Study On Mechanical Properties Of Steel Fiber And PVA Fiber In Concrete

Fiber-reinforced cementitious material is a composite material by mixing fibers into cementitious material,which has strain-hardening characteristics that ordinary cementitious material does not have.This paper mainly studies the mechanical properties of steel-polyvinyl alcohol hybrid fiber concrete,by mixing different steel fibers and polyvinyl alcohol fibers into cementitious material to form a fiber-reinforced cementitious composite material,to conduct several mechanical experiments,with the purpose of studying The purpose is to find out the high strength and high impermeability of hybrid fiber concrete that can overcome the defects of ordinary cement base material such as brittle and easy to crack,and further analyze the effect of different varieties of fibers and different proportion of fiber admixture on the concrete performance.According to the engineering practice and related literature,this paper selected 0.3%,0.6%,0.9% three kinds of total fiber blending,through the polyvinyl alcohol fiber and steel fiber respectively single blending,mixed with different proportions(1:1,1:2,1:4)to study the mechanical properties and durability of composite reinforced cementitious materials,concrete compressive test,concrete splitting tensile strength test test,concrete flexural strength test and concrete resistance to chloride ion permeability test,and the experimental results obtained were analyzed.Steel-polyvinyl alcohol mixed fiber concrete 28 d compressive strength test study found that the single admixture of steel fiber on the concrete compressive strength increase the most,polyvinyl alcohol fiber will reduce the compressive strength of concrete to a certain extent,mixed fiber concrete compressive strength compared to the single admixture of steel fiber concrete slightly lower,1:4 mixed fiber concrete compressive strength increase the most effect;concrete splitting tensile strength test study It was found that steel fiber can significantly improve the splitting tensile strength of concrete,the effect of polyvinyl alcohol fiber on the tensile strength of concrete shows a trend of first growth and then decrease,1:2 mixed fiber concrete splitting tensile strength growth is the most rapid;concrete flexural test research found that steel fiber and polyvinyl alcohol fiber can improve the flexural strength of concrete to a certain extent,polyvinyl alcohol fiber and steel fiber to 1:4 mixed with The flexural strength of the concrete matrix is the largest.From the perspective of bending performance,an R-curve method based on fracture mechanics was borrowed and the R-curve calculation was modified to improve the predictability of the performance of mixed fiber concrete.Therefore,I conducted a three-point flexural test on pre-cut beams for mixed fiber concrete with the aim of predicting the axial tensile properties of fiber mixed concrete instead of uniaxial tensile tests.The chloride ion permeability test study found that the chloride ion diffusion coefficient of concrete varies with the dry and wet cycle period and the fiber admixture amount.The matrix impermeability decreased when the fiber admixture was 0.3%,and increased significantly when the fiber admixture increased from 0.6% to 0.9%,indicating that the appropriate amount of fiber admixture can enhance the microstructure of concrete,and the fibers are tightly bonded in the cement matrix to reduce the internal pores of concrete and enhance the integrity and compactness of fiber concrete.Scanning electron microscopy(SEM)was used to observe the mixed fiber concrete,and it was found that the microstructure of concrete after fiber incorporation had lower porosity and higher compactness,and the mixed fiber cement matrix and hydration products were tightly bonded.This observation indicates that the durability of the steel-polyvinyl alcohol hybrid fiber concrete is as expected.