Bond behaviour in Self Compacting Concrete Filled Tubes

The paper investigates the bond behavior on slices obtained by circular steel columns (prior to casting) of 131mm internal diameter, 4mm thickness, 50mm height with an embedded length of 40mm. Scope of the test is to push-out the concrete core from the steel ring. By imposing a global displacement to the concrete core and measuring the reaction force and the relative displacement between the two materials it is possible to obtain a bond stress-slip law under the assumption of a constant bond stress acting along the interface, Three different concretes for structural applications as composite elements are investigated, each of them designed for a 28-day cylindrical compressive strength of 50 MPa: (i) a Normal Vibrated Concrete, (ii) a SelfCompacting Concrete, (iii) an expansive Self-Compacting Concrete (with the goal of an increase in bond strength as a consequence of the expansion).