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. 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 nitrite, and heat-shrink tubing for sealing post-tensioning duct joints, together with traditional materials was undertaken on pretensioned and post-tensioned members. Epoxy-coated strand, epoxy-coated anchorage hardware and epoxy-coated steel duct all were found to significantly enhance corrosion performance. The polyethylene duct provided excellent performance, particularly when used with the heat-shrink tubing to seal the duct joints. The use of newer corrosion-resistant duct materials and watertight duct joints was found to be essential since all three grout formulations were highly permeable to chloride at joints sealed with duct tape, or after the traditional steel ducts corroded. Bond tests indicated that polyethylene duct and epoxy-coated steel duct can provide structurally composite behavior between the concrete and grout. Friction and abrasion tests demonstrated that a high coefficient of friction and abrasion damage may result if epoxy-coated strand is used in corrugated metal duct with a small radius of curvature. Polyethylene duct, which provides a low coefficient of friction, may also be subject to abrasion damage under certain conditions. Future research based upon this extensive literature review and corrosion testing program is suggested.
Samenvatting