Compressive Behavior And Size Effect Of Flax Fibre Reinforced Polymer(FFRP)encased Recycled Aggregate Concrete(RAC)with Partially Clay Brick Aggregate(CBA)

With the development of society and economy,the construction waste has lead great influence to the environment.Recycled concrete is one of the effective ways to solve the environmental problems caused by construction waste.However,the strength and ductility and other mechanical properties of the recycled concrete are lower than ordinary concrete,which has resulted in a great difficulty to the popularization and application of the recycled concrete.Fibre reinforced polymer has the advantages of high strength,high rigidity,good corrosion resistance.Currently,the synthetic fibre,such as carbon fibre(CFRP)and glass fibre(GFRP),are most used fibre material.Although the synthetic fibre has good mechanical properties,it is expensive and it can not be degraded,which are unable to meet the requirements of sustainable development.Compared with the synthetic fibre,the natural fibre has advantages of low price,low density,high strength,no stimulation to the body,low energy consumption and degradation,the application of natural fibre in civil engineering has attracted more and more attention.In the grim situation of the global construction waste accumulation and resource scarcity,combined with the advantages of natural fibre,flax fibre reinforced polymer(FFRP)is applied to the confinement of recycled aggregate concrete with partially clay brick aggregate(RAC-CBA)to solve the defect of the recycled concrete.The following research are carried out:(1)The experimental study on tensile properties of FFRP.The tensile strength,elongation at break and stress-strain curves of FFRP are studied through the tensile test of FFRP sheet.(2)The experimental study on the axial compression performance of FFRP confined recycled concrete with brick aggregate.In this paper,the number of FFRP layers,the specimen size,the strength of core concrete are taken as variables.The axial compression tests of 36 recycled concrete cylinder specimens are carried out.(3)The analysis of stress and strain relationship of the FFRP confined recycled concrete with brick aggregate under axial load.The axial stress-axial strain relationship,axial strain-lateral strain relationship,middle strain-and end strain relationship are analyzed.(4)The analysis of the ultimate strength and ultimate strain model of FFRP confined recycled concrete with brick aggregate under axial load.This paper introduces and verify the classical models of strength and ultimate strain.Finally,the new model of strength and ultimate strain for FFRP confined recycled concrete with brick aggregate under axial load are proposed.(5)The study on the size effect of FFRP confined recycled concrete with brick aggregate.In this paper,the size effect is analysed and verified with the statistical methods including standard deviation analysis and single factor analysis of variance.The main innovation points of this paper are as follows:The use of flax fibre in the field of structural reinforcement provides a new way for the concrete reinforcement and the application of natural fibre in civil engineering.It also provides an effective way to deal with the disposal of construction waste and agricultural waste.