Precision Assessment of the Modified Wheel Tracking Device Based on Small-Scale Testing of New Zealand Hot Mix Asphalt
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The Wheel Tracking Device (WTD) has been widely used for laboratory characterisation of permanent deformation or rutting in Hot Mix Asphalt (HMA), however, the conventional setup of the device has limitations in terms of capturing the tertiary zone of the permanent deformation curve, and subsequently, the Flow Number (FN). This makes the Hot Mix Asphalt (HMA) characteristics related to the permanent deformation resistance difficult to analyse. Hence, a newly modified setup of WTD has been proposed for better characterisation of HMA mixes. The study focuses on the investigation of the repeatability of the new test-setup to eliminate any arbitrary calculations. The study utilised three different kinds of mixes with Nominal Maximum Aggregate Size (NMAS), and Void in Total Mix (VTM) as the factors, each with three replicates. For the experimental part and analysis, both confined and unconfined setup of the device will be used for each kind of mix. For the unconfined setup, the Flow Number (FN) was used as the parameter for the analysis. For the confined setup, the rut depths at 12000, 25000, and 50000 wheel passes or the final rut depth were utilised. This study is expected to give an insight to the modified Wheel Tracking Device and its repeatability for the purpose of robust characterisation of asphalt concrete mixes, which will in turn be helpful in developing precision estimates required for making it a standard practice in the near future.
KeywordsPermanent deformation Wheel Tracking Device (WTD) Precision Hot Mix Asphalt (HMA)
The authors would like to acknowledge the staff from Fulton Hogan in Christchurch for supplying the materials utilised in this study. The authors also owe considerable thanks to the colleagues at the University of Canterbury, Christchurch, New Zealand, especially the ones in Pavement Research wing. Mr. John Kooloos, the technical officer of the Pavement Research Laboratory is particularly acknowledged for his constant help in the production of the samples, and also for useful advices.
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