Experimental Research On The Flexural Behavior Of Recycled Coarse Aggregate Concrete Beams

As a new type of sustainable materials, recyled concrete can not only bring environmental benefits, but also has good social and economic benefits, many scholars are needed to experience large numbers of pilot study and repeat verification before the wide application of recycled concrete in practical engineering. Therefore, the compression constitutive relationship with the same strength grade but different replacement ratio of recycled coarse aggregate and the flexural behavior of recycled coarse aggregate concrete beams were studied with experimental method in this thesis. The work are as follows:Firstly, In order to study the mechanical properties of recycled concrete with the same strength grade, three kinds of recycled concrete have been made whose intensities reached C25, C30, C35at the recycled coarse aggregate replacement ratios of0%,50%,100%seperately. And the stress-strain curve test and modulus of elasticity test on the same strength grade of recycled concrete are completed. The variance for failure pattern, peak strain and elastic modulus of recycled concrete which has the same strength grade is analyzed. Studies have shown that the overall shape of recycled concrete’s stress-strain curves is similar to normal concrete’s under the same strength grade, modulus of elasticity decreases with the increase of recycled coarse aggregate replacement ratio, while the peak strain basicly remains unchanged. Fitting curve descent stages of the test results steepened gradually with the increase of recycled coarse aggregate replacement rate.Secondly, the flexural performance test of17recycled coarse aggregate concrete beams with different replacement ratio and reinforcement ratio is done, to study the difference in flexure performamce of the recycled coarse aggregate concrete under the same strength grade. Based on the experimental results, the following conclusions are drawn. Under the same Intensity level, the failure modes and the bending mechanism of recycled coarse aggregate concrete beams were similar to ordinary concrete beam. In bending, the beams experienced significantly three stage:not crack stage before cracking, cracking to the longitudinal reinforcement yield stage and destruction stage. The average strain measured on cross-section obliges to the plane section assumption. Under the same strength grade, the ultimate moment of recycled coarse concrete beams are similar to conventional concrete beam, however, the cracking moment of recycled coarse concrete beams reduce somewhat. In addition, according to the measured constitutive relation, the ultimate bearing capacity calculation formula of recycled coarse concrete beams are discussed. Meanwhile, in the light of present specification for Design of Concrete Structure (GB50010-2010), the cracking moment applicability to recycled concrete beam is discussed.Additionally, the ABAQUS finite element software was used for the nonlinear analysis of test beams. The feasibility of finite element simulation is verified by comparison with experimental data.