Experiment Study Of Axial Compression Behavior Ofrecycled Concrete Filled Double-skin Steel Tube After Sulfate Corrosion

Due to the complexity of topography and landform,the durability of buildings in complex environment has been widely concerned.However,the decreasing building sources make the appearance and promotion of recycled concrete.As a kind of building material,recycled concrete has low strength and poor durability,which greatly limits its application in high-rise buildings and special projects.The paper studies the different performance of concrete with different recycled aggregate rate(0,50%and100%)and recycled concrete with 50% recycled aggregate of different mixing amount of basalt fiber(2,4,5,6kg/m3)resistance to sulfate corrosion.It gets the compressive strength,elastic modulus and peak strain curves of concrete after different times of sulfate attack and dry-wet cycles,analyses load-deformation entire process curves of concrete and two types of failure mode of recycled concrete,presents analysis of compression failure mechanism of recycled concrete,applies the coefficient K of combined effect to characterize the superimposed effect of mixing basalt fiber and sulfate erosion.The results show that: the recycled aggregate and basalt fiber both weaken concrete resistance to sulfate corrosion,but have little effect on elastic modulus of concrete(under 4.7%);with the increase of mixing amount of basalt fiber in recycled concrete,its peak strain increases;load-deformation curves also reflect these properties;the destruction forms of cubic and cylindrical specimen are different,corrosion of internal interface transition during the experiment is one of the main causes of concrete destruction form;mixing basalt fiber can strengthen the resistance to sulfate corrosion of the recycled concrete by calculating the K value.Concrete filled double skin steel tubular cube is a better component form based on concrete filled steel tubular cube.It has advantages of low weight,good mechanical properties,simple construction and so on.As a new component form,it has been widely used.But its durability has not been studied now.In this paper,the resistance to sulfate erosion of concrete filled double skin steel tubular cube is studied.It analysis the influence of slenderness ratio(4/4.5/5),section form(circle in square and square in square),sulfate concentration(5% and 10%)and erosion times(30 times and 60 times),compares the change of mass,compressive properties,peak strain and load-displacement curves of the cubes.The result shows that: when slenderness <5,it has little effect on the properties of concrete filled double skin steel tubular cube;the mechanical properties of circle section are better than those of square section;the speed of erosion speed up with time;the concentration can speed the erosion speed quicker than time when the concentration is low;however the resistance to sulfate erosion of concrete filled double skin steel tubular cube is better than steel or concrete due to the steel protect concrete from erosion.Use of recycled concrete would not influence the performance of concrete filled double skin steel tubular cube,reduce the price and be more environmental at the same time.