Application of High-Strength Concrete to Fill Tubular Steel Columns

When high-strength concretes are conveyed by pumping, the pumping pressure may increase and the flowability of high-fluidity concrete may be greatly decreased. This is a problem for construction of concrete-filled tubular steel columns. In this study, pumping tests and filling tests of steel tubular model columns with several kinds of high-fluidity concrete having a water/cement ratio of 30% were conducted. Silica fume results in better pumpability. The pressure loss reflects good correlation to the plastic viscosity of the concrete calculated from the time taken for it to discharge from an inverted slump cone. When the concretes used in the tests were pumped into tubular columns, the cavity area under the diaphragm plates was less than 10% and the core strength obtained at 91 days was over 80 N/sq mm. If the slump flow of concrete at the top of the column is more than 45 cm, it can be expected that the column will be filled well. The pressure of concrete at the bottom of the column is approximately 1.2 times the head pressure.