| Corrosion of reinforcement is one of the major contributing factors to the deterioration of concrete structures. The contribution of reinforcement to the structure is reduced due to the loss of cross section and deterioration of bond between the reinforcement and concrete. Bond strength loss, which is much more critical than the loss of cross section, was evaluated under both confined and unconfined conditions. High strength carbon composite, which is a popular repair material, was used to provide the confinement.; For unconfined samples, the major variables were corrosion levels and bar diameters. The corrosion levels varied from 0% to 12.25% diameter loss and the bar diameters were 10, 13, 16, 19, and 25 mm. Bond specimen geometry was chosen so as to induce tensile strains in concrete surrounding the reinforcement. Electrolyte corrosion technique was used to induce accelerated corrosion. Pullout tests were conducted to obtain the complete bond slip behavior. Bond strength and slip were evaluated and analyzed at various corrosion levels.; One and two layers of carbon fabric were used to provide confinement. For this set of specimens, corrosion levels varied from 0.39% to 6.36% diameter loss. The confining layers were placed after corrosion has occurred to simulate repair process. During the pullout tests, strains in the carbon composite at various locations were measured in addition to the completebond slip behavior.; Analytical procedures were developed using the experimental results of this investigation to predict the behavior of slabs and beams tested by other investigators. The slabs and beams had unconfined and confined reinforcement.; The results confirmed that the loss of bond strength for unconfined reinforcement is much more critical than cross section loss. Two percent diameter loss could lead to 80% bond reduction. Loss of bond in larger bar sizes is more evident than in smaller bar sizes. Confinement provides excellent means to counteract the bond loss. Even at a maximum diameter loss of 6%, the bond strength could be maintained at 100% level of uncorroded unconfined bars. |
