Experimental Study On Flexural Behavior Of Recycled Concrete Beams Made With Manufactured Sand

In recent years,with the advancement of urbanization and the increasing demand for concrete,natural sand resources have become increasingly scarce,and the accumulation of waste concrete has become more and more serious.Under the concept of green and sustainable development,the concrete made with manufactured sand and recycled coarse aggregates began to be researched and applied.As a new material for building,the use of recycled concrete with manufactured sand can not only protect natural sand resources,but also recycle waste concrete,which is environmentally friendly and economical.Compared with natural aggregate,recycled coarse aggregate has its own defects and poor performance.The characteristics of machined sand aggregate and natural sand are also different.The performance of machined sand recycled concrete prepared by the two has not yet been mastered.Therefore,before popularizing the application of machinemade sand recycled concrete,it is necessary to conduct experimental and theoretical studies on its mechanical properties and component properties.In this paper,recycled coarse aggregate and limestone manufactured sand(9.65%stone powder content)are used.On the basis of mix proportion design method of common concrete,the amount of aggregate is determined by ideal gradation model,the recycled concrete with different recycled coarse aggregate replacement ratio(0%,30%,50%,70%and 100%)under the same strength grade is made.The difference in mechanical properties between recycled concrete with manufactured sand and common concrete was studied.And on this basis,the flexural performance test of the concrete test beam was completed,and the mechanical characteristics and failure rules of the recycled sand concrete beam were grasped.The main work is as follows:(1)The mechanical properties of cube compression,modulus of elasticity,splitting tension,prismatic compressive and bending resistance were tested on 147 specimens.The results show that the failure mode of mechanical specimens of recycled concrete with manufactured sand is similar to that of common concrete.With the increase of recycled coarse aggregate replacement ratio,the axial compressive strength and cube compressive strength increase first and then decrease.The splitting tensile strength,modulus of elasticity and flexural strength decrease with the increase of recycled coarse aggregate replacement ratio,when the replacement rate is 70%,the strength increases instead of decreasing.Finally,based on the test results,the conversion relationship between mechanical indexes of recycled concrete with machine-made sand is established.(2)The test results of flexural properties of four concrete test beams show that the deformation,crack development,stress-strain change and beam failure characteristics of recycled concrete beams with manufactured sand are basically the same as those of common concrete beams.The calculation formulas of plane section assumption,ultimate bending moment and deflection in the current code for design of concrete structures(GB50010-2010)are applicable to the beams of recycled concrete with manufactured sand.The cracking moment of recycled concrete beams with manufactured sand is lower than that of nature sand recycled concrete beam and ordinary concrete beam.The approximate calculation method of cracking moment proposed by Professor Guo Zhenhai is applicable to the recycled concrete beams with manufactured sand and is safe.(3)Four concrete beams were simulated by finite element software.According to the mechanical performance test results,using different concrete constitutive relations,the established model was subjected to stepwise loading test simulation.The results show that the finite element software ABAQUS can be used for the numerical simulation of recycled concrete beams with manufactured sand.The numerical simulation results are in good agreement with the experimental measured data.