Experimental Study On Crack Resistance Of Different Thickness Hybrid Fiber Recycled Concrete Beams

In this paper,fly ash and micro silicon powder instead of parts of the cement and recycled aggregate made of waste concrete instead of part of the natural aggregate,with which recycled concrete are mixed.Meanwhile we change mixing rate of different combinations among the imitation of steel fiber the length-diameter ratio is smaller with the basalt fiber length-diameter ratio is bigger and different thickness,then analyzes the influence on basic mechanical properties of hybrid fiber recycled concrete and the influence of beam crack resistance of the specimens.The main research content is as follows:First of all,by changing the combination rate of fibers,the study analyzes that influence on the basic mechanical properties of recycled concrete and some properties of beams,including failure mode,emphasis on cracking behavior,initial cracking and yield load,load deflection curve,the tensile steel cross strain,and the condition of concrete strain under initial cracking and yield.The test showed that the fiber can improve the mechanical properties of recycled concrete,the splitting tensile strength of recycled concrete to improve is more obvious;at the same time,the fiber can effectively restrain the crack of recycled concrete beams,the group F3,3Bi test beam get good anti cracking effect.Secondly,by changing the thickness of recycled concrete layer,the study analyzes its influence for crack resistance of recycled concrete beams.The test shows that the crack resistance of the beam is obviously improved with the increase of the recycled concrete layer thickness of the hybrid fiber.That is to say,at the early loading stage of beam,the thickness of the layer has little effect on the crack resistance of the beam.During the late loading stage,with the increase of the thickness of the hybrid fiber recycled concrete,the fiber layer prevented cracking,slowed down the cracking speed and deformation,and improved the crack resistance of the beam gradually.But after the thickness of 90mm,the increase of the crack resistance of the beam is not significant.Then,through theoretical calculation and analysis of the crack resistance of recycled concrete beams with different thickness and hybrid fiber,the theoretical analysis and experimental results are compared and analyzed,from this the correction formula for maximum crack width and maximum deflection of beam is proposed.Finally,the ANSYS finite element analysis software is used to simulate and analyze the hybrid fibers recycled concrete beams with different thickness of layers.It is concluded that the failure state and crack development condition of the simulation beam are consistent with the actual test results.The simulated values of initial cracking load and yield load of beams are basically consistent with the experimental values.