Distribution of Chloride, pH, Resistivity, and

Sulfate Levels in Backfill for Mechanically-

Stabilized Earth Walls and Implications for

Corrosion Testing

BDV25-977-03

Mr. Ivan Sokolic, Project Manager Construction Manager

FDOT Ft. Myers Operations CenterDistrict One

2981 N. E. Pine Island Road

Cape Coral, Florida 33909

Dr. Manjriker Gunaratne, Principal Investigator Chair

Department of Civil & Environmental Engineering

University of South Florida

4202 E. Fowler Avenue

Tampa, Florida 33620

Final Report Performance Period: June 3, 2013 through May 31, 2015

May 2015

Prepared by

Noreen Poor, Manjriker Gunaratne, and Thilanki Rajaguru

University of South Florida, Tampa, Florida

ii

Disclaimer

The opinions, findings, and conclusions expressed in this publication are those of the authors and

not necessarily those of the State of Florida Department of Transportation.

iii

Approximate Conversions to SI Units

SYMBOL WHEN YOU KNOW MULTIPLY BY TO FIND SYMBOL

LENGTH

mm millimeters 0.039 inches in

m meters 3.28 feet ft

m meters 1.09 yards yd

km kilometers 0.621 miles mi

SYMBOL WHEN YOU KNOW MULTIPLY BY TO FIND SYMBOL

AREA

mm2 square millimeters 0.0016 square inches in

2

m2 square meters 10.764 square feet ft

2

m2 square meters 1.195 square yards yd

2

ha hectares 2.47 acres ac

km2 square kilometers 0.386 square miles mi

2

SYMBOL WHEN YOU KNOW MULTIPLY BY TO FIND SYMBOL

VOLUME

mL milliliters 0.034 fluid ounces fl oz

L liters 0.264 gallons gal

m3 cubic meters 35.314 cubic feet ft

3

m3 cubic meters 1.307 cubic yards yd

3

SYMBOL WHEN YOU KNOW MULTIPLY BY TO FIND SYMBOL

MASS

g grams 0.035 ounces oz

kg kilograms 2.202 pounds lb

Mg (or "t") megagrams (or "metric

ton")

1.103 short tons (2000 lb) T

SYMBOL WHEN YOU KNOW MULTIPLY BY TO FIND SYMBOL

TEMPERATURE (exact degrees)

oC Celsius 1.8C+32 Fahrenheit

oF

*SI is the symbol for the International System of Units. Appropriate rounding should be made to comply with

Section 4 of ASTM E380.

(Revised March 2003)

(Downloaded from http://www.fhwa.dot.gov/aaa/metricp.cfm January 2015)

http://www.fhwa.dot.gov/aaa/metricp.cfm%20January%202015

iv

Technical Report Documentation Page 1. Report No.

2. Government Accession No.

3. Recipient's Catalog No.

4. Title and Subtitle

Distribution of Chloride, pH, Resistivity, and Sulfate Levels in

Backfill for Mechanically-Stabilized Earth Walls and

Implications for Corrosion Testing

5. Report Date

6. Performing Organization Code

7. Author(s) Noreen Poor, Manjriker Gunaratne, Thilanki Rajaguru

8. Performing Organization Report No.

9. Performing Organization Name and Address

Department of Civil & Environmental Engineering University of South Florida

4202 E. Fowler Avenue

Tampa, Florida 33620

10. Work Unit No. (TRAIS)

11. Contract or Grant No.

BDV25-977-03 12. Sponsoring Agency Name and Address

Florida Department of Transportation

605 Suwannee Street, MS-30

Tallahassee, Florida 32399

13. Type of Report and Period Covered

Final Report

06/03/2013 to 05/31/2015

14. Sponsoring Agency Code

15. Supplementary Notes

16. Abstract

The ultimate goals of this research were to improve quality, speed completion, and reduce risk in mechanically-stabilized

earth (MSE) wall projects. Research objectives were to assure (1) that variability in the corrosion properties of soil (pH,

minimum resistivity, chloride, and sulfate levels) due to sampling and analytical technique was much lower than variability

in these levels within and between soil sources and types and thus did not inflate the risk of emplacing a corrosive soil as

MSE wall backfill, (2) that the number of soil type samples analyzed prior to acceptance of a backfill was appropriate, based

on the expected distribution of corrosion properties within the backfill, and (3) that the corrosion properties of backfill

material did not change appreciably over time, especially after emplacement and over the design lifetime of an MSE wall.

Corrosion properties of soil were tested with Florida Methods (FMs) 5-550, 5-551, 5-552, and 5-553 for pH, minimum

resistivity, water-soluble chloride, and water-soluble sulfate, respectively. Changes to the quality assurance (QA) plan for

acceptance quality characteristics (AQC) of backfill corrosion properties were recommended based on research outcomes.

These changes had as their focus an improvement in the buyers statistical power to accept good backfill material through

reductions in test error associated with material properties, sample processing, and laboratory procedures. Recommended

changes included (1) proposed revisions to the FMs for pH, minimum resistivity, chloride, and sulfate, (2) an increase in the

number of independent samples tested for pH and minimum resistivity, (3) a revised acceptance limit for minimum

resistivity, (4) method operator training and independent audits, (5) an inter-laboratory study post-implementation of the

revised methods, and (6) re-evaluation of the need for chloride and sulfate testing for backfill above a pre-determined

minimum resistivity. Geochemical modeling with the U. S. Geological Survey (USGS) model PHREEQC for a conservative case of a low ionic strength and poorly buffered sandy backfill revealed that in a few years time the pore water

of emplaced backfill could equilibrate with infiltrating rainfall. The model results suggested that a soils buffering capacity

might be important consideration when metal is used as reinforcement in MSE wall backfill. Field and laboratory testing of

candidate sands to calibrate the model were recommended ahead of any proposed changes to the QA plan based on model

results. 17. Key Word

Mechanically-stabilized earth (MSE) wall, corrosion, pH,

resistivity, chloride, sulfate, select backfill, ruggedness

study, inter-laboratory study

18. Distribution Statement

No restrictions.

19. Security Classif. (of this report)

Unclassified

20. Security Classif. (of this page)

Unclassified

21. No. of Pages

378 22. Price

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized

v

Acknowledgments

The authors of this report would like to express their gratitude for access to mines from which we

collected soil samples, and we would like to thank mine owners and operators that gave us that

access: Angelos Recycled Materials, Dade City; C. C. Calhoun, Haines City; Cemex Alico Quarry,

Ft. Myers; Hickey Excavation, Sebring; Jahna Industries, Haines City; Titan Florida Center Sand,

Clermont; Transcor Dirt Services, Wimauma; and Youngquist Brothers Rock Mine, Ft. Myers. We

would also like to thank the commercial laboratories that opened their laboratories for a visit or

participated with a split-sample analysis. These laboratories included Environmental &

Geotechnical Specialists (EGS), Tallahassee; Ellis & Associates, Jacksonville; Universal

Engineering Services (UES), Jacksonville; Universal Engineering Services (UES), Orlando;

Professional Service Industries (PSI), Orlando; Madrid Engineering, Bartow; Professional Service

Industries (PSI), Tampa; Tally Engineering, Tampa; Tierra, Tampa; Universal Engineering

Services (UES), Tampa; Ardaman & Associates, Ft. Myers; and Professional Services Industries

(PSI), Ft. Lauderdale. We would like to extend our sincere appreciation for the help received from

the FDOT facilities that allowed two laboratory visits and participated in the inter-laboratory study:

Districts 1 and 7 Materials Office Laboratory, Bartow; District 2 Materials Office Laboratory,

Lake City; District 3 Materials Office Laboratory, Chipley; Districts 4 and 6 Materials Office

Laboratory, Davie; District 5 Materials Office, Deland; and the State Materials Office (SMO)

Corrosion Laboratory and Environmental Laboratory, Gainesville. The authors would like to thank

Ingrid Eversley, Barbara Johnson, Melissa Lopez, Carol Marrero-Placeres, Julie McCoy and

Shivali Vyas, USF College of Engineering, for their assistance with purchasing and travel. Finally,

we would like to thank project team membersformal and informalfor their enthusiasm and

support of this project. These team members included Project Manager Ivan Sokolic, Sam Joseph,

Timothy Meeks, Xiaoyan Zheng, Teresa Puckett, and Angela Koloc, FDOT Districts 1 and 7

Materials Office; Mario Paredes (retired from FDOT), David Horhota, Ronald Simmons, and

Nikita Reed, State Materials Office; Patti Brannon and Latashi Kitchen, FDOT Research Office;

and Corinne Walters and Stephanie Rios, USF Sponsored Research. This research would not have

been possible without the assistance provided by courteous and professional staff of mine owners

and operators, commercial laboratories, USF departments, and FDOT offices.

vi

Executive Summary

The ultimate goals of this research were to improve quality, speed completion, and reduce risk in

mechanically-stabilized earth (MSE) wall projects. Research objectives