Proposed Method to Determine the Flow Number from Laboratory Axial Repeated Loading Tests in Bituminous Mixtures

Several research efforts have found the number of cycles corresponding to the lower strain rate in a repeated permanent deformation test, known as flow number (FN), to be a good asphalt mix stability indicator; however, its variability has limited its implementation. Current procedures for calculating FN rely on data smoothing techniques, which can yield very different values for the same specimen if different moving average periods (MAPs) are used. A new methodology for determining the flow number is proposed, by modeling the permanent strain vs. load cycles curve as a continuous function, and determining its value using an explicit equation. To validate the procedure, permanent deformation data from tests performed on 10 cold mix replicate samples were analyzed. Comparison between the flow numbers determined with the proposed explicit form and current data smoothing procedures (using varying MAP values) indicate that while there is no statistical difference between the mean FN determined using either method, a substantial reduction in variability can be achieved by using the proposed methodology. Use of the flow number estimated with the proposed method to select the data for estimation of the power model parameters was also evaluated. The results indicate that using such flow number as an upper cut off-point of the data used to fit the power model produces a slight reduction in the variability of its estimated parameters. Adoption of the proposed model could be useful for permanent deformation characterization purposes and as a unifying criterion for selecting the data used for that purpose.

Language

  • English

Media Info

  • Media Type: CD-ROM
  • Features: Figures; References; Tables;
  • Pagination: 17p
  • Monograph Title: TRB 86th Annual Meeting Compendium of Papers CD-ROM

Subject/Index Terms

Filing Info

  • Accession Number: 01044205
  • Record Type: Publication
  • Report/Paper Numbers: 07-1901
  • Files: TRIS, TRB
  • Created Date: Feb 8 2007 6:36PM