Abstract:To study the interfacial bonding properties of UHPC-CA steel pipe, the effects of internal curing technology and expansive agent on failure mode, load-slip curve and interfacial bonding properties are explored. The internal curing technology and the type of expansion agent are used as the experimental parameters to carry out the mix proportion optimization design and analyze its early expansion effect, and the optimal mix proportion (IC-CaO) and the conventional ratio (RE) are selected for the interfacial bonding performance test. The results show that the single internal curing technology and expansive agent can alleviate the early shrinkage of UHPC-CA, and the synergistic effect of the two can further improve its shrinkage performance, in which the internal curing technology combined with calcium oxide expansive agent (IC-CaO) can improve the early expansion effect most significantly. The failure mode of interfacial bonding performance test is the debonding at the junction of core concrete and steel pipe, but some concrete is attached to the inner wall of steel pipe in IC-CaO group. The average interfacial bonding strengths of RE group and IC-CaO group are 2.13 MPa and 2.91 MPa respectively in the tests, which shows that the interfacial bonding strength between UHPC-CA and steel pipe can be enhanced by the synergistic effect of internal curing technology and calcium oxide-based expansive agent.
