Experimental Study on the Behaviour of CFST Columns with Steel Slag Concrete Under Axial Compression

Steel slag, a waste by-product in the steel industry, is now becoming increasing popular to replace natural coarse and/or fine aggregates in making concrete, which offers a sustainable solution in relieving the environmental problems due to huge depletion of natural aggregates and disposal of abundant slag. Extensive research studies revealed that steel slag concrete had superior strength and stiffness. However, the unique chemical composition of steel slag may cause unsoundness problem in the concrete, which scared the engineers in using it. To solve the problem, steel slag concrete-filled-steel-tube (SSCFST) column was proposed. By confining the steel slag concrete with steel tube, the concrete's expansion would activate larger confining stress and thus enhancing the overall behaviour of the column. A total of 6 SSCFST column specimens were fabricated and tested under uni-axial compression. The major testing parameters were the steel tube diameter to thickness ratio, the steel slag coarse/fine aggregate replacement ratio. Results revealed that by replacing natural coarse/fine aggregate with steel slag coarse/fine aggregate, the flowability of concrete reduced since steel slag was more angular and had higher water absorption and porosity. Besides, the compressive strength increased due to the cementitious property of steel slag. By filling the steel slag concrete into steel tube, the SSCFST column showed superior strength, stiffness and ductility owing to the composite action. The axial load was enhanced by 17% to 24% compared with the squash load (steel yield load plus concrete crushing load). With steel slag aggregate, the axial load was larger than that with natural aggregate only.