Bond Behavior of Corroded Steel Reinforcement in Concrete Wrapped with Carbon Fiber Reinforced Polymer Sheets

This paper examines the ability of carbon fiber reinforced polymer (CFRP) wrapping to enhance the bond of corroded reinforcing steel bars in concrete. Thirty-two bond pullout specimens were considered. Test variables included the clear concrete cover (15, 30, and 60 mm or 0.6, 1.2, and 2.4 in.), degree of corrosion (0, 1, 5, 7, and 10% mass loss), and presence or absence of transverse CFRP wrapping. The specimens consisted of a concrete prism measuring $150\times 150\times 200\mathrm{mm}$ $(6\times 6\times 8\mathrm{in}\text{.})$ with a No. 10 M reinforcing bar placed in the corner of the prism. The specimens were constructed with 3% ${\mathrm{Cl}}^{-}$ by weight of cement premixed in the concrete to depassify the tensile reinforcing steel. The specimens were placed in a constant high-humidity environment, and corrosion was induced by means of an impressed current. Following corrosion, the specimens were tested by bar pullout to determine the bond strength versus slip of the reinforcing bars. The bond strength of the reinforcing bars in the concrete prisms increased at a small level of corrosion, but decreased as the degree of corrosion increased. The failure mode typically was bond splitting in unwrapped specimens. Strengthened specimens exhibited an increased bond strength and failure by bar pullout due to the confining effects of the CFRP strengthening.