Repair of corrosion-damaged columns with FRP wraps

Corrosion of reinforcement in bridge piers is encouraged by chloride contamination from exposure to marine environment and from deicing salts used in bridges during winter. Because corrosion products generally occupy greater volume than the original material, expansive forces are generated in concrete leading to spalling of the cover and further acceleration of the reinforcement disintegration. Jacketing of such structures by fiber-reinforced composite sheets is an effective remedy, not only as a means of slowing down the rate of the reaction, but also by confining the concrete core thereby imparting to it ductility and strength. This paper presents results of an experimental parametric study of this method as a repair alternative for corroded structures. Several small-size concrete columns with various reinforcement configurations were subjected to accelerated corrosion conditions in the laboratory. After a target level of steel loss was attained the columns were repaired using a variety of repair alternatives. Most of the repair schemes considered included jacketing the damaged specimens with glass-fiber wraps, in combination with grouting the voids between the jacket and the original lateral surface of the specimen with either conventional or expansive grouts. To protect the glass fiber material from exposure to alkali activity of the fresh grout, and to reduce the supply of oxygen and water to the mechanism of corrosion, different types of diffusion barriers were considered in the study. The efficacy of each repair system was evaluated by (1) assessing the postrepair corrosion resistance of the specimens under repeated exposure to accelerated conditions; and (2) the mechanical strength and ductility enhancement under concentric compression loading.