Fractal Analysis And Experimental Study On Flexural Behavior Of Rubber Concrete Beams With Different Coarse Aggregate Gradation

Crumb rubber concrete(CRC) made by mixing a certain amount of crumb rubber intoConcrete is one of engineering composite materials, which is characterized by largedeformation,multi-energy dissipation,low elastic modulus and so on.At the same time，itcan relieve environment stress caused by waste rubber by mixing a certain amount ofcrumb rubber into Concrete,which will bring about huge economic benefits and socialbenefits.Most discussed mechanical properties of crumb rubber concrete through Changing thesize of crumb rubber mixed into concrete and the content of crumb rubber. research ofacademic papers on mechanical properties of crumb rubber concrete with DifferentAggregate Gradation are discovered.Coarse aggregate is the main ingredient inconcrete.The gradation of coarse aggregate made a big difference in the aspect ofmechanical properties for normal concrete.The impact of gradation of coarse aggregate onCrumb rubber concrete remains unknown.Normal concrete(NC) and crumb rubber concrete with3different coarse aggregategradation by studied in this master dissertation.Material properties of normal concrete andcrumb rubber concrete with different aggregate gradation are studied in the first place.Thenthe impact of gradation of coarse aggregate on normal concrete beam and crumb rubberconcrete beam in the aspect of the bearing capacity of beam,the development of Surfacecrack,deflection,maximum width of crack and so on.lastly,Surface crack of beam is studiedthrough fractal theory.The main results are shown as follows:1.Differentia of compressive strength of CRC with different coarse aggregategradation is small.The crumb rubber in concrete changed stress mechanism of crumbrubber concrete. The interfacial bond strength from coarse aggregate and cement stonedetermines the strength of concrete for normal concrete,while the interfacial bond strengthfrom crumb rubber and cement stone determines the strength of CRC.Meanwhile,Thecrumb rubber in concrete changed Deformation mechanism of crumb rubberconcrete.Differentia of elastic modulus of CRC with different coarse aggregate gradation islarge.Elastic modulus of CRC with Small particle size of coarse aggregate gradation isleast,and Elastic modulus of CRC with large particle size of coarse aggregate gradation ismaximal.2.Curve of relationship between load and deflection of normal concrete with differentcoarse aggregate gradation have a large deviation.However,Curve of relationship betweenload and deflection of CRC with different coarse aggregate gradation have a very smallgap.Under different coarse aggregate gradation,mixing a certain amount of crumb rubberinto normal concrete improved the ultimate deformation capacity of beam and ductilitywithout exception.Especially,the ultimate deformation capacity and ductility of rubberconcrete beam with small particle size of coarse aggregate gradation is best.In the aspect ofultimate bearing capacity of beams,normal concrete with small and medium particle size ofcoarse aggregate gradation mixed a certain amount of crumb rubber into normal concretedescended,while normal concrete with large particle size of coarse aggregate gradation mixed a certain amount of crumb rubber into normal concrete enhanced.In addition,crumbrubber plays a outstanding role in controlling development of surface crack of beam. CRCcrack develops more slowly.3.The fractal dimension value of surface crack of beams under destruction of beams iscalculated.The fractal dimension value from whole beam area,pure bending section andshear bending section is compared. This study shows that the fractal dimension value fromthis three section of CRC beam with Small particle size of coarse aggregate gradation issame Basically and the other exception.It shows that CRC-small have the best energyconsumption.On the other hand, the fractal dimension value of surface crack of normalconcrete beams is enhanced by mixing a certain amount of crumb rubber into Concrete.Itshows that mixing a certain amount of crumb rubber into normal concrete can advance theenergy dissipation capacity of normal concrete,CRC-small in particular.4.The same quantitative relationships have been established between the characteristicvalues (f, max,S)and the fractal dimension of surface cracks. The study shows that thefractal dimension of cracks grows gradual rapidly with that the accretion of the cracksbreath.The fractal dimension of surface cracks can be taken as one evaluation index of thedamage degree of reinforced concrete. Fractal geometry theory provide a new thought andmethod for study of the cracking and breakage of concrete structures.5.Under comprehensive index,CRC with Small particle size of coarse aggregategradation is the best gradation.