Shear Behavior of Reinforced Concrete Walls Retrofitted with UHPFRC Jackets

Ultra-high performance fiber reinforced concrete (UHPFRC) possesses outstanding mechanical properties and high durability, and thus can provide effective retrofit solutions for concrete walls and wall-type bridge piers. This self-leveling material can be cast in thin layers around the pier to protect it from corrosive environment and to enhance its shear resistance. However, while this is a promising solution, research has focused mostly on the retrofit of slabs and beams. To address this gap in knowledge, this paper presents results from four large-scale tests of shear-critical concrete walls with and without UHPFRC jackets. The test variables are the thickness of the jacket, the preparation of the concrete surface, and the level of axial load. It is shown that water-jetting of the surface ensures an effective composite action of the concrete and UHPFRC, while a smooth surface results in early debonding. It is also demonstrated that, while the reference reinforced concrete specimen failed in brittle shear, water-jetted walls with 30 mm and 50 mm jackets reached their flexural capacity and exhibited enhanced crack control. In addition to test results, the study also proposes and validates a three-degree-of-freedom kinematic model to accurately describe the deformation patterns of UHPFRC-strengthened walls.