Effect of the Concrete Strength on the Concrete-Steel Bond in Concrete Filled Steel Tubes

In this study, the concrete-steel bond strength of concrete filled cylindrical steel tubes has been experimentally investigated. 22 short, high strength and normal concrete filled circular steel tubes were tested. Push-out test was carried out as the common method to evaluate the bond carrying capacity. Four different concrete mixes were used in preparing the specimens. The steel tubes were welded type with the nominal inside diameters of 3, 4, 6 and 8 inches. According to the test results bond strength increases with reduction of the w/c ratio of concrete mixes. The high strength to normal concrete bond strength ratio increases with the diameter of steel tubes. The bond strength decreases for higher diameters in both normal and high strength concrete specimens.