Measured and Predicted Performance Impacts from Reduced Design Gyrations

The effect of reduced gyration levels on mix design and performance was quantified in this study. Changes in fatigue resistance and rutting resistance when design gyrations were decreased using different approaches were captured in laboratory tests. Using four separate mixtures, a standard 75 gyration design, a reduced 65 gyration design meeting standard volumetrics using additional binder, and a reduced 65 gyration design where standard volumetrics were met by adjusting the fine aggregate gradation rather than through the addition of binder, three various were studied. Using a suite of laboratory tests, the properties of the various mix designs were evaluated. Laboratory tests included the following: fatigue resistance, rutting resistance, and dynamic modulus. Using the shear response measured during gyratory compaction, compactability was assessed. Reducing gyrations and adjusting the fine aggregate gradation increased the average modulus, as shown in laboratory tests, and the average modulus decreased at lower gyrations when binder was increased. The same trend as dynamic modulus where adjusted fine aggregate gradations increased average resistance to permanent deformation was yielded by flow number tests, and added binder decreased average resistance to permanent deformation relative to the standard, reference mix design. Nonetheless, the inherent variability of the lab tests could not be overcome by the trends in the average modulus and permanent deformation responses, and the differences were largely insignificant. Both types of reduced design gyrations improved the compactability relative to the reference mix with higher design gyration, as indicated by the Compaction Force Index computed from the gyratory shear resistance. It is implied by this study that lowering design gyrations by a moderate level can, but not always, be used to achieve more compactable and more crack resistant mixtures without jeopardizing rutting resistance in a significant way. However, it is crucial to note that performance tests need to be completed due to the fact that a general or consistent rule does not apply. The reduced gyration level negatively affected some mixtures in the study. Due to the particulars of local materials, laboratory performance tests which can be conducted with an Asphalt Mixture Performance Tester are recommended for guidance.

Language

  • English

Media Info

  • Media Type: Print
  • Features: Appendices; Figures; Photos; References; Tables;
  • Pagination: pp 337-367
  • Monograph Title: Asphalt Paving Technology 2012
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 01523189
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Apr 9 2014 8:37PM