This paper investigates the effects of the expansive agent on recycled aggregate concrete filled steel tubular (RACFST) stub columns under axial compression.
The main experimental parameters include an expansive agent ratio and recycled aggregate replacement ratio. In the current experimental study, owing to the enhanced confinement, the RACFST columns with an expansive agent have higher strength, ultimate strain, and ductility than reference RACFST columns.
Meanwhile, the concrete compressive strength measured by cylinders or cubes is generally lower than that of the expansive concrete triaxially confined after casting inside the circular steel tube.
Thus, the strength of reference ordinary concrete is applied for a finite element model and simplified strength formulas.
Through typical numerical examples, it can be found owing to the improved confinement, the strengths of expansive concrete filled steel tubular (ECFST) columns are slightly higher than that of their reference CFST column.
Thus, the strength design method for normal CFST columns can also be used for ECFST columns with an enhanced safety reserve.
