Bond Characteristic Research For Corroded Reinforced Concrete Based On Experiment

Concrete and the steel bars working together well depend on the bond stressbetween each other; at the same time, the bonding problem is a focus for the concretetheory. However, as the defect of concrete durability appears in some projects, thedurability about bond is concerned as well. Many studies show that steel-bar corrosionis one of the most important factors affecting concrete durability and deteriorating thebond characteristic as well. However, it’s necessary to continue making more studies onthis topic because of its complex mechanism, numerous influencing factors anduncompleted theoretical system.By using the quick steel-bar corrosion principle, this paper first obtains two groupscorroded specimens with different diameters (B12andB18) and different corrosionpercentage. Then the distribution and width of the corrosion expansive cracks isinspected by using the non-destructive Industrial Computed Tomography (ICT).At last,bond-slip characteristic is investigated through pullout experiment.Quick steel-bar corrosion test proves that as the corrosion product accumulategradually, the inside of concrete differ as well—a low corrosion percentage with no rust,but even cracked completely if corroded more seriously.According to the ICT scanning, the width of cracks becomes narrower from theinside to the outside on the condition that the cracks have not penetrated the specimensurface, otherwise, the width become wider.Through pullout experiment, bond-slip characteristic is investigated. It induces thatall the corroded specimens fail in a split way. However, slight difference remain existbetween the specimens of B12group, when the corrosion rate is lower, the specimensare spited suddenly and no descent stage is generated for the load-slip curves; if the rateis higher, both ascent stage and descent stage can be found in load slip curve, and thesespecimens first crack near ultimate load point but still with load capacity till separatedinto several parts at last.Each of the ultimate load and free end slip load, has a similar relationship withcorrosion rate, while corrosion rate is lower than the demarcation point, they increasewith corrosion rate together, once the rate exceed it, they began to decrease. However,the specific demarcation point for the ultimate load and free end slip load is not thesame. At the same time, all the slippage for the corroded is smaller than the sound. Morover; the average bond slip curve is also fitted.By placing the strain gauge in the reinforced bars, the relationship between bondstress and slip at different position along the steel bars is inspected and aposition-function is proposed as well.By making a reference of the finished experiment data, a formula for calculatingthe ultimate bond stress which considered several factors is proposed.