Behavior of expansive concrete-filled steel tubular columns under axial loadings

Concrete-filled steel tubes (CFSTs) have been introduced to expedite construction and increase the confinement of concrete by the steel tube. While changing the confinement level through the use of expansive additives (EAs) will have an impact on the performance of CFSTs, limited information is available on the behavior of expansive concrete-filled steel tubular (ECFST) columns. The objective of this study is thus twofold: (i) to experimentally assess the behavior of axially loaded ECFSTs, and (ii) to investigate the correlation between the test results and those obtained from prediction approaches. The experimental program of this study consists of testing four 1500 mm CFST/ECFST columns with 153.6 mm outer diameter and 3 mm thickness. The ECFST specimens are divided into two subgroups with 0% and 12% EA dosage and two concrete mixtures, 16 and 37 MPa. The results indicate that the latter is the most promising mixture since it results in a significant enhancement of 64% in the axial load capacity of ECFST columns compare with CFSTs. The study also recommends employing specific confined concrete models with the existing code prediction approaches to arrive at the best correlation with test results.