Axial compressive performance of seawater sea sand rubberised concrete filled stainless steel tubes

This study presents an experimental investigation on the axial compressive performance of seawater sea sand rubberised concrete (SWSSRuC) filled circular stainless steel stub tubular columns. SWSSRuC reduces the reliance on traditionally used raw materials, namely river sand and freshwater, while also facilitating the recycling of discarded tyres. To mitigate the reduction in strength and stiffness of SWSSRuC, confinement through stainless steel tubes was employed. A total of twelve confined specimens were tested, considering the effects of varying concrete strength grades, rubber replacement levels, and diameter-to-thickness ratios. Their contributions to the failure modes, load-displacement behaviour, strain development, confinement mobilisation, initial axial stiffness, and ductility index were evaluated, providing new insights into the interaction between stainless steel tube and concrete core incorporating rubber aggregates. The results show that the degradation in the SWSSRuC’s mechanical properties was effectively restored, and the pairing of stainless steel tubes and SWSSRuC core enhances the post-peak performance, potentially rendering these composite columns as a viable solution for lightweight and sustainable marine infrastructure that requires superior ductility. Since existing design models in the literature could not accurately predict the axial capacity of tested specimens, a refined equation is proposed to estimate the peak load of stainless steel tubes infilled with various concrete types, based on a more extensive database.