Acceptance Procedures for New and Quality Control Procedures for Existing Types of Corrosion-Resistant Reinforcing Steel

About the report:

As the Virginia Department of Transportation (VDOT) continues to move forward with implementing the use of corrosion-resistant reinforcing (CRR) bars, it is important for VDOT to have a means of characterizing the candidate bars as well as ensuring that the quality of approved CRR bars is preserved.  This is vital to ensure the bars respond physically in a manner that is consistent with VDOT’s expectations.  The purpose of this study was to provide VDOT’s Materials Division with a method/specification for evaluating CRR bars. 

The study determined that visual assessment cannot be relied on to determine bar type.  Further, steel fabricator markings cannot be relied on to identify the type of steel.  However, when questions arise regarding the identification of bars, magnetic sorting provides a quick and easy method for differentiating between magnetic and nonmagnetic alloys.  If more quantitative results are required, X-ray fluorescence provides a practical and much-needed method for positively identifying bars.

Physically, the bars differ among producers.  Relative rib area should be monitored as it also varies among producers.  Further, alloying changes not only the corrosion resistance but also other important properties.  The results of uniaxial tensile tests showed that the stress-strain behavior, elongation, and reduction in cross-section upon fracture could vary significantly for different CRR alloys.  Therefore, mechanical testing, in addition to corrosion testing, of CRR is necessary to identify the most cost-effective bars with acceptable properties.

Finally, the study determined that quality control measures need to be established to ensure VDOT receives the corrosion protection it needs.  Further, care should be taken when relying upon international standards for acceptance criteria. 

The report recommends that VDOT’s Materials Division implement the set of test methods provided in the appendices of this report as Virginia Test Methods for CRR acceptance criteria.  To simplify the implementation of CRR in Virginia and elsewhere, VDOT’s Materials Division should work with the American Association of State Highway and Transportation Officials to develop a single specification for the testing and acceptance of CRR.  VDOT’s Materials Division should also investigate retrofitting the uniaxial tensile test equipment with a non-contact extensometer to guarantee that stress vs. strain measurements of CRR can be made and ensure the yield strength is determined.

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