| Faced with the increasing construction waste and the shortage of natural resources such as the natural river sand,recycled aggregate(termed as RAC)concrete is undoubtedly one of the important ways to solve the above problems.Recycled concrete is a kind of concrete which is made up of waste concrete block or waste brick by classification,crushing and sieving into recycled aggregate,partly or completely replacing natural aggregate such as sand and stone,and then adding cement,water and so on.However,it is found that recycled concrete has some disadvantages,such as low strength and poor ductility,compared with ordinary concrete.At present,recycled concrete aggregate is mainly abandoned concrete aggregate,but demolition of old building will produce a large number of brick aggregate,so it is necessary to study brick aggregate.The compressive strength and ductility of recycled concrete can be effectively improved by external constraints.Using stirrups to restrain recycled concrete,it has good mechanical performance,and it is more economical than steel tube confined recycled concrete(termed as STCRC).It has the advantages of convenient construction on the spot,not easy to occur rust,easy to maintain and so on.Compared with fibre reinforced polymer(termed as FRP)confined recycled concrete,the stirrups confined concrete is more economical and the durability is more easily guaranteed.Compared with common stirrups,spiral stirrups(termed as SS)provide more uniform binding force on core concrete,so the effect of constraint is more obvious.In this paper,spiral stirrups are used to restrain recycled aggregate concrete with clay brick aggregate(termed as RAC-CBA),and longitudinal reinforcement is used to form a reinforced recycled concrete column to study the axial compressive behavior of recycled aggregate concrete with clay brick aggregate confined by spiral stirrups.The main contents of this paper are as follows:(1)The Study on properties and mix ratio of recycled concrete with brick aggregate.At first,the physical properties of recycled aggregate and natural aggregate are tested,and the mixture ratio of different water-cement ratio is tested to determine the mix ratio of strength of two kinds of recycled concrete.(2)The experimental study on axial compressive behavior of cylindrical specimens containing recycled concrete with brick aggregate confined by spiral stirrups.In this paper,28 specimens of recycled concrete with brick aggregate confined by spiral stirrups are tested under axial compression.The experimental variables are the strength of recycled concrete,the ratio of longitudinal reinforcement and the spacing of spiral stirrups.(3)The failure patterns and stress-strain curves of recycled concrete with brick aggregate confined by spiral stirrups are analyzed,and the factors affecting the bearing capacity and ductility of recycled concrete with brick aggregate confined by spiral stirrups are analyzed.(4)The study on the peak stress,peak strain and ultimate strain model of recycled concrete with brick aggregate confined by spiral stirrups.By comparing the error between the experimental value and the calculated value of the classical model,using the expression form of the classical model and regression fitting of the test results.The peak stress,peak strain and limit strain models of the recycled concrete with brick aggregate confined by spiral stirrups is put forward.(5)The study on constitutive relation model of recycled concrete with brick aggregate confined by spiral stirrups.This paper first introduces the classical constitutive relation model of stirrups confined concrete at home and abroad.Through the comparative analysis of the stress-strain full curve and the classical constitutive model curve,the suitable expression form of the classical constitutive model is adopted,and the stress-strain complete curve is compared with the classical constitutive model curve.Based on the self-test data,a constitutive relation model of recycled concrete with brick aggregate confined by spiral stirrups is proposed. |
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