Presented By: Stephen R. Sharp, Ph.D., P.E.

1. Laboratory and Field Evaluations of Corrosion Resistance ReinforcementVirginia Concrete ConferenceBridge Breakout SessionMarch 4, 20119:00—9:30 a.m. Presented By: Stephen R. Sharp, Ph.D., P.E.

2. Overview • Information from several research projects • Corrosion Resistant Reinforcing Steel Testing • VCTIR • Stephen R. Sharp • VDOT – Materials Division • Larry J. Lundy , Harikrishnan Nair • Virginia Polytechnic Institute and State University • Cris D. Moen, Josiah Johnson, Brian Sarver • Route 123 Bridge over Occoquan River • Accelerated Test Method for CRR

3. Coated Alloyed Overview continued • VDOT Bridge-deck reinforcing steel type is changing • Higher performance concrete needs higher performance steel rebar • Methodology for accepting CRR is important • testing for alloying • mechanical properties • corrosion resistance

4. Why is it Important to Understand these Different Alloys? • Old Specification • One Rebar Grade – ASTM A615 Grade 60 • Differentiated by color • Black • Grey (galvanized) • Green/yellow/purple/etc. (epoxy-coated) • New Specification • Multiple alloy grades • ASTM A955 – multiple grades of stainless steel bar • ASTM A1035 – MMFX, etc. • AASHTO MP13 – Multiple grades of stainless steel clad bar

5. Lessons Learned: Many Varieties Cost of Bars Range from $0.33 up to $3.50 / lb.

6. Lessons Learned: Stainless Steel Cost • Alloyed steels are sensitive to alloy costs and some are more sensitive than others. • Steels with lower nickel and molybdenum provide greater price stability

7. Publications on Corrosion Resistance • FHWA, VCTIR & others have sponsored a number of studies • Different bars exhibit different levels of corrosion resistance

8. Lessons Learned: Visual Assessment of Different Bars Carbon steel MMFX2 Duracor • Different Types of Bars Can Look Similar

9. Lessons Learned: Visual Assessment of A Single Bar Type The Same Type of Steel Can Look Very Different

10. 2205 N 32 Lessons Learned: Manufacturers Markings Same bar markings, yet different alloys

11. Lessons Learned: Magnetic Response †Response measured using coating thickness gage 2205 316

12. Provides a means of quickly identifying the composition of rebar in the lab or field Performed following Manufacturers Guidelines Turn on x-ray fluorescence analyzer Allow to warm up for 5 minutes Perform Checks If XRF checks, proceed with analysis if not, calibrate instrument and recheck Alloy Identification Within Seconds longer analysis time for greater accuracy Total test time (warm-up + calibration) less than 10 minutes Provides alloy type,% confidence of alloy ID, list % elements detected, and confidence limit per element detected Lessons Learned: X-Ray Fluorescence

13. Lessons Learned: Visual Bar Assessment Care must be taken when accepting bars at the jobsite based on visual assessment and markings. • A magnet can be used as a rough sorting method to differentiate between magnetic and non-magnetic alloys. • Handheld XRF devices can be useful in determining alloy composition. • Industry should push ASTM to revise the standards that govern the bar markings and include a requirement that markings be added that indicate the type of steel.

14. Lessons Learned: Uniaxial Tensile Test

15. Lessons Learned: Elongation

16. Lessons Learned: Percent Reduction in Cross-Section

17. Relative Rib Area Measurements • ASTM A615 • Takes into account both the rib height and spacing Cord width measurement Rib spacing measurement Rib height measurement Bar diameter measurement

18. Lessons Learned: Example of Influence of Relative Rib Area Black: Rr = 0.80, NX (clad): Rr= 0.53 • Relative Rib Area Makes A Difference (From VTRC 04-R5)

19. Lessons Learned: Material Properties • Lesson Learned → Knowledge of the material properties and how each bar will interact with the concrete is important. • Alloying changes not only the corrosion resistance, but other material properties as well. • With several companies producing different types of bars, features vary and can result in different responses when loaded to failure • Differences in relative rib area • Debonding of clad from steel

20. Lessons Learned: Costs • The initial cost of CRR is a function of the reinforcement specified and ranges from about the same as ECR to 3 times more. • The additional initial cost of solid stainless CRR is typically less than 5 percent of the total project cost. • The cost of one deck overlay far exceeds the extra cost of solid stainless reinforcement.

21. Lessons Learned: ASTM A1035 • ASTM A1035-09 The chromium content range listed eliminates all candidate materials with a content greater than 10.9%

22. Lessons Learned: ASTM A955 • ASTM A955-06a • A955-09b & A955-10 Loss of ASTM A276 decreased the number of UNS designated stainless steel products by nearly 93%

23. Half-Cell, mV vs CSE No. of Points 1149 Median -92 Mean -101 Standard Deviation 51 Lessons Learned: Route 123 Bridge Deck 1.75”-2.25” Ave. Total Chloride, lb/yd3 • Uncracked • 0.380 • Cracked • 2.404 Resistivity, KΩ cm • No. of Points • 38 • Median • 57 • Mean • 55 • Standard Deviation • 16

24. Lessons Learned: Route 123 Bridge Deck continued

25. Lessons Learned: Route 123 Bridge Deck continued

26. Lessons Learned: Route 123 Bridge Deck continued

27. Lessons Learned: Route 360 Over Banister River, Halifax County • Void between clad layer and black steel core

28. Lessons Learned: Route 360 Over Banister River, Halifax County continued • Rust does not penetrate through the stainless cladding • Deep groove is present along the rolling direction, reducing clad thickness

29. Lessons Learned: Route 360 Over Banister River, Halifax County continued • Average Clad Thickness 0.7-mm  • Thinnest Value: 0.215-mm • Thickest Value (excluding stainless bulb area):1.351-mm

30. Placed Late 2001/Early 2002 End protection evaluation? Future Evaluation: Route 460 Over Route 29 Bypass, Campbell County (From VTRC 04-R5)

31. Summary • VDOT is implementing CRR • Visual assessment can not be relied on to determine bar type • Steel fabricator markings cannot be relied on to identify the type of steel. • Magnetic sorting provides a quick and easy method for differentiating between magnetic and nonmagnetic alloys.

32. Summary continued • X-ray fluorescence provides a practical, and much needed, method for positively identifying bars. • Relative rib area should be monitored as it varies from producer to producer. • Uniaxial tensile tests provide the stress-strain behavior, elongation and reduction in cross-section upon fracture can significantly vary for different CRR alloys.

33. Summary continued • Corrosion and mechanical testing of CRR is necessary to identify the most cost effective bars with acceptable properties. • Simple quality control measures need to be established to ensure VDOT receives the corrosion protection it needs • VDOT should evaluate using VTM for their acceptance criteria while pursuing a single CRR test method via AASHTO

34. Thank You – Questions? Acknowledgements: Federal Highway Administration, VDOT Materials Division, VDOT Structure and Bridge Division, University of Virginia, Virginia Center for Transportation Innovation and Research, and Virginia Polytechnic Institute and State University