Research On Mechanical Properties Of Large Recycled Aggregate Filled-Concrete

Large recycled aggregate filled-concrete is a new technology of environmental protection and energy saving which can effectively deal with construction waste on the basis of three kinds of concrete,self compacting concrete and recycled concrete.At present,the research on recycled large aggregate self compacting concrete is still in the initial stage.The research on construction method and sample quality control is in blank,and the experimental data based on mechanical properties are seriously insufficient.It is difficult to provide effective and credible guidance to the practical application of regenerated large aggregate self compacting concrete.In order to solve these problems,the following work has been carried out:The pouring method of rock filled-concrete is improved,and the influence of the mass of the large recycled aggregate under the water content of 0% and 100% is studied.Under the condition of the replacement rate of 0%,20%,40%,6 cubes with a side length of 450 mm and three 450 × 450 × 900 mm prism are made,and the whole experiment and cutting are adopted.The compression performance of the large aggregate filled-concrete is studied by sampling method,and the feasibility is explored by numerical simulation based on the finite element mesh model based on digital image processing and real data,and 4 flexural members with 450 x 300 x 2700 mm are made under the condition of different replacement rate of gross stone,and 4 points are subjected to bending.The bending performance of the flexural members is studied and the structural reliability of the flexural members is evaluated based on MATLAB and JC method.Through the study of this paper,we can draw the following conclusions:(1)The water absorption of large recycled aggregate is strong and water pumping effect will be produced when pouring.With the increase of water content,the pumping effect is weakened and the quality of pouring is improved.The quality of pouring can be effectively improved by soaking and reproducing large aggregate before pouring.(2)Under the condition of uniaxial compression,the failure process of the specimen is similar to that of the ordinary concrete,but the stress retention stage will appear in the forthcoming destruction;with the increase of the rate of replacement of the stone,the cracks in the block show a phenomenon that the secondary cracks increase,the crack development trend is changeable,the crack opening path is discontinuous,and the different Mao Shiqu is different.Under the replacement rate,the ultimate compressive strength of recycled aggregate concrete with strength of C20 is 15.6~24.2MPa.(3)The simulation results of the finite element mesh model based on the digital image processing and the real data can be consistent with the actual experimental results,and the applicability is good.The simulation results show that the failure mode of the test block is mainly shear failure.(4)The reinforced and unreinforced large recycled aggregate filled-concrete flexural members all conform to the assumption of flat section;with the increase of the replacement rate of the gross stone,the cracking load of the flexural member decreases,the ultimate load increases,the secondary cracks increase and the crack continuity weakens;the cracking load of the experimental component under the different substitution rate of the rock and stone 0.61~0.76 is the calculated value for ordinary concrete specification,and the ultimate load is 0.87~0.94 of common concrete specification.(5)the reliability index of the large recycled aggregate filled-concrete flexural member is between 3.5 and 6.3,which is lower than the reliability index of the ordinary concrete,and it can meet the class two safety grade of the national building structure.