Confined Expansion and Bond Property of Micro-Expansive Concrete- Filled Steel Tube Columns

The shrinkage/expansion behavior and bond carrying capacities were investigated through 4 micro-expensive concrete-filled steel tube(MCFST) and 3 conventional concrete-filled steel tube(CFST) short columns. The results show that the temperature field in MCFST is similar to that of ordinary concrete members. Concrete core has obvious effect on shrinkage-compensating with the addition of swelling agent. Pre-stress is produced in the core concrete when it is confined by the steel tube. Both water cement ratio and expansive agent have obvious influence on expansive behaviors of MCFST. The tests also indicate that the pre-stress in core concrete can improve bond strength of core concrete and steel tube of MCFST columns and proposed a new method to improve the interface bond strength of composite structures.