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Abstract
Hot-mix asphalt (HMA) sampling is a critical step in quality control and quality assurance (QC/QA) programmes to ensure that the tested material is representative of the installed product. Samples of HMA in illinois are currently taken from a truck at the plant. This sampling method allows for a quick turnaround time because the QC laboratory is usually located at the plant. However, it may be difficult to obtain a representative sample because most of the sample is taken from the top of the pile and from the side closest to the sampling platform. In addition, this sampling method does not account for any additional asphalt absorption taking place during transportation and placement. The concept of moving the sample location to the job site offers the potential to address the weaknesses cited above. However, there are a number of different approaches, each with advantages and disadvantages. The objective of this study was to provide a review of successful methods and practices currently used to sample HMA during production and installation. This included visiting other states and collecting sufficient data to draw a final recommendation for the optimum technique to be adopted for HMA sampling in illinois. The conclusion of the field visits was that sampling behind the paver is being successfully conducted by many states without difficulty. On the basis of the presented review of methods and practices currently used to sample HMA during production and installation, this study recommends that the level of variability between the samples obtained from different sampling techniques should be quantified. The level of variability as well as the practical aspects of the different sampling techniques as identified in this study should be used to support the selection of one of the presented methods and its possible implementation in illinois.
Acknowledgements
This study is based on the results of ICT-R27-8, evaluation of hot-mix asphalt sampling techniques. ICT-R27-8 was conducted in cooperation with the Illinois Center for Transportation; the Illinois Department of Transportation, division of highways; and the U.S. Department of Transportation, Federal Highway Administration. The contents of this report reflect the view of the authors who are responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the Illinois Department of Transportation or the Federal Highway Administration. This report does not constitute a standard, specification or regulation. The authors would like to acknowledge the assistance of the following members of the technical review panel for ICT-R27-8: Scott Lackey, Laura Shanley, Thomas Zehr and Patricia Broers. The authors would also like to acknowledge the assistance of David Lippert in preparing and distributing the questionnaire. The assistance of I. Al-qadi of the University of illinois, P. Lum of the LAfarge Group, and personnel at Iowa Dot, Kansas Dot, Michigan Dot and Ohio Dot is greatly appreciated.