Mechanical Behavior of Reinforced Concrete Beams externally Strengthened with Carbon Fiber Sheets

Externally bonding carbon fiber reinforced polymer sheets with an epoxy resin is an effective technique for strengthening and repairing reinforced concrete beams under flexural loads. In this study, a total of seven reinforced concrete beams was tested and analyzed: two control beam and fourteen beams reinforced with one to six layers of carbon fiber sheets bonded by an inorganic epoxy. All specimens were subjected to a four-point bending test under load control while load, deflection, mid-span strain and failure mode were recorded up to failure. It is found that the load carrying capacity increases with the number of layers of carbon fiber sheet. For one to four layers of carbon fiber polymer reinforcement, the beams failed by rupture of carbon fiber polymer, while beams with five to six layers of fiber reinforced polymer reinforcement failed by carbon fiber polymer delamination. The results of the experimental clearly indicate that significant strengthening of reinforced concrete beams can be realized by bonding small amount carbon fiber reinforced polymer to the beams. The ductility of the carbon fiber polymer strengthened beams is greatly reduced compared to the control beam.