Effects of Rust and Scale of Reinforcing Bars on the Bond Performance of Reinforcement Concrete

Abstract

To investigate the effect of reinforcement corrosion on the bond properties between concrete and reinforcing steel bar, pullout tests were conducted on a total of 20 specimens using corroded reinforcement bars embedded in concrete specimens. No. 3 (9.5-mm diameter) and No. 6 (19-mm diameter) bars corroded by an accelerated corrosion method were selected for testing. Two groups of corrosion specimens were prepared: one was whole-surface corroded (100%), and the other was partial-surface corroded with 40, 60, and 100% corrosion. Each group of specimens included four levels of corrosion: 3, 5, 10, and 15%. Results indicate that the tensile strength of steel bar decreases with the increase of corrosion level. Corrosion levels less than 3% present a minor tensile-strength reduction of approximately 3%, whereas the tensile strength may decrease to 75–90% when the corrosion level increases more than 10%. The critical bond strength and ultimate bond strength of corroded bars may increase slightly with corrosion level less than 3%, but tend to decrease as the corrosion level exceeds 3% and, likewise, to decrease with increasing corroded-surface percentage of steel bar. The range of partial-surface corrosion shows no significant effect on yield strength and ultimate strength of the steel bar. However, the critical bond strength and ultimate bond strength in a reinforcing steel bar decrease with the percentage of corroded surface for various corrosion levels when the corroded area increases from 40–100%.