Modeling the Bond Stress at Steel-Concrete Interface for Uncorroded and Corroded Reinforcing Steel

Corrosion of reinforcing steel causes cracking and spalling of concrete structures, reduces the effective cross-sectional area of the reinforcing steel and the concrete simultaneously decreases the bond strength at the steel-concrete interface. The detrimental effect of corrosion on the service life of reinforced concrete structures highlights the need for modeling of bond strength between the corroded steel and the concrete. This research presents a nonlinear finite element model for the bond stress at the steel-concrete interface for both uncorroded and corroded reinforcing steel. The nonlinear finite element program ABAQUS is used for this purpose. The expanded volume of corroded product of reinforcing steel produces radial and hoop stresses which cause longitudinal cracks in the concrete. The increased longitudinal crack width, the loss of effective cross-sectional area of the steel and the concrete is also reduced due to the lubricating effect of flaky corroded layer. This research models the loss of contact pressure and the decrease of friction coefficient with the mass loss of the reinforcing steel. The model analyzes the pullout tests of Amleh (2002) and a good agreement is noted between the analytical and the experimental results. Both in FE analysis and experimental results, the loss of bond capacity is almost linear with mass loss of rebar. FE analysis and experiemental result show that, up to 5% mass loss, the bond capacity loss is moderate, at 10 to 15% mass loss, significant amount of bond capacity is lost and at about 20% mass almost all bond capacity is lost. The model is also validated by analyzing the pullout tests performed by Cabrera and Ghoddoussis (1992) and those by Al-Sulaimani et al.(1990).