Experimental Ressearch On Recycled Pebble Concrete Filled Circular Steel Tubular Stub Columns Subjected To Axial Compressive Loading

At present,the gravel crushed from waste concrete is mainly used as recycled coarse aggregate(RCA)to reproduce recycled aggregate concrete(RAC)in construction-at home and abroad,while the-renewable pebble is rarely employed as coarse aggregate and there hardly exist relevant regulations concerning recycled pebble or RAC made from this kind of RCA.Because of the obvious differences between recycled pebble and recycled gravel in external shape,the mechinal properities of RAC made by hese two RCA may differ a lot and it is unreasonalbe to directly apply the research conclusions of recycled gravel concrete,which makes it useful to test the basic performace of RAC made of recycled pebble.The combination of steel tube and inner RAC can make up the drawbacks of the RAC and make it more applicable in engineering construction.In view of what has been discussed above,this research has been conducted to investiagte the basic performance of recycled pebble concrete and the recycled pebble concrete filled steel tubes:(1)The mechanical properties of RAC made of recycled pebble including the compressive strength and elastic modulus were tested and these results were co MPared with normal aggregate concrete as well as RAC made of recycled gravel.The main paramaters considered in the test procedure are the replacement ratio of recycled pebble from 0% to 100% with the interval of 25% and the age of recycled pebble concrete including 7d,14 d,28d,56 d,90d and 180 d.The compressive strength of totally replaced RAC decreases 4.4% when co MPared to NAC at 28 days and this percentage is 22.8% for Yong's modulus.(2)The axial loading test was conducted on steel tube filled with RAC made of recycledpebble and the experiment phenomenon and failure mode were recorded.The bearing capacity,axial load-axial strain curve and axial load-horizontal strain curve as well as the elastic stifiness were analyzed.As for the RACFST columns,the bearing capacity drops 8.6%% with the replacement ratio increasing from 0% to 100%.(3)The striping analysis method is employed to analyze the stress state of outer steel tube to acquire its vertical stress-vertical strain and horizonal stress-vertical strain relations.At the same timen,the vertical stress-average vertical strain relations of core concrete and,the confining stress between steel tubes and concrete versus average vertical strain relations are also obtained.