Interfacial Parameters for Bridge Connections at High-Strength Concrete–Ultrahigh-Performance Concrete Interface

Abstract

There has been a rapid increase in the use of ultrahigh-performance concrete (UHPC) in bridge connections and in bridge rehabilitation. When using UHPC in bridge construction, one common recommendation is that UHPC reach a compressive strength of at least 97 MPa before allowing traffic loads. However, bridges are subject to other loads prior to being open to traffic, such as load due to construction equipment, shrinkage, and temperature. The interface bond strength and interfacial parameters, such as adhesion/cohesion and the shear friction coefficients at early ages, are important in determining the ability of connections to resist these types of loads early on after casting. In this study, the interfacial bond strength between high-strength concrete (HSC) and UHPC was determined using pull-off, bi-shear, and slant-shear test methods at different ages. These test methods provide values of bond strength for different stress scenarios at interfaces, and the resulting values of bond strength vary by the test used. The adhesion/cohesion coefficients were calculated using experimental data, and the mean values were found to be in the range of 1.9–3.6 MPa and 3.2–6.5 MPa under tension and shear, respectively. The friction coefficients were found to be in the range of 1.37–1.52 due to tension and 1.07–1.37 due to shear. This research found that the adhesion/cohesion and friction coefficients are much higher than the values reported in AASHTO for initially roughened surfaces.