Research On Flexural Performance Of High Ductility Recycled Powder Concrete(HDRPC)Beam

With the development of urbanization,the improvement of people’s living standards has also brought many environmental problems because of more and more construction waste generated after demolition.At present,a large number of powders generated in the demolition and construction process are generally treated by landfill or unplanned dumping,which has a serious negative impact on society and environment.In order to realize the resource utilization of construction solid waste,this thesis takes recycled powder as the research object,and explores the feasibility of preparing high ductility recycled powder concrete(HDRPC)as an admixture.The main research contents and results are as follows:(1)Study on the properties of HDRPC materialsThe preparation process and basic properties of recycled powder were explored,and its microstructure,chemical and mineral composition,particle size distribution,burning loss and moisture content were mainly studied.The appearance of recycled powder is similar to cement,However,there are many sharp angles and irregular edges in its morphology,and many small particles accumulate on the surface.This may have a negative impact on the working performance of the recycled powder slurry;The oxide and particle size distribution of the recycled powder are similar to those of cement and fly ash.The mineral composition of the recycled powder is slightly different from that of cement and fly ash.It is confirmed that the recycled powder can be used as an admixture to partially replace cement.(2)HDRPC mix designThrough five factors(water-binder ratio,sand-binder ratio,recycled powder content,PVA fiber content and water reducing agent content)four-level non-interactive orthogonal test,this thesis studies the working performance and mechanical properties of HDRPC,and explores the influence of different factors on the basic performance of HDRPC.1)Working performance.The order of factors affecting HDRPC fluidity is: PVA fiber content> water-binder ratio> recycled powder content> sand-binder ratio> water reducing agent content.HDRPC fluidity was negatively correlated with fiber content and recycled powder content;Water binder ratio,recycled powder content and fiber content are the main factors affecting the water retention of HDRPC.2)Compressive strength.The order of influencing factors on 28 d compressive strength of HDRPC is water-binder ratio> water reducing agent> recycled powder content> sand-binder ratio> PVA fiber content.The water-binder ratio is the main factor affecting the compressive strength of HDRPC,followed by the recycled powder content.When the recycled powder content is 25%,the strength of the specimen is higher.3)Tensile strength.The order of the influence of various factors on the tensile strength of HDRPC 28 d is water binder ratio> PVA fiber content> recycled powder content> water reducing agent> sand binder ratio.Water-binder ratio is also the main factor affecting the tensile strength of HDRPC at different ages,and PVA fiber content and recycled powder content are secondary factors affecting the tensile strength of HDRPC.When the PVA content is 1.5%,the tensile strength is the largest.When the recycled powder content is 25%,the tensile strength has the best promotion effect.With the increase of the content,the strength decreases.4)Tensile strain.The order of influence of various factors on HDRPC 28 d ultimate strain is recycled powder content> water-binder ratio>PVA fiber content> water reducing agent >sand-binder ratio.The recycled powder is the main factor affecting the 28 d ultimate strain of HDRPC specimen,and the increase in its content is conducive to the improvement of strain.5)The working performance and mechanical properties of HDRPC were comprehensively analyzed,and the optimal mixing ratio of HDRPC was given.(3)Flexural performance of HDRPC beamIn this thesis,the difference of bending performance between ordinary concrete beams and HDRPC beams and the influence of different reinforcement ratios on the bending performance of HDRPC beams are studied.1)The bending failure process of HDRPC beam is basically similar to that of ordinary concrete beam,However,the failure of ordinary concrete beams is that the crushing of concrete in the compression zone is relatively sudden and the damage is large.The damage degree of HDRPC beam is small,and the specimen has a certain degree of ductility.2)HDRPC material has excellent tensile toughness,so HDRPC material can partially bear the tensile steel stress and improve the flexural capacity of the beam,thus improving the flexural performance of the test beam.3)Compared with the wide and thin cracking characteristics of ordinary concrete beams,HDRPC presents a fine and dense multi-crack cracking form,which fully reflects the good crack control ability of HDRPC.