Abstract
This study examines the inelastic cyclic behaviour of square steel tubes infilled with rubberised alkali-activated concrete, incorporating slag-based binders and solid anhydrous sodium metasilicate activator. The rubber content, as a replacement for natural aggregates, is varied up to a high replacement ratio of 60%. Specimens are tested under lateral cyclic loading with a co-existing axial load of 0 and 20% of the cross-sectional axial capacity. The tests include 6 concrete-filled steel specimens and 2 hollow steel specimens for comparison. The experimental results and complementary material assessments are discussed in terms of the overall lateral cyclic behaviour and the key response parameters. The results indicate a reduction in stiffness, capacity, and ductility in proportion to the rubber content as well as the increase in axial load. The failure mechanisms of the composite specimens, including those with higher rubber content, are comparable. All concrete filled specimens show higher stiffness and capacity, and significantly improved ductility when compared to the hollow steel specimens. It is shown that the expressions given in Eurocode 4 for members subjected to combined bending and axial loading lead to conservative estimates of cross-section capacity.