Precision Estimates of AASHTO T265: Laboratory Determination of Moisture Content of Soils (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.

CONTENTS LIST OF TABLES ..................................................................................................................................... iii  ACKNOWLEDGMENTS .......................................................................................................................... v  ABSTRACT ................................................................................................................................................ vi  CHAPTER 1- INTRODUCTION AND RESEARCH APPROACH ..................................................... 1  1.1  Background............................................................................................................................. 1  1.2  Problem Statement ................................................................................................................. 1  1.3  Research Objectives ............................................................................................................... 1  1.4  Scope of Study ........................................................................................................................ 1  CHAPTER 2- Design and conduct of the ILS .......................................................................................... 3  2.1  Materials Selection ................................................................................................................. 3  2.2  Participating Laboratories .................................................................................................... 4  2.3  Interlaboratory Sample Preparation and Shipping ............................................................ 4  2.4  Interlaboratory Study Instructions ...................................................................................... 5  CHAPTER 3- INTERLABORATORY TEST RESULTS AND ANALYSIS ....................................... 6  3.1  Test Data ................................................................................................................................. 6  3.2  Method of Analysis ................................................................................................................. 6  3.3  Analysis of Results ................................................................................................................. 6  3.3.1  Coarse Blend with Clay ............................................................................................ 6  3.3.2  Coarse Blend with Silt .............................................................................................. 7  3.3.3  Fine Blend with Clay ................................................................................................. 7  3.3.4  Fine Blend with Silt ................................................................................................... 8  3.4  Tests for Statistical Significance ........................................................................................... 9  3.4.1  Comparison of the Average Measured and Target Moisture Contents ............... 9  3.4.2  Comparison of the Variability of Moisture Content Measurement ................... 11  3.4.3  Combined Standard Deviations of Various Moisture Levels .............................. 15  3.4.4  Precision Estimates of AASHTO T265 ................................................................. 16  CHAPTER 4- CONCLUSIONS AND RECOMMENDATIONS ......................................................... 17  4.1  Conclusions ........................................................................................................................... 17  4.2  Recommendations ................................................................................................................ 18  REFERENCES ......................................................................................................................................... 19  APPENDIX A- Instructions and Data Sheet for Interlaboratory Study ............................................. 20  APPENDIX B- Moisture Content of coarse with Clay aggregate-soil blend and computed ASTM E691 statistics ................................................................................................................. 23 

ii APPENDIX C- Moisture Content of coarse with silt aggregate-soil blend and computed ASTM E691 statistics ................................................................................................................. 28  APPENDIX D- Moisture Content of fine with Clay aggregate-soil blend and computed ASTM E691 statistics .......................................................................................................................... 33  APPENDIX E- Moisture Content of fine with silt aggregate-soil blend and computed ASTM E691 statistics .......................................................................................................................... 38  APPENDIX F- Precision Statement For AASHTO T265 ..................................................................... 43 

iii LIST OF TABLES Table 2-1: Gradations of ILS fine and coarse blends and Grading E and A of AASHTO M147 ........ 3  Table 2-2: Sources and classifications of ILS soil-aggregate blends according to AASHTO M145 .... 4  Table 2-3: Weights (g) of various components of the coarse-graded samples with clay (CC) ............. 5  Table 2-4: Weights (g) of different components of the coarse-graded samples with silt (CS) ............. 5  Table 2-5: Weights (g) of different components of the fine-graded samples with clay (FC) ................ 5  Table 2-6: Weights (g) of different components of the fine-graded samples with silt (FS) .................. 5  Table 3-1: Summary of Statistics of % moisture content of coarse aggregate with clay (CC) ............ 7  Table 3-2: Summary of Statistics of % moisture content of coarse blend with silt (CS) ...................... 7  Table 3-3: Summary of Statistics of % moisture content of fine blend with clay (FC) ........................ 8  Table 3-4: Summary of Statistics of % moisture content of fine blend with silt (FS) ........................... 9  Table 3-5: Results of t-test for comparison of measured and target moisture content of CC blend . 10  Table 3-6: Results of t-test for comparison of measured and target moisture content of CS blend .. 10  Table 3-7: Results of t-test on comparison of measured and target moisture content of fine aggregate with clay ................................................................................................................. 11  Table 3-8: Results of t-test on comparison of measured and target moisture content of FS blend ... 11  Table 3-9: Results of F-test on comparison of variability of moisture content measurements of coarse aggregate with clay (CC) and coarse aggregate with silt (CS), critical F value correspond to 1% level of significance .................................................................................. 12  Table 3-10: Pooled repeatability and reproducibility standard deviations of the clay and silt blends .................................................................................................................................................. 13  Table 3-11: Results of F-test on comparison of variability of moisture content measurements of FC and FS blends .......................................................................................................................... 13  Table 3-12: Pooled repeatability and reproducibility standard deviations of the clay and silt blends .................................................................................................................................................. 13  Table 3-13: Results of F-test on comparison of variability of moisture content measurements of coarse blends at various moisture contents .......................................................................... 14  Table 3-14: Results of F-test on comparison of variability of moisture content measurements at various moisture contents, fine aggregate with clay (FC), and fine aggregate with silt (FS) ........................................................................................................................................... 15 

iv Table 3-15: Computed standard deviations for water content measurement of coarse and fine blends ....................................................................................................................................... 15  Table 3-16: Results of F test for comparison of standard deviations of water content measurements of coarse and fine blends ........................................................................................................ 16  Table 3-17: Pooled standard deviations of the blends with various moisture content ....................... 16