Experimental Study On Mechanical Properties And Three-dimensional Numerical Simulation Of Hybrid Steel Fiber Reinforced Self-compacting Concrete

Ordinary concrete has the advantages of low tensile strength,high brittleness,low ultimate elongation and serious pollution.The hybrid steel fiber reinforced self-compacting concrete(HSFSCC),which is composed of cement,silica fume,quartz sand and mixed steel fiber,combines the advantages of self-compacting concrete and steel fiber reinforced concrete with high flowability.Good resistance to segregation,clearance through the ability and filling capacity,and high strength and so on.In order to improve the shortcomings of ordinary concrete and adapt to the new market requirements,this paper studies the mechanical properties of HSFSCC and the numerical simulation of meso-level.The main contents and conclusions are as follows:(1)Design of HSFSCC Mix Proportion.The paper puts forward the new concept of average thickness of paste layer and sand-fiber ratio.From the microcosmic point of view,a new mix design method is established,which mainly reflects the influence of the amount of slurry and fiber on the mix ratio.In order to ensure the working performance of the concrete mix,the fluidity test of the slurry with different water-cement ratio is firstly carried out,and the ratio of the slurry to meet the requirements is better.Secondly,the reasonable average thickness of paste layer and sand-fiber ratio are determined.Component content;finally change the fiber volume fraction,optimize the mix design.(2)HSFSCC compressive strength test and flexural strength test study.The compressive strength of concrete cubes and the bending strength test of prism were carried out with different water-cement ratio of 0.14,0.16,0.18 and 0.2.The resultsshow that the compressive strength and flexural strength of HSFSCC are improved and the toughness is improved obviously compared with ordinary concrete.The compressive strength is up to 116 MPa and the flexural strength is up to 18.8MPa.The increase of the strength of concrete is closely related to the characteristics of the hybrid fiber and the strength of the matrix,not the higher the fiber content and the stronger the strength.If the proportion of mixed fiber is not appropriate,it is likely to cause fiber agglomeration,affecting the performance of the mixture and concrete strength.The relationship between the 7-day compressive strength and the 28-day compressive strength of HSFSCC was obtained by experiments.(3)Self-compacting SF90,SF100 ratio and constitutive equation of axial compression.According to the specifications of the concrete mix with the test with,adjust and determine the method to determine the final mix of SF90 and SF100 ratio.The compressive strength is 16.4MPa,the compressive strength is 107.2MPa,and the flexural ratio is 1 / 7.SF100 ratio: water-cement ratio of 0.2,the average thickness of0.08 mm slurry,short fiber content of 0.5%,long fiber content of 1%;the corresponding flexural strength of 18.8MPa,compressive strength of 116.2MPa,6.The axial compressive strength and elastic modulus of the two are obtained by the axial compression test.Due to the lack of rigidity of the experimental equipment,only the rise of the stress-strain curve is obtained,and the corresponding constitutive equation is established.(4)HSFSCC three-dimensional numerical simulation.The three-dimensional model of hybrid steel fiber was established by using MATLAB software.The numerical simulation of ABAQUS was carried out without considering the bond slip between fiber and matrix.The stress cloud of each part of the model was analyzed and compared with the experimental data,The results are within the error range,to achieve the HSFSCC from microscopic analysis to the unity of macroeconomic performance.The effects of different fiber contents and types on the compressive strength of concrete are numerically simulated.The simulation results are in good agreement with the experimental results.