Corrosion propagation of prestressing steel strands in concrete subject to chloride attack

A review of research literature suggests that steel corrosion in concrete can accelerate if the corroding steel is under high levels of stress but this important phenomenon has not been investigated thoroughly. Both laboratory tests and field surveys indicate that the effects of corrosion on structural behaviour in reinforced and prestressed concrete structures are different, with the latter having less concrete cracking but more serious structural collapses. The intention of this paper is to investigate the corrosion propagation of prestressing steel strands in chloride-laden environment. A long term experimental program is presented in which the corrosion of twelve prestressing steel strands embedded in concrete was examined. The effects of the level of stresses in the steel and type of steels on corrosion rate are studied. It is found that the corrosion rate of prestressing steel strands in concrete increases with the increase of the level of stresses applied and that the pitting corrosion is the main form of prestressing steel corrosion in chloride-laden environment. The paper concludes that the corrosion of prestressing steel in concrete structures poses higher risk to the structure than that of reinforcing steel in terms of structural collapse.

► Corrosion rate of all steel strands and bars decreases over time in a nonlinear manner in general.
► Corrosion rate increases with the increase of stress in prestressing steels in an approximate linear manner.
► There are fewer corrosion cells on the surface of prestressing strands than that of deformed bars.
► Corrosion rate as measured by polarization resistance technique may not represent the true corrosion state of prestressing steels in concrete.
► Higher chloride content in concrete leads to greater overall corrosion rate.