Understandings on the Performance of Concrete-Filled Steel Tube with Different Kinds of Concrete Infill

In recent years, concrete-filled steel tube (CFST) has gained attention in the construction sectors due to its unique static and earthquake resistant properties. The steel-concrete composite member is formed by filling the concrete inside the hollow steel tube of various shapes. The experimental and numerical investigations were carried out for CFST members filled with different types of concrete of the same grade. The types of concrete used for this study are conventional concrete, steel fiber-reinforced concrete, geopolymer concrete, and expansive concrete, respectively. The concretes were cast in the form of cubes followed by curing underwater and self-curing conditions. The specimens cured for 7 and 28 days of age were subjected to axial compressive strength testing. The effect of curing conditions on the strength of concrete was evaluated by comparing the obtained results. Self-curing, the only possible way of curing infilled concrete in the case of CFST columns, was found to have no influence on the strength of concrete, and the same curing method was adopted for the CFST columns tested in this study. A total of 24 CFST specimens were cast by different types of concrete infill, and their load carrying capacity under axial compression and their bond strength were determined through experimental investigations. The characteristic strengths measured for the CFST columns with different types of concrete infill were compared, and the results are presented. The analytical investigations were carried out by using Eurocode-4 to predict the load-bearing capacity of CFST columns under axial compression. Finally, the load carrying capacities of CFST columns under axial compression obtained through experimental and simulation studies were compared and the results are presented.

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