The Study On Distribution Model Of Recycled Aggregates And Waste Fibers

Micromechanics has developed, which uses numerical simulation to study concrete specimens’ bearing capacity, crack propagation and damage morphology, and reflects the mechanism of internal damage and macroscopic damage more directly. As the typical materials which implement the strategy of sustainable development:recycled concrete, waste fiber recycled concrete. It’s a promising research that studies their performance from the microscopic point of view. Based on this, the impact of recycled aggregate and waste fiber distribution on mechanism and mechanical properties of matrix concrete were researched from the microscopic point of view in this paper, recycled aggregate distribution model and discard the fiber distribution model. And recycled aggregate distribution model and waste fiber distribution model were established.For recycled aggregate distribution model, only for recycled concrete whose recycled aggregate replacement ratio is 50% and design strength is C30,20 different two-dimensional microscopic recycled concrete aggregate distribution models were established with CAD and put into ABAQUS to simulate the uniaxial tensile test as well as recycled aggregate distribution uniformity coefficient a were defined, finally the effects of a on recycled concrete tensile properties were obtained. For waste fiber distribution model, only for matrix recycled concrete whose recycled aggregate replacement ratio is 50% and design strength is C30, adding waste polypropylene fibers with volume substitution rate of 0.12% and a length of 15mm,14 different two-dimensional microscopic waste fiber distribution models were established with ABAQUS to simulate the uniaxial tensile test as well as three different waste fiber distribution uniformity coefficients were defined:uniformity coefficient β, gather distribution coefficient y, angle distribution coefficient 2, finally the effects of β, γ, λ on waste fiber recycled concrete tensile properties were obtained.(1)The recycled aggregate distribution model and waste fiber distribution model were built to simulate the uniaxial tensile test, and the simulation results were compared with existing experimental data or theories, whose error were small, so it proved that the simulation method and build model have applicability, putting forward new ideas and direction to further improve the theory.(2)The tensile cracking mechanism of recycled concrete is the same regardless of the recycled aggregate distribution uniformity coefficient a:cracks start with interface and then extend to mortar, and a only affects the crack location and the number of recycled aggregate particles through cracks. But tensile strength and deformation capacity of recycled concrete change regularly with a:for recycled aggregates that distribute moderately, namely, α∈[0.338,0.483], the tensile strength is higher, and the tensile stress-strain curve is divided into elastic stage, plastic stage, steep decline stage and plat decline stage, and the curve is plump with good deformability; For recycled aggregates that distribute either too evenly or too dispersedly, namely, a<0.338 or a>0.483, the tensile strength is lower and the tensile stress-strain curve of the four stages is incomplete or not plump accompanied with small ultimate tensile strain and poor deformation capacity of recycled concrete.(3) Regardless of waste fiber distribution, namely whatever β, γ, λ is, the tensile cracking mechanism of waste fiber recycled concrete is the same:cracks start with matrix concrete and are resisted by waste fiber during launch. But tensile strength and deformation capacity of waste fiber recycled concrete change regularly with β, γ, λ:tensile strength decreases as X increases and the impact is significant, while the tensile strength decreases gently with the increase of β and γ, that is, the more discrete fibers distribute and the more significant fibers hold together, the smaller the tensile strength is; And the peak tensile strain increases as β and γ decreases, that is, the more uniform fibers’ number and pitch distribute, the better deformation capacity of waste fiber recycled concrete is, but λ almost has no effect on peak tensile strain.