Influence of Heating and Cooling Temperature on the Performance of Tensile Interfacial Bond between High Strength Concrete and Ultra High Performance Concrete (UHPC)

Abstract

Ultra-high performance concrete (UHPC) is a cementitious material which has superior mechanical properties, ductility, and long-term durability. The exceptional performance and outstanding properties of UHPC makes it suitable as a grout material in connections between prefabricated bridge elements or an overlays for bridge rehabilitation. However, UHPC has high coefficient of thermal expansion (CTE) as compared to conventional or high strength concrete (HSC) due to its high cement content and the absence of the coarse aggregates. The difference in the CTEs between HSC, normally used in prefabricated bridge elements, and UHPC generates thermal stresses at the interface when subjected to heating and cooling temperature. The thermally induced stresses could lead to interfacial failure when the interface bond strength is exceeded or cause a reduction in the bond strength. In this study, the effect of heating and cooling temperature on the interface bond strength was investigated using a direct tension test. Composite specimens made of HSC and UHPC were subjected to heating and cooling temperature based on the AASHTO LRFD bridge design specifications and then tested under direct tension. The thermal strains generated under these conditions were also measured for both materials and then plotted against temperature. Composite specimens stored under room temperature conditions were also tested in the direct tension apparatus, and the results compared with those of composite specimens subjected to heating and cooling temperature. A bond versus slip relationship under room temperature that was investigated from the previous research was compared with relationship under temperature conditions. A reduction of 34% in the mean bond strength was observed when the composite specimens were subjected to heating and cooling temperature.