Experimental Study And Numerical Simulation Of Early Crack Of Recycled Coarse Aggregate Concrete

Coarse aggregate is the preparation of concrete raw materials essential,natural sand coarse aggregate existing has been difficult to maintain the sustainable development of the coarse aggregate concrete,it is necessary to find a suitable substitute for natural aggregate.The whole earth every year because of the old road,and old building demolition waste concrete in large scale,the waste concrete can not effectively recycling,so the research on the properties of recycled concrete is very important.After the mechanical crushing and grading of the waste concrete blocks,the recycled coarse aggregate can be made according to a certain substitution rate and the corresponding mix proportion.Now the research is mostly mechanical properties of recycled coarse aggregate concrete,and Research on early cracking and early cracking of steel fiber recycled coarse aggregate concrete of recycled coarse aggregate concrete is less and less,while the test complexity and high cost and limited the development of recycled concrete,as a kind of numerical simulation method of finite element analysis the numerical is easy and intuitive and save test cost.Therefore,the main contents of this paper are as follows:(1)the constraint plate method and measured data using a universal testing machine and the crack width observation device,through the analysis of the experimental data,the influence of different recycled coarse aggregate replacement of natural aggregate ratio,amount of different volume fraction of steel fibers on the recycled coarse aggregate concrete compressive strength of 28 days and early cracking performance,the main conclusions are as follows:with recycled coarse aggregate replacement rate increased,28d,28d compressive strength of recycled concrete anti cracking strength,showed a trend of first increase and then decrease,when the replacement rate is 60%,the compressive strength reached a maximum value;with recycled coarse aggregate replacement rate increased.Recycled concrete 24h evaporation rate,maximum crack width and total area decreased first and then increased.When the replacement ratio of recycled coarse aggregate to natural aggregate is 60%,the degree of cracking of recycled coarse aggregate concrete slab is the smallest.The steel fiber recycled coarse aggregate concrete in the 28 days compressive strength increased with the increase of volume fraction of steel fiber,and decreased the rate of water evaporation;24h,maximum crack width and the total area of the overall performance of the first decreased and then increased trend.The 28d splitting strength of recycled coarse aggregate concrete slab increases with the increase of steel fiber volume fraction.When the volume fraction of steel fiber is up to 0.8%,the initial cracking degree of steel fiber recycled coarse aggregate concrete slab is the smallest.(2)through ANSYS finite element numerical simulation,first select the Solid70 unit of the thermal analysis,thermal analysis is completed,the Solid70 unit into Solid45 unit,read the results of thermal analysis,structural analysis,obtained the recycled coarse aggregate concrete slab temperature stress.After the thermal stress,the finite element model is established,and the Solid65 element is used to analyze the structure of the steel fiber.The amount of calculation and analysis of different volume fraction of steel fiber recycled concrete slab on the effect of early cracking of steel fiber,the numerical simulation results show that steel fiber recycled concrete early cracking plate occurred near the crack in the induction,with the increase of volume fraction of steel fiber,model plate crack number decreased first and then increased.When the volume content of steel fiber reached 0.8%,a finite element model of plate cracking at least;when the volume fraction of steel fiber is 1.2%,although the board did not crack along the crack model induced by distribution,but the largest number of cracks.Through experimental study on early cracking of recycled coarse aggregate concrete and steel fiber recycled coarse aggregate concrete,the early crack is simulated by ANSYS steel fiber recycled coarse aggregate concrete,the test results and numerical simulation results,to provide support to the engineering practice of recycled coarse aggregate concrete.