Residual bond strength of highly corroded Reinforced Concrete

Corrosion of reinforcement due to chloride attacks in the marine environment is a natural phenomenon. Corrosion of reinforcement produces corrosion products of high volume, which deteriorates the structural integrity of reinforced concrete structure due to loss of bond, cracking and, spalling of the concrete. Existing literatures have documented tests investigating the bond behavior of uncorroded and corroded specimens, but there is a dearth of data pertaining to a more advanced stage (higher mass loss) of corrosion. In the current study, an accelerated corrosion test was conducted on cylindrical (lollipop) specimens, which involved utilizing an impressed current laboratory technique to induce three distinct levels of corrosion (10%, 20%, and 40% mass loss). Moreover, to assess bond strength, the pull-out tests were performed on both corroded and uncorroded specimens. The present study deals with the residual bond strength at three different corrosion levels, as a function of different parameters such as clear cover (CC), water-cement (w/c) ratio, and two different reinforcement diameters. Experimental data reveals that mass loss achieved is lesser than the target mass loss for all specimens. It is observed that at higher corrosion levels, where the mass loss exceeds 10% or cracks appear on the surface of the reinforced structure, both an increase in mass loss and a decrease in residual bond strength are consistently observed. These effects remain consistent regardless of whether the parameters such as bar diameter, w/c ratio, and clear cover are increased or decreased. The statistical analysis was performed on the experimental data to develop predictive models for estimating the residual bond strength and mass loss. For higher mass loss of 30-35%, the corresponding bond strength for all the specimens falls within the range of 4-6 MPa.