Rehabilitation of Reinforced Concrete Structures Using Shape Memory Alloys

The near-surface-mounted (NSM) strengthening method is a relatively new method for rehabilitation of reinforced concrete structures and can overcome some of the disadvantages of the other strengthening systems. In NSM method, longitudinal grooves are first cut into the concrete cover of an RC member, then reinforcing bars or strips, are inserted in these grooves and bonded with an epoxy paste or cementitious material. Although the NSM reinforcement can preclude delamination-type failure, one of the main factors that affect the efficiency of the NSM method is still the bond between the NSM reinforcement and the concrete. Shape memory alloys (SMA) are a class of metallic alloys that can remember their original shape upon being deformed. Besides their ability to recover large strains with minimal residual deformations, SMAs possess excellent corrosion resistance, good energy dissipation capacity, and high fatigue properties. This study investigates bond characteristics and load transfer mechanisms between NSM SMA reinforcement and concrete. A modified pullout test set-up that consists of a C-shaped concrete block, where the NSM reinforcement are placed at the center of gravity of the block, are used for experimental investigations. The effects of various parameters such as NSM reinforcement type, embedment length, type of epoxy on the bond behavior are studied. The slip of the SMA reinforcement relative to concrete is measured using DIC method at the loaded and free ends of the specimen and the bond-slip curves are developed.