“Old Wooden Bridge” Bridge to No Name Key from Big Pine Key, Florida

1. “Old Wooden Bridge” Bridge to No Name Key from Big Pine Key, Florida

2. Precision Statements for the Surface Resistivity of Water Cured Concrete Cylinders in the Laboratory by Mike Jackson for Mario Paredes

3. Sponsors • American Association of State Highway and Transportation Officials (AASHTO); • Technology Implementation Group (TIG); • Florida Department of Transportation; • TRB Committee AFN30 – Durability of Concrete.

4. Participants • California Department of Transportation; • Colorado Department of Transportation; • Federal Highway Administration; • Florida Department of Transportation; • Florida Atlantic University; • Grupo Carmelo, Puerto Rico; • Indiana Department of Transportation; • McGill University;

5. Participants (Continued) • Nebraska Department of Transportation; • New York Department of Transportation; • Puerto Rico Highways and Transportation Authority; • Purdue University; • Titan America –Tarmac; • The University of North Florida; and • Virginia Department of Transportation.

6. Round-Robin Testing Program • ASTM Designation C802, “Standard Practice for Conducting an Interlaboratory Test Program to Determine the Precision of Test Methods for Construction Materials.” • AASHTO Designation: TP95-11, “Standard Method of Test for Surface Resistivity Indication of Concrete’s Ability to Resist Chloride Ion Penetration2.”

7. Round-Robin Testing Program • Fourteen (14) different laboratories; • Twelve (12) different concrete mixtures; • Wide range of constituent materials; and • Two (2) different commercial SR meters: • CNS Farnell Ltd. • Proceq SA.

8. Concrete Mix Constituents

9. Concrete Mix Constituents • Mix w/cm ratios ranged from 0.30 - 0.41; • Ten of the12 mixes contained fly ash; • One mix contained no granular admixtures; • One mix contained 25% slag; • One mix contained 10% meta-kaolin; and • Two mixes contained 4% - 6% silica fume.

10. Test Samples • Hardened 4-in. diameter by 8-in. long cylindrical concrete specimens were tested; • Test specimens were fabricated by 12 of the participating labs, and shipped to all participants for SR testing; • SR was measured in accordance with AASHTO Designation: TP95-11 after 28, 56, and 91 days of standard laboratory curing.

11. Sample Packaging • After 2 weeks of curing in lime saturated water, specimens were wrapped and sealed to avoid loss of moisture during shipping.

12. Sample Shipping • The specimens were then carefully packaged for 2nd Day shipping to avoid damage and/or drying during shipping.

13. Surface Resistivity Testing • SR was then measured after 28, 56, and 91 days of standard laboratory curing.

14. Example SR Test Results

15. Mean SR at 28 Days Note: Data shaded in yellow determined to be statistical stragglers by Mandel’s k-statistic.

16. Std. Dev. at 28 Days Note: Data shaded in yellow determined to be statistical stragglers by Mandel’s k-statistic.

17. Mandel’s k-statistic at 28 Days

18. Mandel’s k-statistic at 56 Days

19. Mandel’s k-statistic at 91 Days

20. Mandel’s h-statistic at 28 Days

21. Mandel’s h-statistic at 56 Days

22. Mandel’s h-statistic at 91 Days

23. Precision Calculationsat 28 Days Note: Lab #7 Data Removed Based on Mandel’s h-statistic.

24. Precision Estimatesat 28, 56, and 91 Days

25. Precision Statements

26. Proposed Precision Statements • Single-Operator Precision – The results of two properly conducted tests by the same operator on concrete samples from the same batch and of the same diameter should not differ by more than 12.1% of their average. • Multilaboratory Precision – The results of two properly conducted tests in different laboratories on the same material should not differ by more than 32.5% of their average. • Bias - This procedure has no measurable bias.

27. Equipment Equivalence

28. Paper Published in the Journal of ASTM International, Paper ID #JAI104268-11, “Precision Statements for the Surface Resistivity of Water Cured Concrete Cylinders in the Laboratory.”