Experimental Study On Bond Behavior Between Recycled Concrete And Rebars

With the acceleration of urbanization in China,a large number of waste building materials are produced.In order to avoid secondary pollution,the research and application of recycled concrete made from waste building materials are the inevitable outcome of saving resources,protecting human living environment and maintaining sustainable development of society.The research of mechanical properties of reinforcing bar and recycled concrete has even more extensive application prospect.Based on this,this paper combines experimental methods with theoretical analysis to analyze the bond behavior of rebar and recycled concrete based on reinforced concrete bonding theory and verify its constitutive relation.Firstly,the strength of C30 and C40 is taken as the strength index of recycled concrete.Seventy-two specimens of 150mm×150mm×150mm cubes with replacement rates of 0%、20%、40%、60%、80% and 100% of recycled aggregate were prepared with 16 mm and 20 mm ribbed rebar as the specimens for the central pullout test of rebar and concrete.At the same time,thirty-six specimens of150mm×150mm×150mm cubes were prepared for the compressive strength test of recycled concrete cubes.According to the test results,the bonding stress of RC40 is greater than that of RC30 in pulling out the unit slip value,and the bonding effect of RC40 is better,and the slip value of pullout test of 16 mm specimen is much less than that of 20 mm specimen.When the replacement rate is 40% for C30-16 mm,C30-20 mm,C40-16 mm and C40-20 mm specimens,the replacement ratio of recycled coarse aggregate has the most favorable optimization effect on the slip impact factor.Secondly,based on the testdata,the factors affecting the replacement rate of recycled coarse aggregate,rebar diameter,bond stress and relative bond stress are considered as relevant variables.Based on the regression analysis of experimental data,the functional expressions of the compressive strength of recycled concrete,the bond strength between the diameter of rebar and recycled concrete are derived under the condition of more suitable replacement ratio of recycled aggregate;the application of load-slip curve between reinforced concrete and recycled concrete is verified by comparing the parameters of the relation between the components ofreinforced concrete and concrete.Finally,based on the results of the pullout test,the finite element analysis of the bond stress between the steel and the recycled concrete is further carried out.Due to the influence of more factors on the bond strength,the regenerated concrete RC30 and RC40 and 16 mm ribbed steel bar with 20 %、 40 % and 100 % representative replacement rate of regenerated coarse aggregate were considered as the main research object,and a finite element analysis model were established for the bond strength of a new composite aggregate reinforced concrete with precise three-dimensional solids in conformity with the shape of ribbed deformed steel bars,three-dimensional nonlinear finite element analysis was carried out for the recycled concrete pullout test with ANSYS software.Compared with the actual test results,the mechanical properties,stress-strain law and rationality of rebar and recycled concrete are further verified.