Multiaxial Strain Response of Asphalt Concrete Measured During Flow Number Performance Test

This research developed a more complete understanding of the mechanics of asphalt concrete permanent deformation such that future methodologies for materials characterization and rutting performance prediction are guided by these principles. Currently, the Asphalt Mixture Performance Tester (AMPT) formerly known as the Simple Performance Tester (SPT) and corresponding Flow Number test are well poised to impact the state-of-the-practice. Salient aspects of the test and phenomena associated with rutting were reviewed. A mechanistic methodology was followed to determine relevant multiaxial stresses associated with rutting. In addition, a noncontact image-based strain measurement technique was developed to provide the radial and axial strain occurring during the test. Multiaxial strains measured under the application of two complementary stress states provided additional insight into the three dimensional mechanics of permanent strain growth in asphalt concrete. A single parameter like the Flow Number cannot provide this information. There are no guarantees that the Flow Number will be encountered in all mixtures and tests. The multiaxial characterization clearly shows that asphalt concrete mixtures can and do volumetrically compress or volumetrically dilate depending on stress state and density, sometimes before and after tertiary flow is achieved. Concepts of permanent strain path and permanent strain trajectory are utilized as a means to more clearly separate the contribution of binder apart from the contribution of aggregate on permanent deformations. Two distinctive sets of mixtures; one having measured rutting from an accelerated pavement test and the other having a broader variation in air void content and aggregate gradation were utilized to explore these concepts.

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  • English

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  • Accession Number: 01158653
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Jun 11 2010 12:05PM