CORROSION OF POST-TENSIONED TENDONS IN FLORIDA BRIDGES

Severe corrosion distress and failures in post-tensioned tendons has been found in two major bridges in the State of Florida. Corrosion distress and complete tendon failure has been identified in horizontally oriented tendons that support pre-cast bridge superstructure box segments. In virtually all instances, the observed corrosion has been associated with the presence of grout voids and visual evidence of grout bleed water having been present for indeterminate periods of time. With few exceptions, corrosion induced strand failures have occurred in the immediate vicinity of the anchorage. The anchorage systems in both bridges utilize a proprietary multi-plane anchorage (housing) comprised of ductile cast iron and forged steel wedge plate. The presence of these metals coupled with high strength strands gives rise to concerns relative to galvanic corrosion thus prompting this preliminary investigation focusing on dissimilar metals corrosion. The investigation involves laboratory tests that examine the corrosion aspects of grout bleed water and re-charge water in contact with dissimilar metals comprising the tendon and anchorage system. The preliminary results indicate that the high strength post-tensioned strands are mostly anodic to the anchorage system when exposed to either grout bleed water or recharge water such as that which may be experienced through leakage. The preliminary findings of the investigation are presented along with the implications on existing structures and on future design and materials selection for post-tensioning systems