Structural performance of geopolymer-concrete-filled steel tube members subjected to compression and bending

Materials research has shown geopolymer concrete has the potential to significantly improve the sustainability of concrete construction. In this study, the structural performance of geopolymer concrete-filled steel tube members to take advantage of the beneficial confinement from the outer steel tubes is investigated experimentally and numerically. Experiments on eleven geopolymer concrete-filled steel tube specimens with either square or circular sections subjected to compression, flexure or combined loading conditions are presented. The experimental results, including the ultimate strength, load-deformation responses and failure modes, are obtained and also used as the basis for the validation of a finite element model which is subsequently used to perform parametric studies on the structures with varying cross-sectional dimensions, steel yield strength and member slenderness ratios. The experimental and numerical results are also used to evaluate the applicability of existing design standards for geopolymer concrete-filled steel tube members under combined compression and bending. The evaluation shows that the design approaches developed for ordinary Portland concrete-filled steel tubes in existing standards provide conservative strength predictions for the structures with the geopolymer concrete infill and can therefore be directly applied for safe structural design.