Prediction And Numerical Simulation Of Fiber Distribution In Steel Fiber Self-compacting Concrete

Compared with ordinary concrete,steel fiber reinforced self-compacting concrete(SFRSCC)has more excellent workability and mechanical properties,and it has been increasingly used in engineering structures such as high-rise buildings,bridges,tunnels,and road pavements.Unlike ordinary steel fiber reinforced concrete(SFRC),the orientation and distribution of steel fibers immersed in SFRSCC are affected by many factors and they have have a significant influence on the mechanical properties of concrete.Therefore,it is of critical theoretical importance and engineering application values to study the fiber orientation and distribution immersed in SFRSCC.This paper investigates fiber orientation and distribution immersed in SFRSCC by using combination of experimental research,theoretical analysis and numerical simulation.And a numerical method that can predict and simulate fiber orientation and distribution is developed.The main research contents and outcomes include:(1)A high flowability self-compacting concrete(SCC)containing fly ash was prepared by optimizing the mix ratio design.Slag and steel fibers were added to the prepared SCC and 12 groups of SFRSCC were prepared.The slump flow,V-funnel and L-box test for prepared concrete were performed.And the compressive strength,split tensile strength and flexural strength test for concrete specimens were carried out.The results showed that the concrete mixed with slag and steel fibers basically met the requirements for workability and mechanical properties of SCC.The mechanical properties of SFRSCC containing 30% slag and 0.9% steel fibers were optimized.The compressive strength,splitting tensile strength and flexural strength of this SFRSCC increased by 31.2%,52.3% and 139.8%,respectively.(2)The image analysis technology was used to extract the fiber orientation and distribution on different cross sections of the flexural strength test specimens along the length direction.And the fiber distribution and orientation on the cross sections were quantitatively analyzed by several fiber distribution and orientation coefficients.The results showed that the fiber orientation and distribution on the cross sections of the specimens were not completely three-demensional random,which was affected by the fiber volume content to a certain extent.Increasing the volume content of steel fibers slightly weakened the degree of segregation of steel fibers in the vertical direction and the alignment of the steel fibers along the flow direction,and increase the uniform distribution of steel fibers on the cross sections.(3)A numerical method for simulating the flow of SFRSCC,and fiber orientation and distribution of steel fibers was proposed.The fiber orientation and distribution of the steel fibers in SFRSCC beam of the literatures,and the fiber orientation and distribution of the steel fibers on the cross sections of the flexural strength test specimen of this paper were simulated by the proposed method.Based on the above numerical method,a mesoscale finite element model that can simulate different fiber distribution and fiber-matrix bonding properties was established and this model was used to simulate the flexural test of the SFRSCC in this paper.The results showed that the numerical simulation results were in good agreement with the experimental results,which verified the correctness of the numerical method and the micro finite element model proposed in this paper.When the fiber volume content was constant,the peak strength,peak displacement,toughness and residual strength of SFRSCC increased with the increase of fiber orientation coefficient.(4)The influence of the initial fiber distribution,the rheological properties of fresh concrete and the size of the specimens(including length,width and height)on the fiber orientation and distribution was further analyzed using the numerical method proposed in this paper.The results showed that the optimization of initial fiber distribution before concrete casting can significantly improve the fiber orientation and distribution when concrete cating was finished.Reducing the yield stress of SFRSCC had the effect of optimizing fiber orientation.Among the three specimen sizes,the influence of the specimen length on the fiber orientation and distribution was the most significant,and the specimen width and specimen height had similar influences on the fiber orientation and distribution.