Bond Behavior of Concrete-Filled Steel Tube with Molybdenum Tailing

To investigate the bond behavior of the concrete filled steel tubular (CFST) using the molybdenum tailing as the fine aggregate, 24 test specimens of the CFST are designed in consideration of molybdenum tailing replacement ratio, concrete strength, ratio of the filling height to the outer diameter and ratio of the outer diameter to the wall thickness. A series of push-out tests are conducted to analyze the working mechanism, failure mode, and bond stress-slip relation of the test specimens. The results show that the usage of the molybdenum tailing as the fine aggregate has no obvious effect on the working mechanism and failure mode of the CFST regardless of the test parameters, even though a slight difference is observed in the failure processes. The increase in the molybdenum tailing replacement ratio remarkably decreases the ultimate bond strength, but increase the ultimate failure slip of the test specimens whilst the ultimate failure slip shows no distinct change under the same ratio of the filling height to the outer diameter and ratio of the outer diameter to the wall thickness. The CFST test specimens with the molybdenum tailing shows slightly worse bond behavior than those without the molybdenum tailing. The proposed formula for the ultimate bond strength of the CFST with the molybdenum tailing fits well with the test results. Since, the limitations regarding the ultimate bond strengths of the CFST in the existing relevant specifications show the enough safety reserve, the proposed formula can be directly used for the design of the CFST with the molybdenum tailing.