Influence Of Macro Fibers On Permeability And Crack Totuosity Of Concrete

In order to evaluate the influence of the incorporation of macro fibers(steel fiber andpolypropylene fiber)on the toughness,permeability,crack geometry and fractal dimension of the section of concrete from the aspects of post-crack toughness and impermeability of concrete.In this paper,the workability of concrete(slump,gas content),mechanical properties(compressive strength,flexural toughness),splitting test and 3D section scanning were studied comprehensively.The main contents of this paper are as follows:(1)Through the test of workability(slump,gas content),the influence of different macro fibers on the workability of concrete was studied,and try to building the relationship between the different macro fibers and fractal dimension.(2)The influence of fiber on the mechanical properties of concrete was studied through the tests of compressive strength and four-point bending toughness of beam,the mechanical and toughness indexes of beams were calculated and the improvement of flexural toughness of fiber was analyzed,the number of fiber roots in the section of beams was counted to contact with energy absorption values T600,T150。(3)Based on splitting test,the permeability coefficient of concrete with different marco fibers and two kinds of specimens with different thickness under loading was calculated,and the surface crack morphology(zigzag degree)is calculated,and the factors affecting the permeability of concrete were studied.(4)The different specimen section was obtained by 3D section scanning device,and the3 D image was built by Matlab.The fractal dimension D of section was calculated by the improved cube covering method,and the fiber root number of different section is counted.The relationship between fractal dimension and fiber root number,fiber content,working performance and mechanical properties was established.(5)Based on Darcy’s law and percolation cubic law,the relationship between effective crack width and correction coefficient in parallel plate model under different fiber conditions is analyzed systematically,and the relationship between fractal dimension and permeability coefficient under different crack width was analyzed.The empirical formula for reference was also established.