Corrosion-Resistant Stainless Steel Strands for Prestressed Bridge Piles in Marine Atmospheric Environments

About the report:

This study demonstrated that Type 2205 stainless steel strand can be used as a replacement for conventional ASTM A416 steel strands where an increase in service life is required.  The benefit and practicality of using Type 2205 stainless steel strand in prestressed piles were determined from two tasks performed in this study. 

First, a corrosion assessment was performed on stranded cold worked AISI 1080 carbon steel (hereinafter “SCW1080steel”) (equivalent to conventional steel strands); cold worked austenitic stainless steel Type 201 modified (hereinafter “CW201 steel”); and stranded heavily cold worked Type 2205 duplex stainless steel (hereinafter “SCW2205steel”), a currently available duplex stainless steel strand product.   Second, the fabrication and placement of several prestressed piles reinforced with SCW2205 steel, which are now part of Virginia bridge structures, were observed. 

Laboratory corrosion testing under different exposure conditions was conducted on SCW1080 steel (as a baseline); CW201 steel (with some limited testing on non-cold worked Type 201 modified stainless steel to evaluate cold working effects); and SCW2205 steel.  The laboratory studies were augmented with four-point bend and U-bend tests of specimens exposed to field conditions for 295 days.  

This study showed that in pore solution (strands embedded in quality concrete with no chloride), in concrete exposed to artificial seawater (strands embedded in concrete with the chloride concentration slowly increasing in pore solution), and in direct contact with artificial seawater (concrete damaged and strand exposed to artificial seawater), the SCW2205 steel outperformed the other steels tested.  Based on the corrosion test results, it is expected that SCW2205 steel strand will provide a considerably more corrosion-resistant reinforcement option in prestressed concrete products as compared to conventional strand. 

Design, fabrication, and driving of concrete piles reinforced with SCW2205 steel strands and Type 304 stainless steel spirals were documented for three bridges; a fourth structure is currently under construction.  Selected mechanical properties and estimated baseline costs were also determined for conventional ASTM A416 steel strands, SCW2205 steel strands, and carbon fiber reinforced polymer strands to facilitate life cycle cost analysis by others.

Based on this study, the Virginia Department of Transportation can implement the use of a corrosion-resistant strand in bridge elements in competition with carbon fiber reinforced polymer where corrosion is a concern, such as concrete elements exposed to brackish water, saltwater, or deicing salts.  

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