Investigation on the Flexural Behavior of Corroded Concrete Beams Repaired by CFRP Sheet Under Different Corrosion Levels

The paper presents an investigation on the flexural behavior of corroded reinforced concrete (RC) beam strengthened with Carbon Fiber Reinforced Polymer (CFRP) sheets. Different levels of corrosion are considered as a new method for classifying the corrosion levels of the corroded RC members. Twenty RC beams with five corrosion levels were fabricated by accelerated corrosion equipment, and then the CFRP were used to strengthen these members, considering the effect of different CFRP layers and different strengthened schemes, finally the static flexural load test was carried out. The test results show that the bearing capacity of the CFRP strengthening corroded RC beams is effectively enhanced, the crack width is restrained, and the flexural stiffness is improved. The ultimate flexural capacity of the specimens strengthened by one layer of CFRP sheet raises by 30% to 50% than that of the unstrengthened ones, with the increase of the corrosion level, the enhancement decreased. With the increase of the number of CFRP layers, the bearing capacity increases, while the increasing ratio reduces with the increase in the number of layers. For specimens with obvious cracks, the effectiveness of the strengthening method by bonding CFRP after cutting or chiseling off concrete method (RM1 or RM2) is higher than the method of bonding CFRP directly (DM). It is suggested that the corroded RC members with Level A, B or C1 can be strengthened by DM, while the other level members should be strengthened by RM1 or RM2. The formulae in current design code are used to predict the flexural bearing capacity of the RC beam strengthened with CFRP and their results are compared with experimental ones. A revised formula that can give a better prediction for multi-layer CFRP strengthening members is also proposed.