Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
1 CHAPTER 1- INTRODUCTION AND RESEARCH APPROACH 1.1 Background Under the National Cooperative Highway Research Program (NCHRP) Project 09-26A, the AASHTO Materials Reference Laboratory (AMRL) is conducting a multi- phase research project to determine or update estimates of precision for selected AASHTO test methods. The AASHTO T265 standard test method, âLaboratory Determination of Moisture Content of Soilsâ [1] is among the test methods that lack precision estimates. The T265 test method is used to determine moisture or water content of a soil, expressed as a percentage of the mass of water in a given mass of soil to the mass of the solid particles. An interlaboratory study (ILS) was designed to determine the precision estimates for AASHTO T265, which were incorporated in a precision statement provided in this report. 1.2 Problem Statement The accurate determination of in-situ moisture content of soil and aggregate is an important step in characterization of base and subbase materials for pavement construction. The level of precision in which percent moisture content of soil-aggregate mixture is measured has a significant effect on the method used for treating the base and subbase materials. Currently, there are no precision estimates that would define the accuracy requirements for water content measurements following AASHTO T265. Therefore, this study aims to determine repeatability and reproducibility precisions of soil-aggregate moisture content measured according to AASHTO T265 test method. 1.3 Research Objectives The overall objective of this study is to determine precision estimates for the AASHTO T265, âLaboratory Determination of Moisture Content of Soilsâ test method. The change in precision estimates for water content determination with the change in soil-aggregate gradation 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 four soil-aggregate blends using two different grading (coarse and fine) and two types of fillers (silt and clay) that satisfy the grading requirements of pavement base and subbase. b. Conduct preliminary testing on the selected materials. c. Select the laboratories participating in the ILS. d. Produce test specimens to send to the participating laboratories in the ILS.
2 e. Analyze results and develop precision estimates for moisture content determination. II. Recommend a precision statement for AASHTO T265 including the precision estimates developed from ILS data. III. Make conclusions and recommendations based on the findings of the study.
