Effect of Cyclic Temperature and Fatigue Load on the Performance of Bond Strength at High-Strength Concrete–UHPC Interface

Abstract

One of the most important components of box beam bridges is the shear key that connects the box beams together. The shear keys in box beam bridges often fail at the interface. In recent years, ultrahigh-performance concrete (UHPC) has been successfully used to cast these shear keys. The current study investigates the effect of temperature cycles on bond performance between a high-strength concrete (HSC) box beam and UHPC shear key. The interfacial bond performance was evaluated by subjecting specimens to 60, 120, and 180 freeze-thaw (FT) cycles representing 1, 2, and 3 years of environmental exposure. Some direct tension specimens that were subjected to 180 FT cycles were additionally subjected to 1-Hz frequency fatigue cycles with stress reversals. Using the direct tension, pull-off, slant shear, and bishear assessment methods, the test results have demonstrated that the number of FT cycles did not affect bond performance in terms of strength and failure modes. The test results also showed that standard specifications underestimate the cohesion and friction coefficients evaluated using Mohr-Coulomb’s and Carol’s approaches for concrete placed against intentionally roughened surfaces. Furthermore, it was found that fatigue loading with stress reversals did not diminish the direct tensile bond strength of the specimens.