Experimental Study And Meso-finite Element Analysis Of Flexural Properties Of Fully Recycled Coarse Aggregate Concrete Beams

In recent years,the renovation of urban and rural buildings has accelerated significantly,old buildings have been demolished,and new buildings have appeared in large numbers,resulting in excessive construction waste and overwhelming the environment.As a green and environmentally friendly cement-based material,recycled concrete is prepared by mechanically crushing construction solid waste and separating the recycled aggregate,which can effectively solve the problem of concrete construction solid waste pollution.As an important factor,the substitution rate affects the mechanical properties of recycled concrete.The higher the ratio,the more obvious the difference in concrete properties.All-recycled coarse aggregate concrete can effectively alleviate the current situation of insufficient construction solid waste absorption capacity,and can effectively promote the resource utilization of construction waste,which is expected to become a new direction for the development of recycled concrete.At present,the flexural mechanical properties of concrete beams are made entirely by recycled coarse aggregates,and the flexural mechanical properties are rarely studied by scholars,and the lack of relevant test results will limit the application and promotion of this technology.This paper adopts the method of combining experiment and numerical simulation.Taking the replacement rate of recycled coarse aggregate,the volume fraction of steel fiber,the degree of pre-damage,and the reinforcement of carbon fiber cloth as the test parameters,five full-scale concrete beams were designed,including one natural concrete beam and four fully recycled aggregate concrete beams.The failure process,deflection change,bearing capacity and other bending performance laws of each specimen.According to the test data of the mechanical properties of the member materials and the calculation formula of the flexural bearing capacity of the normal section of the concrete beam in the current specification,the specification value of the flexural bearing capacity of the fully recycled coarse aggregate concrete beam is obtained,which is compared and analyzed with the test value to verify the application of the specification formula sex.Based on the ABAQUS general finite element analysis software platform,using Python language program to write the background processing code,select the appropriate constitutive relation,establish the meso-scale finite element model,verify its effectiveness,and then expand the analysis of the flexural performance of concrete beams under different parameters.The main conclusions of this paper are as follows:(1)The failure pattern of the normal section of the fully recycled coarse aggregate concrete beam is similar to that of the natural concrete beam,and all the specimen beams are damaged by appropriate reinforcement;if the recycled coarse aggregate is added,the damage of the specimen beam is more serious,and the number of cracks is slightly smaller.More than ordinary concrete beams,the height and width of cracks have increased;the specimen beams with steel fibers are less broken than the specimen beams without fibers,and the number of cracks is slightly more;carbon fiber cloth reinforcement can improve the cracks of the specimens.The failure morphology,manifested as a decrease in the number and extension height of cracks.(2)Compared with ordinary concrete beams,the flexural rigidity of recycled concrete beams is significantly reduced,the peak bearing capacity is slightly reduced,the deformation capacity after the peak point is poor,and there is obvious brittle failure;adding steel fibers can improve the flexural rigidity of the specimen beams and deformation ability,and improve the brittle characteristics;after reinforced with carbon fiber cloth,the stiffness of the specimen beam is significantly improved,the peak load increases,and the deformation ability is better.(3)Based on the material test data,combined with the calculation formula of the flexural bearing capacity of concrete beams in the current code,the calculation formula of the bearing capacity is modified by introducing the reduction factor of concrete strength.The bearing capacity can be better calculated.(4)Using the Python programming language and ABAQUS finite element software as the platform,the finite element mesoscopic model of the fully recycled coarse aggregate concrete beam was established.The analysis results obtained from the simulation were in good agreement with the experiments.The effect of beam mechanical properties.