1. Stainless Steel Reinforcement as a Replacement for Epoxy Coated Steel in Bridge Decks ODOT-OkTC Transportation Research Day Oklahoma City, OK October 12, 2013

2. Outline Objectives Reinforcement Test methods and Results Life expectancy and Cost- effectiveness Conclusions and Recommendations

3. Determine the corrosion resistance of 2304 duplex stainless steel reinforcement and NX-SCR stainless steel clad bars compared to conventional and epoxy-coated reinforcement in reinforced concrete bridge decks Estimate the life expectancy and cost effectiveness of 2304 duplex stainless steel, NX-SCR stainless steel clad reinforcement, epoxy-coated reinforcement, and mild steel reinforcement in bridge decks in Oklahoma Objectives

4. Reinforcement Conv. ECR 2304 SS Clad

5. 2304 Pickled a second time As delivered

6. Test Methods Rapid Macrocell test Southern Exposure test Cracked Beam test

7. Chloride Induced Corrosion Two phase process: Phase I – initiation –Time to reach the critical chloride corrosion threshold Phase II – corrosion –Corrosion products build up around reinforcement Phase I Phase II Cracking of Concrete

8. Measurements and observations Voltage drop to measure corrosion rate Corrosion potential Mat-to-mat resistance Linear Polarization to measure microcell and macrocell corrosion Cl – content at corrosion initiation Cracking and staining of concrete Corrosion on bars following tests Evaluate disbondment of epoxy coating

9. Bench-Scale Tests

10. Southern Exposure Test

12. Cracked Beam Test

13. All bars – Southern Exposure

14. Corrosion resistant bars – Southern Exposure, different scale

15. Critical Chloride Corrosion Threshold Reinforcement No. of Samples Avg. Initiation Age (weeks) Avg. Chloride Content (lb/yd 3 ) Conventional3412.51.78 Conv./2304188.01.76 Conv./SSClad269.31.59 ECR3616.54.59 SSClad-4h5426.77.62 SSClad-- 23043599.820.5 2304/Conv.1475.020.5

16. All bars – Cracked Beam

17. Corrosion resistant bars – Cracked Beam, different scale

18. 2304– Cracked Beam

19. 2304 (pickled a second time) – Cracked beam

20. SS Clad– Cracked Beam

21. Cracked beams Conv. ECR 2304 SS clad

22. Comparisons based on: 150 ft span, 42 ft width, 8 in. deck 75 and 100-year economic lives ODOT costs

23. Time to first repair (years) 2 ½-in. cover Steel Designation Initiation Initiation to Cracking Cracking to Repair First Repair Conventional2.171019 ECR8.4351053 230444261080 2304-p-- 10> 100 SSClad-- 10> 100

24. Costs per yd 2 Present worth for 2% discount rate Steel Designation Initial Cost Total costs 75 years 100 years Conventional$163$1048$1265 ECR$198$422 2304$275 $423 2304-p$275 SSClad$240

25. Conclusions and Recommendations Corrosion resistant steels, even when damaged, provide significant advantages over conventional reinforcement Lack of proper pickling reduces corrosion resistance of stainless steel

26. Conclusions and Recommendations Some problems with NX-SCR TM stainless steel clad reinforcement – the bars are not currently available Stainless steel reinforcement should be pickled to a bright or uniformly light surface to ensure proper performance

28. The University of Kansas David Darwin, Ph.D., P.E. Deane E. Ackers Distinguished Professor and Chair Dept. of Civil, Environmental & Architectural Engineering 2150 Learned Hall Lawrence, Kansas, 66045-7609 (785) 864-3827 Fax: (785) 864-5631 daved@ku.edu