber.However,the initial crack property of elements depends on the strength of the matrix themselves.For the specimens with the same water binder ratio,steel fiber content and aspect ratio,the flexural tensile strength of ASFRPC is significantly greater than that of normal SFRPC.Indeed,for the specimens with the same water binder ratio,steel fibre content,the flexural tensile properties of the specimens are effectively improved with the increase of fiber aspect ratio.The experimental results show that the ascending section of the compressive stress-strain curves are in good agreement with the theory,and there is a great difference in the descending section of the specimens.Additionally,most of the ASFRPC finally showed split failure mode,while SFRPC showed shear failure mode.