Experimental Study Of Recycled Brick Aggregate Concrete-Filled Steel Tube Columns

In order to re-utilize the construction waste,it can be recycled into construction components that meet the requirements of constructional engineering.In the study of recycling of construction waste,the study on recycled concrete is relatively systematic;however,there is little study on the recycled brick aggregate concrete.The study on recycled brick aggregate concrete is still in the research stage of its mechanical properties,but little involved into its engineering application.In this paper,the basic mechanical properties of recycled brick aggregate concrete are studied,and the recycled brick aggregate concrete are used in concrete-filled steel tubular column.The feasibility of its application is discussed through experimental researches and computational analysis.The main contents and main conclusions are as follows:(1)C20 concrete was prepared with recycled brick aggregate and mixed recycled brick aggregate.The mixture proportion design,trial mixing and its mechanical properties were tested in accordance with the specifications.The final proportion of mixture was acquired thereafter and recycled brick aggregate concrete was prepared according to the test requirements.The best proportion of mixture is cement: sand : mixed recycled brick aggregate(recycled brick aggregate): water : slushing agent=1:2.705:2.865:0.45:0.007.The strength of mixed recycled brick aggregate than the strength of recycled brick aggregate increased by 14.1%.(2)Axial compression tests were done on short columns of steel tubular recycled brick aggregate concrete and that of mixed steel tubular recycled brick aggregate concrete with different wall thicknesses.The load-displacement curve and load-strain curve of the test pieces was recorded and analyzed.The results showed that:(1)the ultimate bearing capacity of short columns of mixed steel tubular recycled brick aggregate concrete was higher than that of the short columns of steel tubular recycled brick aggregate concrete.When the wall thickness from 1.8mm to 4mm,section steel content of increased by 2.62%,the ultimate bearing capacity of short columns of steel tubular recycled brick aggregate concrete and that of mixed steel tubular recycled brick aggregate concrete increased by 44.2% and 40.5%,respectively.When the wall thickness are 1.8mm and 4mm,the bearing capacity of columns of mixed steel tubular recycled brick aggregate concrete than the columns of steel tubular recycled brick aggregate concrete higher increased by 16.8% and 19.8%,respectively;(2)calculations were compared on the axially compressed short columns of steel tubular recycled brick aggregate concrete according to 9 relevant specifications both domestic and abroad.Among them,the calculation result according to DL/T 5085-1999 was the closest to the test result;however,the safety of the above was the lowest.(3)Eccentric compression tests were done on medium-long and long columns of steel tubular recycled brick aggregate concrete and that of mixed steel tubular recycled brickaggregate concrete with different wall thicknesses and slenderness.The load-displacement curve,load-strain curve and load-lateral deflection curve of the test pieces were recorded and analyzed.The results showed that:(1)the bearing capacity of eccentric compression of medium-long columns of steel tubular recycled brick aggregate concrete was lower than that of medium-long columns of mixed steel tubular recycled brick aggregate concrete.In terms of medium-long columns,through the comparison of the bearing capacity of the specimen,it can be found that when the wall thickness 1.8mm and 4mm,the bearing capacity of test specimens of mixed recycled brick aggregate concrete than the test specimens of recycled brick aggregate concrete lower by 25.7% and 18.2%,respectively;(2)calculations were compared on those eccentrically compressed medium-long and long columns of recycled brick aggregate concrete according to both domestic and abroad.Among them,the calculation result according to CECS 28:90 was the closest to the actual measurement,the factor of safety of it was the lowest.(3)As the slenderness increased,the deflection of the columns of steel tubular recycled brick aggregate concrete increased,and the load strength of the same decreased.When the length-diameter ratio from 5 to 10,a case study of the column of steel tubular recycled brick aggregate concrete,as the wall thicknesses are 1.8mm and 4mm,the lateral deflection of columns of steel tubular recycled brick aggregate concrete increased approximately by 9mm and 13 mm,respectively.And the bearing capacity of columns also respectively decreased by 17.6% and 11.2%.