Bonding Steel Reinforced Concrete with Composites

THERE ARE MANY existing concrete structures in need of repair or poststrengthening, because of diverse reasons, such as overloading, cracks caused by temperature restraint, accidental damage, degradation over the servicing time, etc.... Methods of concrete repair involve the injection of cracks with epoxy resin or mortar [1-3], the bonding of steel [4-6] and fiber composite [7,8] plates to the tension section, etc. . . . Each of these methods has advantages and limitations. Fiber reinforced plastics (FRP) is characterized by its high ultimate strength, light weight, good corrosion resistance and versatile structure designability. Therefore, it is a potential material to be used where the repair is difficult to process [9]. So far, research on strengthening steel reinforced concrete (RC) beams through external bonding of FRP plates emphasized on the mechanics of short term behavior. The primary area of interest is the importance of strength increases provided by the bonded plates. This value depends largely on the reinforcement ratio in the concrete. With low steel reinforcement ratios, Ladner [10] found that the ultimate load doubled with a very thin carbon fiber reinforced plastics (CFRP) laminate sheet, while with a typical steel reinforcement, the value was about 22%. Ritchie et al. [11] bonded plates of glass, carbon and aramid fiber composite to the tension side of reinforced concrete beams using a two-part epoxy. They found increases in ultimate strength from 40 to fJ7 percent. Meanwhile theoretical analyses have also been developed [11-14]. Several aspects need to be considered in concrete repair, including material properties and structural design. For polymer materials, of which structural