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South Dakota Department of Transportation
Project Synopsis
SD2000-04


Title: Stainless Steel Clad Rebar in Bridge Decks
Project Researcher: William Cross, SDSM&T
Project Manager: Dave Huft
Research Period: 3/7/2000 - 6/30/2002
Status:
Cost: $57,696.00

Problem Statement: The ongoing problem of corrosion of reinforcing steel in bridge decks has been addressed in South Dakota with increased concrete cover over reinforcement and the use of epoxy-coated rebars (ECR). To date, these measures appear to have worked well extending bridge deck life significantly. With the development of new materials and technologies, the potential for increasing deck life may be even greater. One of these new materials is proprietary stainless steel clad (SSC) reinforcement, which consists of mild steel clad with 316L stainless steel during fabrication. A tube of stainless steel is packed with chips of mild steel using a 400 ton ram and heated until the mild steel becomes molten and mixes with the stainless steel at the interface. The process results in a solid bar with a thin cladding of stainless steel. The stainless steel is much less susceptible to corrosion than black steel and may provide the means of preventing corrosion from deicing salts from occurring throughout the life of a structure.

The literature on stainless steel corrosivity identifies one ion as capable of causing pitting, stress corrosion cracking and intergranular corrosion in the 300 series of stainless steels and this happens to be the chloride ion. This susceptibility to chloride raises questions with regard to the performance of SSC reinforcement over the estimated 75-year life of a bridge. In addition, the cut bar ends have exposed mild steel and will be much more likely to corrode than the rest of the bar without some type of end treatment which will protect them. This corrosion could be exacerbated by the galvanic corrosion of dissimilar metals. At the same time, doubts have been raised concerning the performance of epoxy-coated reinforcement due to failures in high chloride environments within three years. Although the first epoxy-coated reinforcement bridge decks constructed in South Dakota exhibit no evidence of deterioration after more than twenty years, an attempt to evaluate their corrosion-resistance in situ was hampered by the lack of chloride ions at steel depth .

The purpose of this research is to evaluate the potential corrosion resistance, mechanical properties and uniformity of SSC using laboratory tests and, based on the results of these tests, design, construct and evaluate a bridge deck reinforced with stainless steel clad bars. All test results will be compared with epoxy-coated reinforcement. The research will provide information on the constructability and effectiveness of SSC bridge decks as well as performance, service life and cost-effectiveness data on both SSC and ECR systems.



Findings:

Research Objectives:
1  Determine the corrosion-resistance of SSC compared to EPR reinforcement as well as the mechanical properties, quality and suitability of SSC for use in bridge decks.
2  Develop design, construction, and evaluation procedures for building a bridge deck using SSC.
3  Estimate life expectancy and cost effectiveness of SSC, ECR and mild steel reinforcement in South Dakota.

Research Tasks:
1  Perform a literature search on 316L stainless steel and its use as reinforcement or as a cladding for reinforcement including a survey of any identified users of either form of stainless steel reinforcement.
2  Cooperatively develop a work plan including a testing plan.
3  Meet with the technical panel to discuss the project and scope of work.
4  Conduct a series of laboratory tests on SSC as outlined in the Virginia DOT draft specifications.
5  Conduct a series of statistically valid comparative tests of corrosion resistance on SSC/ECR/316L and mild steel reinforcement, all both with and without defects, to determine general corrosion properties both inside and outside concrete, stress and
6  Analyze corrosion effects on all types of steel tested as well as interfacial effects on SSC and ECR using scanning electron microscopy.
7  Provide evaluation of cladding uniformity, thickness variability and effects due to deformation profile on #4, #5 and #6 reinforcement randomly obtained.
8  Submit an interim report no later than August 31, 2000 estimating SSC and concrete service life and providing a recommendation of whether SSC should be incorporated into a bridge deck including any necessary modifications to design or construction pr
9  Develop a long-term evaluation plan, including any plan notes required for installation of testing instrumentation or samples, if necessary.
10  Monitor construction to observe constructability and insure any in-place monitoring equipment is properly installed.
11  Perform evaluation of structure during the first year after construction.
12  Prepare a final report and executive summary of the literature review, research methodology, findings, conclusions, estimated life for each steel type, evaluation plan and recommendations.
13  Make an executive presentation to the SDDOT Research Review Board at the conclusion of the project.

Documents Available:
SD2000_04.Final_Report.pdf

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