Anchorage Capacity of Corroded Reinforcement

Report, 2010

There is a growing need for reliable methods of assessing the load-carrying capacity and remaining service life of corroded structures. Previous research has been mainly concerned with lower corrosion levels leading to cover cracking. Moreover, the main focus of the available knowledge concerns the corrosion of the main reinforcement; while the corrosion of the stirrups is often overlooked. Therefore, these two uncertainties ; i.e. high amount of corrosion leading to extensive cover cracking and spalling and the effect of corroding stirrups, were investigated in an experimental program. Pull-out tests were carried out on eccentrically reinforced specimens with long embedment length to study the anchorage capacity of a corroded bar. The influences of the location of the anchored bar, i.e. middle or corner placement; the presence or absence of transverse reinforcement; the corrosion level of longitudinal reinforcement and the corrosion of transverse reinforcement were studied. The specimens were of three types in relation to the reinforcement arrangement and corrosion: specimens without stirrups, where the main bars were corroded (type A); specimens with stirrups where the main bars were corroded and the stirrups were protected by insulating tape (type B); and specimens with stirrups where the main bars and stirrups were corroded (type C). All of the specimens were subjected to accelerated corrosion, with an average current density of 100 µA/cm2, for three time spans that caused a rebar weight loss up to approximately 20% in the main bars and 35% in the stirrups. All of the specimens showed longitudinal cracks along the main bars for relatively low corrosion levels. The corrosion level at first cracking was about 0.6% 1.0% corrosion weight loss; the cracks widened with increased corrosion levels. Crack patterns formed depended on the presence or absence of stirrups and whether the stirrups were corroded. The crack patterns showed differences between specimens with or without stirrups and when stirrups are corroding or not. The tests showed an important effect of the cover cracking in terms of loss of confinement. They also indicated that the bond behaviour and the failure were strongly governed by the position of the anchored bar, i.e. corner or middle positions, and the level of the corrosion attack. Stirrups played an important role after cover cracking, as they then became the primary source of confinement. The knowledge gained in this study contributes to better understanding of the effects of deterioration on structures.