| Based on the large amount of construction and domolision waste(CDW)and natural aggregates use,the recycling of CDW would sovle the series of problems originally to realize the sustainable development of construction.Due to the constituents and the complexity of recycled aggregate concrete(RAC),the materials properties of RAC perform worse than the natural aggregate concrete.In order to improve the properties of RAC,some scholars proposed the confined RAC.The present confinement of RAC includes steel tube and fiber reinforced polymer(FRP),considering the light quality and high strength,corrosion resisitance of FRP,and the low cost,high production,recyclable,low energy dissipation,low density,and good tensile performance of flax fiber,the paper proposed the flax fiber reinforced polymer(FFRP)confined RAC system.Due to the high demands of actual projects in complicated situations,the single confinement materials cannot meet the real demands in actual projects.The paper combined FFRP,steel and RAC to make any material work to their advantage via their cooperative work.The research indicated that the steel tube or FRP-steel tube confined concrete,the thin steel tube plays a role both in lateral and longitudinal confinement,but the steel spiral reinforcement(SR)just works in the lateral confinement,and the confinement performs better and the efficiency of steel is higher.According to the characteristics of FRP confined concrete and SR confined concrete,the paper combined FFRP and SR and proposed compressive behavior of FFRP-SR confined RAC with recycled clay brick aggregate(refered to RAC-RCBA)base on existed research on FRP confined concrete and reinforced concrete,which is a kind of composite materials consisting of SR confined RAC-RCBA and external FFRP tube,namely FFRP-SR confined RACRCBA.Fllowing is the main research work in this paper:(1)The experiments of tensile properties of FFRP and the compressive strength of standard RAC-RCBA cube.The tensile tests of 3,6,9-layer FFRP coupons were carried out to obtain the fundamental mechanical properties of FFRP,as the tensile strength,ruptured longituation and stress-stran curves;The compression tests of standard RAC-RCBA cube were carried out to abtain the normal concrete compressive strength and analyzed in the later tested results.(2)Compressive test of FFRP-SR confined RAC-RCBA.The FRP layers,spiral pitch between ties and the strength of core concrete were selected as the tested variables.The specimens of the compression tests include 30 FFRP-SR confined RAC-RCBA cylinders and 6 unconfined RAC-RCBA cylinders.The loading modes of the tests selected the displacement-control and the axial stress,axial displacement and lateral strain of specimens were obtained by the force sensor,displacement sensor,strain gages.(3)The failure modes and tested results of FFRP-SR confined RAC-RCBA.The whole process from the initial loading stages to the complete rupture of specimens were stated and the failure modes,stess-strain behavior,and experimental results of unconfined concrete and FFRP-SR confined RAC-RCBA were analyzed.The effect of FRP layer,spiral pitch between ties of SR and the strength of core concrete on FFRPSR confined RAC-RCBA were also analyzed.The toughness index was selected to analyze the strength and ductility of FFRP-SR confined RAC-RCBA.(4)The theoretical analysis of FFRP-SR confined RAC-RCBA was carried out.The failure mechanism of FFRP-SR confined RAC-RCBA was analyzed,and some classical models were introduced and the calculated values based on the models were compared with the tested results to find the model of above can predict approximately the behavior of FFRP-SR confined RAC-RCBA according to the relative error and variable coefficient to acquire the appropriate strength model,ultimate strain model and axial strain-lateral strain model,and the application and shortages of each presented models were discussed by compared with the test result finally. |
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