Precision Estimates of AASHTO T267: Determination of Organic Content in Soils by Loss on Ignition (2010)

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ACKNOWLEDGMENT This work was sponsored by the American Association of State Highway and Transportation Officials (AASHTO), in cooperation with the Federal Highway Administration, and was conducted in the National Cooperative Highway Research Program (NCHRP), which is administered by the Transportation Research Board (TRB) of the National Academies. COPYRIGHT INFORMATION Authors herein are responsible for the authenticity of their materials and for obtaining written permissions from publishers or persons who own the copyright to any previously published or copyrighted material used herein. Cooperative Research Programs (CRP) grants permission to reproduce material in this publication for classroom and not-for-profit purposes. Permission is given with the understanding that none of the material will be used to imply TRB, AASHTO, FAA, FHWA, FMCSA, FTA, Transit Development Corporation, or AOC endorsement of a particular product, method, or practice. It is expected that those reproducing the material in this document for educational and not-for-profit uses will give appropriate acknowledgment of the source of any reprinted or reproduced material. For other uses of the material, request permission from CRP. DISCLAIMER The opinions and conclusions expressed or implied in this report are those of the researchers who performed the research. They are not necessarily those of the Transportation Research Board, the National Research Council, or the program sponsors. The information contained in this document was taken directly from the submission of the author(s). This material has not been edited by TRB.

iii CONTENTS   LIST OF TABLES ................................................................................................................................... IV  ACKNOWLEDGEMENTS ...................................................................................................................... V ABSTRACT .............................................................................................................................................. VI CHAPTER 1- INTRODUCTION AND RESEARCH APPROACH ..................................................... 7  1.1  Background............................................................................................................................. 7  1.2  Problem Statement ................................................................................................................. 7  1.3  Research Objectives ............................................................................................................... 7  1.4  Scope of Study ........................................................................................................................ 7  CHAPTER 2- DESIGN AND EXECUTION OF THE ILS .................................................................... 8  2.1  Test Specimens ....................................................................................................................... 8  2.2  Test Apparatus ....................................................................................................................... 8  2.3  Participating Laboratories .................................................................................................... 8  2.4  Interlaboratory Sample Preparation and Shipping ............................................................ 8  2.5  Interlaboratory Study Instructions ...................................................................................... 9  CHAPTER 3- INTERLABORATORY TEST RESULTS AND ANALYSIS ..................................... 10  3.1  Test Data ............................................................................................................................... 10  3.2  Method of Analysis ............................................................................................................... 10  3.3  Analysis of Results ............................................................................................................... 10  3.4  Statistical Tests for Significance ......................................................................................... 12  3.4.1  Comparison of the Measured and Target Averages ............................................ 12  3.4.2  Comparison of the Standard Deviations of Measurements ................................. 12  3.5  Combining of Similar Standard Deviations ....................................................................... 14  3.6  Precision Estimates of AASHTO T267 .............................................................................. 15  CHAPTER 4- CONCLUSIONS AND RECOMMENDATIONS ......................................................... 17  4.1  Conclusions ........................................................................................................................... 17  4.2  Recommendations ................................................................................................................ 18  REFERENCES .......................................................................................................................................... 19  APPENDIX A- INSTRUCTIONS AND DATA SHEET FOR AASHTO T267 ILS ........................... 20  APPENDIX B- ORGANIC CONTENT OF CLAY BLENDS AND COMPUTED ASTM E691 STATISTICS ............................................................................................................................................. 23  APPENDIX C- ORGANIC CONTENT OF SILT BLENDS AND COMPUTED ASTM E691 STATISTICS ............................................................................................................................................. 29  APPENDIX D- ORGANIC CONTENT OF SAND BLENDS AND COMPUTED ASTM E691 STATISTICS ............................................................................................................................................. 35  APPENDIX E- PRECISION STATEMENT FOR AASHTO T267 ..................................................... 41 

iv LIST OF TABLES Table 3-1: Summary of Statistics of organic content measurements ................................................... 11  Table 3-2: Summary of Statistics of organic content measurements after adjustment for the inherent organic content ........................................................................................................ 11  Table 3-3: Results of t-test for comparison of the average measured mass percentages with the added mass percentages of the organic material ................................................................. 12  Table 3-4: Results of F-test on comparison of within laboratory variability of measurements of clay for 1% level of significance .................................................................................................... 13  Table 3-5: Results of F-test on comparison of between-laboratory variability of measurements on clay for 1% level of significance ............................................................................................ 13  Table 3-6- Results of F-test on comparison of within laboratory variability of measurements on silt for 1% level of significance .................................................................................................... 13  Table 3-7: Results of F-test on comparison of between-laboratory variability of measurements on silt for 1% level of significance .............................................................................................. 14  Table 3-8: Results of F-test on comparison of within laboratory variability of measurements on sand for 1% level of significance ........................................................................................... 14  Table 3-9: Results of F-test on comparison of between-laboratory variability of measurements on sand for 1% level of significance ........................................................................................... 14  Table 3-10: Combined standard deviations of the soil blends with various organic contents ........... 15  Table 3-11: Results of F test for comparison of standard deviations of organic content measurements of various soil blends ..................................................................................... 15  Table 3-12: Precision estimates for measurement of organic content of soil ....................................... 16 

v ACKNOWLEDGMENTS The research reported herein was performed under NCHRP Project 9-26A by the AASHTO Materials Reference Laboratory (AMRL). Dr. Haleh Azari was the principal investigator on the study. Mr. Boran Altun, the Research Engineer, assisted with the preparation of the report. The author would like to thank Mr. Ron Holsinger for his help on the preliminary testing of the soils used in this study. The help of AMRL assessors in preparing the samples for the interlaboratory study is greatly appreciated. The author wishes to acknowledge the laboratories that participated in this study. Their willingness to volunteer their time and conduct the length measurements at no cost to the study is most appreciated. The laboratories include: State Department of Transportation Laboratories: Materials Research Park Florida DOT, Gainesville, FL Pima County DOT, Tucson, AZ Washington Department of Transportation Materials Laboratory, Tumwater, WA Florida Department of Transportation District 1 & 7 Materials Lab, Bartow, FL Florida Department of Transportation District 5 Materials & Research (Lab 393), Deland, FL Georgia Department of Transportation Office of Materials and Research, Forest Park, GA Virginia DOT-Materials Division, Bristol, VA Arizona DOT Materials Group, Phoenix, AZ North Carolina DOT Materials and Tests Unit Soils Laboratory, Raleigh, NC New Jersey Dept. of Transportation, Trenton, NJ Oregon Department of Transportation Materials Lab, Salem, OR Materials Research Park Soils and Foundation Lab Florida DOT, Gainesville, FL Virginia DOT Staunton Materials, Staunton, VA New York State Dept. of Transportation, Albany, NY Other Participating Laboratories: Wallace-Kuhl, West Sacramento, CA Geolab Services Pte Ltd, Singapore Patriot Engineering and Environmental, Inc., Indianapolis, IN The Mannik & Smith Group, Inc., Canton, MI, Professional Service Industries, Inc., Shreveport, LA Mortensen Engineering, Inc., Tampa, FL Dist. 3 Materials & Research Laboratory, Chipley, FL Louisiana Testing & Inspection, Inc., Scott, LA Nth Consultants, Ltd., Farmington Hills, MI Turnpike Materials (Lab 2058), Miami, FL American Engineering Testing, Inc., Saint Paul, MN Chicago Testing Laboratory, Inc., Elk Grove Village, IL Applied Geotechnical Engineering Consultants, St. George, UT Mactec Engineering & Consulting, Inc., Tampa, FL Geo Services, Inc., Arlington Heights, IL Materials Testing & Consulting, Inc., Olympia, WA

vi ABSTRACT This report presents the results of an interlaboratory study (ILS) to prepare precision estimates for the AASHTO T267 test method used for the determination of organic content in soils by loss of ignition. The materials for the ILS included sand, silt, and clay each blended with 2%, 5%, and 8% finely ground walnut shells as the organic material. A total of 27 laboratories provided results of percent organic content of three replicates of each soil-organic blend. The results indicated that the repeatability and reproducibility precisions are the same for different levels of organic content of each soil-organic blend, but significantly different for different soil types. A precision statement for AASHTO T267 is proposed based on the precision estimates computed in this study.