Experimental study on bond strength of interface between steel fiber reinforced reactive powder concrete and steel tube

In order to investigate the bond strength of the interface between steel tube and infilled steel fiber reinforced reactive powder concrete (RPC), a series of pushout tests with a total of 27 specimens of RPC-filled steel tube with different thickness of steel tube, steel fiber volume content and curing temperature were conducted. It is found from the test that curves of load-slip of RPC-filled steel tube are a little different from those of normal concrete-filled steel tube, that is, the former have no noticeable peak point and possess secondary ascending segment. Parameters including curing temperature, thickness of steel tube and steel fiber volume content play different roles on influencing both initial bond strength and ultimate bond strength. As the thickness of tube wall is increased from 1.41mm to 3.45mm, the initial and ultimate bond strength are increased by 68% and 64%, respectively. As the curing temperature is increased from 20℃ to 90℃, the initial and ultimate bond strength are increased by 30% and 11%, respectively. The influence on bond strength by steel fiber changes at different volume contents. The initial and ultimate bond strength are decreased by 2% and 11% along with the increase of the volume content from 0% to 1%, but increased by 54% and 21% along with the increase of the volume content from 1% to 3%.