Abstract
This study examines the response characteristics of steel tubes infilled with sustainable rubberised alkali-activated concrete (AAC) materials. Focus is given to evaluating salient parameters relevant for seismic design, including those related to stiffness, strength, and ductility. These key parameters are derived based on the results of experimental assessments on steel tubes infilled with AAC incorporating rubber particles from recycled waste tyres. The concrete is made up of a slag-based mix activated with solid anhydrous sodium metasilicate. The rubber content, as replacement of natural aggregates, is varied up to a high replacement ratio of 60% by volume. Specimens are tested under lateral cyclic loading with a co-existing axial load of up to 20% of the cross-sectional axial capacity. A description of the experimental program is provided and discussed. The results show that while high rubber replacement ratios result in significant losses in concrete strength, the corresponding reduction in member capacity of the concrete-filled tubes is not as pronounced due to the contribution of the steel tube. Specimens with concrete infill, including those with high rubber replacement ratio, exhibited better seismic performance than comparative hollow steel tubes tested for comparison purposes. The test results generally demonstrate the favourable inelastic lateral cyclic behaviour of the steel tubes infilled with rubberised AAC, whilst also offering sustainable utilization of infill materials. Finally, the adequacy of design guidelines for conventional composite sections available in Eurocode 4 are also assessed for such members.