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1 CHAPTER 1- INTRODUCTION AND RESEARCH APPROACH 1.1 Background The AASHTO Materials Reference Laboratory has been conducting the NCHRP 9-26A research project to determine or update estimates of precision for AASHTO test methods that lack precision statement or need update of precision estimates. Since T148 test method âMeasuring Length of Drilled Concrete Coresâ [1] lacks precision estimates, AASHTO Highway Subcommittee on Materials (HSOM) has requested that precision estimates be developed for this test method. A round robin study was conducted to collect length measurement data of drilled concrete cores for determining within-laboratory and between-laboratory precision estimates for AASHTO T148. The precision statistics computed from the round robin study were incorporated in the AASHTO T148 precision statement proposed in this report. 1.2 Problem Statement The measurement of pavement thickness is an important aspect of determining if concrete construction is in compliance with design specifications. Therefore, the precision and accuracy of the measurements has a significant effect on the acceptance of a constructed concrete pavement and consequently on its performance as a whole. However, the AASHTO T148 test method that should define the accuracy requirements for measuring length of drilled concrete elements lacks precision estimates. Therefore, the purpose of this study is to determine the repeatability and reproducibility precision of drilled concrete cores length measurements following AASHTO T148 test method. 1.3 Research Objectives The overall objective of this study is to determine precision estimates for the AASHTO T148, âMeasuring Length of Drilled Concrete Coresâ test method. The effect of the core surface condition and dimensions on the single-operator and multi-laboratory precision estimates are also being investigated. 1.4 Scope of Study The scope of the project involved the following major activities: I. Design and conduct a round robin study: a. Select drilled cores for length measurements. b. Select 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 T148 test method based on the computed variability statistics. IV. Prepare a precision statement for AASHTO T148 using the developed precision estimates. V. Make conclusions and recommendations based on the findings of the study.
