The use of deicing salts or the existence of a marine environment presents a potential problem of chloride-induced corrosion of prestressing steel embedded in concrete bridge members---a problem that could ultimately lead to major structural damage. This potential problem is of particular concern in segmental bridges where the prestressing steel is located in close proximity to the deck or other exposed surface.
Good quality construction minimizes the potential corrosion of prestressing steel. Unfortunately, this is not always the case under actual field conditions and construction practices. Low permeable membranes and overlays, concrete sealers, and various methods of decreasing permeability of concrete are being used, but confidence in the long-term protection of prestressing steel is lacking. Therefore, more positive steps were needed to instill confidence in the use of prestressing steel in a chloride-potential environment.
Accordingly, techniques and materials to provide enhanced corrosion protection for prestressing steel and its associated metallic hardware in pretensioned and post-tensioned concrete bridges were reviewed. In addition, a year-long, accelerated corrosion test program on epoxy-coated strand, polyethylene duct, epoxy-coated steel duct, epoxy-coated anchorage hardware, grouts modified with silica fume and with calcium nitrate, and heat-shrink tubing for sealing post-tensioning duct joints, together with traditional materials was undertaken on pretensioned and post-tensioned members.
The research project is complete, and the principal findings have been published in NCHRP Report 313, "Corrosion Protection of Prestressing Systems in Concrete Bridges." Further detail was provided in an agency report entitled Supplement to NCHRP Report 313, "Corrosion Protection of Prestressing Systems in Concrete Bridges, Appendices A,B,C,D,E,F." These appendices provided additional information on the literature search and the conduct of the various experiments. The supplemental report was distributed to NCHRP sponsors only.
