Improved Test Methods and Practices for Characterizing Steel Corrosion Potential of Earthen Materials (2020)

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Contents Summary .........................................................................................................................................1 Chapter 1. Background .................................................................................................................7 1.1. Introduction ..........................................................................................................................7 1.2. Research Objectives .............................................................................................................7 1.3. Review of Current Practices for the Characterization of Corrosion Potential of Earthen Materials .................................................................................................................8 1.3.1 Factors Affecting the Corrosion Potential of Geomaterials ...........................................8 1.3.2 Current Laboratory Test Methods ..................................................................................9 1.3.2.1 Comparison of Different Resistivity Test Methods ..................................................10 1.3.3 Limitations of Current Test Methods ...........................................................................15 1.4. Knowledge Gaps and Study Purpose ................................................................................15 Chapter 2. Research Approach ..................................................................................................16 2.1. Introduction ........................................................................................................................16 2.2. Phase I ................................................................................................................................16 2.2.1 Task 1 – Information Search ........................................................................................16 2.2.2 Task 2 – Identify Limitations of Approaches for Characterizing Materials ................16 2.2.3 Task 3 – Developed Detailed Work Plan .....................................................................16 2.2.4 Task 4 – Submit Interim Report...................................................................................16 2.3. Phase II ...............................................................................................................................17 2.3.1 Task 5 – Conduct Work Plan Approved in Task 4 ......................................................17 2.3.2 Task 6 – Prepare Work Plan for Field Trials ...............................................................17 2.4. Phase III ..............................................................................................................................17 2.4.1 Task 7 – Implement Work Plan for Field Trials ..........................................................17 2.4.2 Task 8 – Propose Protocol ...........................................................................................17 2.4.3 Task 9 – Prepare Final Report .....................................................................................17 Chapter 3. Laboratory Measurements (Phase II) .....................................................................18 3.1. Introduction ........................................................................................................................18 3.2. Description of Data Set ......................................................................................................18 3.3. Comparison of Results from Different Test Methods ........................................................22 3.3.1 Resistivity ....................................................................................................................22 3.3.1.1 Precision/Repeatability for Individual Test Methods ...........................................23 3.3.1.2 Comparison of Different Resistivity Tests with AASHTO T-288 (2016) ...........24 3.3.2 Salt Contents ................................................................................................................29 3.3.2.1 Correlations between Salt Contents and Resistivity .............................................31 3.3.3 Measurements of pH ....................................................................................................34 3.4. Characterization of Corrosion Potential and Correlations with Corrosion Rates ..............36 3.4.1 Correlation between Resistivity and Performance Data ..............................................37 3.4.1.1 Performance of Galvanized Steel .........................................................................38 3.4.1.2 Performance of Plain Steel ...................................................................................41 3.4.2 Classification of Soil Corrosivity.................................................................................42 3.4.2.1 Characterization Scheme ......................................................................................42 3.4.2.2 Correlation between Results of Characterization Scheme and Performance Data .................................................................................................46 3.5. Recommended Protocol .....................................................................................................49

Chapter 4. Field Measurements (Phase III) ..............................................................................51 4.1. Introduction ........................................................................................................................51 4.2. Description of Data Set ......................................................................................................51 4.3. Results ................................................................................................................................55 4.3.1 Resistivity – Soil Boxes ...............................................................................................55 4.3.2 Resistivity – Field Tests using Wenner Technique ......................................................57 4.3.3 Other Electrochemical Properties ................................................................................63 4.4. Comments and Suggestions from Owners .........................................................................65 4.5. Conclusions ........................................................................................................................66 Chapter 5. Conclusions and Needs for Future Research .........................................................68 5.1. Main Conclusions ...............................................................................................................68 5.2. Recommendations for Future Research .............................................................................69 References .....................................................................................................................................72 Appendix A. Test Protocols – Recommended Electrochemical Test Methods to Evaluate the Corrosion Potential of Earthen Materials ......................................................75 Appendix B. Details of Laboratory Measurements ..................................................................83

vi List of Figures Figure 1-1 Resistivity measurement using a two-electrode soil box. 12 Figure 1-2 Resistivity versus moisture contents (adapted from McCarter, W.J. (1984)). 12 Figure 1-3 Procedure to perform a typical leach test. 14 Figure 3-1 Characteristics of the sample domain used in the laboratory investigations. 21 Figure 3-2 Summary of the test results for measuring resistivity/conductivity 23 (a) precision (b) bias with respect to AASHTO T-288. Figure 3-3 Comparisons of soil box test results relative to AASHTO T-288. 25 Figure 3-4 Statistics of resistivity test bias with respect to AASHTO T-288 (2016) (a) bias means and standard deviations 25 (b) coefficients of variation (COV = σbias/μbias) 26 Figure 3-5 Resistivity measurements from samples with different textures (a) mean bias 27 (b) coefficients of variation 28 Figure 3-6 Tests for measurements of salt content, and observations of precision. 30 Figure 3-7 Correlation between salt content measurements from Tex-620-M and AASHTO T-290 & T-291. 31 Figure 3-8 Summary of the test results for measuring pH 35 (a) precision (b) bias with respect to AASHTO T-289 (2018) Figure 3-9 Comparisons of pH measurements relative to AASHTO T-289 (2018). 36 Figure 3-10 Galvanized steel corrosion rates and resistivity measurements from Samples with more than 22% passing the No.10 sieve (via AASHTO T-288 (2016)) 39 Figure 3-11 Galvanized steel corrosion rates and measurements of resistivity from samples with less than 22% passing the No.10 sieve (via Tex-129-M) 40 Figure 3-12 Galvanized steel corrosion rates and measurements of resistivity from worldwide data. Testing with AASHTO T-288 (2016) from samples with more than 22% passing the No.10 sieve 41 Figure 3-13 Plain steel corrosion rates and measurements of resistivity from AASHTO T-288 (2016) and samples with more than 22% passing the No.10 sieve. 42 Figure 3-14 Flowchart of the proposed protocol. 50 Figure 4-1 Locations and coordinates of construction sites. 53 Figure 4-2 Gradation curves from different sources. 54 Figure 4-3 Resistivity measurement using modified soil box. (a) Schematic 55 (b) Test Set-up 56 Figure 4-4 Comparison of resistivity results obtained from modified soil box tests. 56 Figure 4-5 The Wenner 4-probe technique. (a) Schematic 57 (b) Test setup in the field 58 Figure 4-6 Locations, zones and directions for performing soil resistivity measurements.

vii (a) San Antonio, TX 58 (b) El Paso, TX 59 (c) Buffalo, NY 59 (d) Schroon, NY 59 Figure 4-7 Results from in-situ testing. (a) San Antonio, TX – parallel to reinforcements 60 (b) San Antonio, TX – perpendicular to reinforcements 60 (c) El Paso, TX – parallel to reinforcements 60 (d) El Paso, TX – perpendicular to reinforcements 60 (e) Buffalo, NY – parallel to pavement 61 (f) Buffalo, NY – perpendicular to pavement 61 (g) Schroon, NY – parallel to pavement 61 (h) Schroon, NY – perpendicular to pavement 61 Figure 4-8 In-situ measurement of moisture content at Schroon, NY. 62 Figure 4-9 Extrapolating the moisture-resistivity curves to determine the resistivity at in-situ moisture content for the site in Buffalo, NY. 63 Figure 4-10 Comparison of chloride content results obtained from samples collected from the sites and sources 64 Figure 4-11 Comparison of sulfate content results obtained from samples collected from the sites and sources 65 Figure 4-12 A mixer used in at Soils Engineering Laboratory of NYSDOT 66 Figure B-1 Histogram of bias in salt measurements fromTex-620-M 89 Figure B-2 Correlation between bias in salt measurements fromTex-620-M and percent passing the No. 10 sieve used to characterize the sample. 90 Figure B-3 Correlation of bias from Tex-129-M with respect to scaling parameter. 93

viii List of Tables Table 1-1 AASHTO requirements for the fill materials in MSE walls. 9 Table 1-2 Comparison of different resistivity test methods in terms of sample treatment. 13 Table 1-3 Differences in test methods performed on extracts (leachates). 14 Table 3-1 Summary of sample sources 19 Table 3-2 Resistivity test bias correspondence with GN and PP#10. 28 Table 3-3 Resistivity model parameters (ppm of salts). 33 Table 3-4 Resistivity model parameters (mEq of salts and carbonates). 33 Table 3-5 Regression of observed corrosion rates and resistivity measurements. 38 Table 3-6 Characterization scheme from DVGW GW9. 44 Table 3-7 Soil corrosivity/aggressiveness (for carbon steel) DIN 50 929 Part 3. 45 Table 3-8 Expected corrosion forms/rates (for carbon steel) DIN 50 929 Part 3. 45 Table 3-9 Data clustering according to resistivity and observed rates of corrosion. 47 Table 3-10 Ranges of corrosion rate according to resistivity. 47 Table 3-11 Data clustering for corrosivity rankings to observed rates of corrosion. 48 Table 3-12 Ranges of corrosion rate and corresponding ranges of Æ©(I). 48 Table 4-1 Laboratory tests performed on the site and source samples. 52 Table 4-2 Summary of gradations from different sources 54 Table 4-3 In-situ (Wenner 4-probe) and laboratory (modified soil box) measurements. 63 Table 4-4 Characterization of corrosion potential. 64 Table B-1. Summary of state practices. 83 Table B-2. Summary of resistivity tests, precision, and bias. 84 Table B-3. Statistics of resistivity test bias with respect to AASHTO T-288 (2016). 85 Table B-4. Bias of resistivity measurements from samples with different texture. 85 Table B-5. Tests for measurements of salt content, and observations of precision. 86 Table B-6. Summary of tests for pH and observations of precision and bias. 87 Table B-7. Summary of salt contents measured via AASHTO and Texas modified procedures. 88

ix Author Acknowledgements The research reported herein was performed under NCHRP Project 21-11 by McMahon & Mann Consulting Engineering and Geology, P.C. (McMahon & Mann) and the University of Texas at El Paso (UTEP). Dr. K.L. Fishman, P.E. from McMahon & Mann was the principal investigator and Professors S. Nazarian, S. Walker, and A. Bronson from UTEP were co-principal investigators. Personnel from McMahon & Mann including Messrs. Cody Coonradt, Jim Bojarski, P.E., Chad Giesler, Jon Whiting, Brad Armstrong, P.E., and Ms. Kaitlyn Murray, P.E. and Sonia Pang assisted with the literature review, sampling, and data analyses for the project. Dr. Hamid Fakhri from McMahon & Mann was instrumental in implementing the verification study conducted in Phase III of this research and in preparing this report. We are grateful to the many graduate and undergraduate research assistants from UTEP who undertook the extensive laboratory test program that was a large part this research including Jose Luis Arciniega Aguilar, Diana Cabrara, Troy Svede, Mathew Gonzales, Luisa Morales, Daniela Hernandez, Yadira Calderas, Miguel Perez, and Luis Lemus. The lab technicians from UTEP including Jose Garibay, Sergio Rocha, and Cesar Tirado are also acknowledged for their contributions to the laboratory test program as well as for collecting information from the Texas sites incorporated into the implementation study conducted during Phase III. We received considerable assistance to procure samples of fill for the laboratory test program from the New York State Department of Transportation (NYSDOT), the North Carolina Department of Transportation (NCDOT), the Florida Department of Transportation (FDOT), the Expanded Shale, Clay and Slate Institute (ECSI) and from contactors and aggregate suppliers in New York, South Carolina; British Columbia, Canada, and Alberta, Canada. Samples of fill were obtained from in service MSE structures and involved the use of excavation equipment, drilling equipment, traffic control, associated crews and utility clearances that were donated as part of the assistance provided by these agencies. Personnel from these agencies who contributed include Joe DiGregorio, P.E., (NYSDOT, Structure Foundations Section Supervisor), Chris Nebral P.E. (NYSDOT, Geotechnical Engineering Bureau, Geotechnical Engineer), Joe SantaMaria, P.E. and Tim Wolff, P.E. (NYSDOT, Region 2, Regional and Assistant Geotechnical Engineer), Darryl Byers, P.E. (NYSDOT, Region 4, Geotechnical Engineer), Todd Nelson, P.E. (NYSDOT, Region 5, Geotechnical Engineer), John Wheeler (NYSDOT, Region 8, Construction), Aquifer Drilling and Testing, Inc. (NYSDOT, Region 8, drilling contractor); Messrs. Brian Hunter, Cabell Garbee, and Todd Whittington (NCDOT, Materials and Test Unit); Dr. Mohammed Mulla, P.E., and Messrs. Scott Hidden, P.E. and John Pilipchuk P.E. (NCDOT, Geotechnical Engineering Unit), Messr. Kyle Brashear, (QA Supervisor, North Carolina East District, Martin Marietta, Clark Quarry, New Bern, North Carolina); Messr. Rodrigo Herrera, P.E. (FDOT, Structures Design Office), Dr. David Horhota (FDOT, State Geotechnical Materials Engineer), Messr. Ron Simmons (FDOT, State Materials Office), and the FDOT District 5, Ocala Operations Office; Messr. John Johnson, P.E., (Project Manager, CDM Smith, Inc., SCDOT, Horry County DPW), Messr. Brian Bennett (Project

x Manager, Windley Contacting, Ltd., British Columbia, CA); Messr. Barre Johnson (Kiewit Graham Ledcor Constructors, Calgary, Alberta CA); and Messrs. Bill Wolfe and Jack Moore (ESCSI). Ms. Monica Ruiz and Messr. Richard Izzo (TXDOT); Messrs. Mathew Van Wicklen and Jacob Fuentes, P.E. (Raba Kistner Consultants, Inc.); Messrs. Joe DiGregorio, P.E., (NYSDOT, Structure Foundations Section Supervisor) and Brett Dening, (NYSDOT Soils Engineering Laboratory Supervisor) graciously facilitated access to sites included in the implementation study for Phase III, provided much needed background information for the sites, and performed sampling and laboratory testing for comparison with the results from the research team. The authors are sincerely grateful to the members of the Association for Mechanically Stabilized Earth (AMSE) for the helpful comments, discussions and feedback during the course of this research.