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7 CHAPTER 1- INTRODUCTION AND RESEARCH APPROACH 1.1 Background As part of NCHRP 9-26, The AASHTO Materials Reference Laboratory has been conducting a series of research studies to determine or update estimates of precision for various AASHTO test methods. The AASHTO T267 âDetermination of organic content in soils by loss on ignitionâ [1] lacks precision estimates. Therefore, AASHTO Highway Subcommittee on Materials (HSOM) has requested that precision estimates be developed for this test method. An interlaboratory study (ILS) was designed to develop the precision estimates for AASHTO T267. 1.2 Problem Statement The engineering properties of soils are affected by organic materials. The determination of amount of organic content in soils is important in evaluation of base and subbase for a pavement construction. In this respect, the levels of accuracy and precision of organic content measurements would affect the overall performance of a pavement. The AASHTO T267 test method is currently lacking precision estimates that would define the accuracy requirements for the organic content determination. Therefore, the goal of this ILS study is to determine the repeatability and reproducibility precisions of organic content measurements in soils using the AASHTO T267 test method. 1.3 Research Objectives The overall objective of this study is to determine precision estimates for the AASHTO T267, âDetermination of Organic Content in Soils by Loss on Ignitionâ test method. The change in precision estimates of organic content with the change in mass percentage of organic material and soil type is also being investigated here. 1.4 Scope of Study The scope of the project involved the following major activities: I. Design and conduct an interlaboratory study (ILS): a. Select the soil types. b. Select the organic material. c. Select the laboratories to participate in the study. II. Analyze the measured data to determine the within laboratory and between laboratories variability. III. Develop precision estimates for AASHTO T267 test method based on the computed variability statistics. IV. Prepare a precision statement for AASHTO T267 using the developed precision estimates. V. Make conclusions and recommendations based on the findings of the study
