Study On The Mechanical Properties Of Recycled Aggregate Concrete And Members With Construction Waste

With the rapid economic development and high speed urbanization process, the construction industry has gained significant achievement. A lot of wastes of building are produced in the process of construction, structure demolition and after disasters, which can cause environmental pollution. However, the use of recycled concrete, which is researched by many countries, can minimize negative environmental impact in the city and slow the huge consumption of natural resources. The material properties of recycled aggregate concrete, the flexural behavior of recycled concrete beam, the shearing behavior of recycled concrete beam, and the compression behavior of column are studied in the paper with the method of test. The behavior of recycled concrete members are researched with the finite element method at the last of this paper on the basis of constitutive relation of recycled concrete. The research work of this thesis is shown as following:1. Experimental study on mechanical properties of recycled concreteBy the means of test on different replacement percentages of recycled aggregate concrete(ie,0%,30%,50%,70% and 100%).the workability of recycled concrete, the cubic compressive strength of different age(ie,3d,7d,14d,28d and 60d),axial compressive strength, splitting tensile strength, the relationship between stress and strain,elastic modulus and the characteristics of shrinkage deformation under natural curing are analyzed and discussed. Under the same condition with same cement content and same fine aggregate content, the cubic compressive strength of recycled concrete decreased in approximate linearity with the increase of replacement percentages.Under the same strength grade, the axial compressive strength increase slowly with the increase of replacement percentages, while the tensile strength and elastic modulus decrease in approximate linearity with the increase of replacement percentages. Meanwhile, the shrinkage deformation increase with the increase of replacement percentages. The relational formula between cubic compressive strength, axial compressive strength, tensile strength, elastic modulus, shrinkage strain and replacement percentages,corresponding property index of common concrete are built. Basis on the test results, the mechanical property index of recycled concrete with different replacement percentage which has a significant engineering value.2. Experimental study on flexural behavior of recycled concrete beamOn the basis of testing on 6 beams with different concrete strength grade(ie.C30 and C40) and different replacement percentage(ie.0%,50% and 70%),the similarities and difference between common concrete beams and recycled concrete beams are compared. The ultimate moments, deflection, cracking moment and the rule of crack development of recycled concrete beam are analyzed. Based on the mechanical property index of recycled concrete, it is proved that it is feasible to apply the current design standard for ultimate bearing capacity, cracking moment, crack width and deflection of recycled concrete beams, which gives higher calculation accuracy.3. Experimental study on shearing behavior of recycled concrete beamOn the basis of testing on 9 beams for grade C30 with different shear span ratio(ie.1.5,2.5 and 3.0) and different replacement percentage(ie.0%,50% and 70%),the similarities and difference of shearing behavior between common concrete beams and recycled concrete beams are compared. The failure patterns, the main influencing factors of shear capacity and the characteristics of development of cracks are analyzed and discussed. Based on the mechanical property index of recycled concrete, it is proved that it is feasible to apply the current design standard for shear capacity of recycled concrete beams, which gives higher calculation accuracy.4. Experimental study on compression behavior of recycled concrete columnOn the basis of testing on 12 columns with different eccentricity ratio(ie.0,0.343,0.537 and 0.800)and different replacement percentage(ie.0%,50% and 70%),the loading feature, the failure patterns and the main influencing factors of compression capacity are analyzed and discussed. Based on the mechanical property index of recycled concrete, it is proved that it is feasible to apply the current design standard for compression capacity of recycled concrete columns, which gives higher calculation accuracy.5. Numerical analysis of loading behavior of recycled concrete beam and columnWith the nonlinear finite element program ANSYS, the numerical simulation on flexural behavior of beams, shearing behavior of beams and compression behavior of columns are presented, and the mechanical property index and constitution relation of recycled concrete which have been obtained in this paper are introduced into the finite element model. The calculating results agree well with test ones by the comparison between those results, which indicate that the mechanical property index and constitution relation of recycled concrete are reasonable and correct.The research results of this paper provide reference for engineering application of recycled aggregate concrete.