Although expansive additives are frequently used in contemporary concrete-filled steel tubular (CFST) structures to improve the bond between concrete and steel tubes, little information is available regarding their influence on the mechanical characteristics of CFST columns. This reflects the pressing need to investigate the impacts of the pre-stressing achieved through the expansive additives, especially on the concrete confinement and axial load capacity of CFST. This paper thus discusses the results of concentric load tests carried out for 12 pre-stressing CFST columns to assess their axial load capacity and modes of failure. The main parameters investigated are the concrete compressive strength (40, 50 and 90 MPa) and the dosage of the expansive agent (0%, 6%, 12% and 24% by mass of cement). The results indicate that the axial load capacity is improved by increasing both the concrete compressive strength and the expansive additive dosage. The expansive additive has an important influence on the confinement effect of CFST. The paper presents new test results that contribute to fill a gap in the literature and provides insights into the behavior of concentrically loaded pre-stressing CFST columns.
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