Study On Performance Optimization And Pilotscale Experiment Of Low-strength Flowable Backfill Materials Made Of Construction Waste

With the increasing amount of urban construction waste in our country,its recycling is becoming more and more important.At present,granular construction waste materials with size larger than 4.75 mm have been used for the production of cement stabilized road base material,but those smaller than 4.75mm(hereinafter referred to as the fine material of construction waste)contain waste brick particles,dust,becoming "secondary rubbish" with no use,hindering the development of the construction waste to be recycled,because of their complex composition and uns Table performance.At the same time,some parts of the backfill can not be effectively compacted in the road construction and maintenance,such as retaining wall back,upholding abutment back,resulting in deformation,subsidence and other damage.This paper utilizes the fine material of construction waste.Namely,the construction waste generated by the particle size which is less than 4.75 mm of eventual waste,researches into and exploits a new self-compacting backfill material that has the advantages of low cost and fast backfill.Optimize the performance of the fine material of construction waste and rely on the pilotscale experiment to put forward a kind of new ways of recycling for construction waste.This article mainly discusses four aspects of the flowable backfill materials made of construction waste which are performance optimization,mechanical property,endurance quality,pilotscale experiment.The main research and conclusions are as follows:(1)To optimize the mixture ratio design,liquidity and secrete water resistance change law is discussed.By adding bentonite,reduceing bleeding rate to improve the work performance.It is suggested that the best content of bentonite is 1% of the construction waste.Because of its inhibition on the fluidity,the proportion should not be too much.(2)Laboratory tests on its mechanical property include unconfined compressive strength test,stress-strain test,bearing capacity(CBR)and penetration resistance,penetration ratio test.Text explored the relationship among age,water solid ratio,sand ratio,admixture and strength.Research into characteristics of stress-strain full curves and the material constitutive equation curve is obtained;establishing the relationship among the material penetration resistance,penetration rate and indoor CBR to provide the basis for the actual project through the backfill material field test of penetration resistance and penetration ratio into indoor CBR.(3)The endurance quality is studied by dry-wet cycle test and freeze-thaw cycle test.Under dry-wet cycles and freeze-thaw cycles of two different external damage conditions,the test results show that the materials have the similar deterioration: with the increase of compressive strength,resistance to environmental damage also increased;the fly ash is helpful to improve its ability to resist damage;when the sand ratio is higher than 0.10,the dry-wet and freeze-thaw resistance durability meet the project requirements;the strength attenuation prediction formula of dry-wet and freezethaw are established by regression analysis.(4)The basis for the construction process and technology of the material is provided by carrying out pilotscale experiment.In the process of pilotscale experiment,construction technology for the whole construction process is simple and easy to grasp from the procedure of the mixing and pouring to the performance test.Moreover,the test method for the performance of the material can be used to control the construction quality.