The objective of this investigation was to determine the validity of using a linear viscoelastic constitutive equation to characterize asphalt concrete in the design of pavement systems. The investigation was conducted in two phases. In the first phase, creep tests in compression, tension and torsion, and repeated loading tests were performed on cylindrical specimens of asphalt concrete for various axial loads at different confining pressures and different temperatures to determine the response functions, and establish the degree of linearity and evaluate the time-temperature equivalence of the response. On the basis of these tests creep functions and complex modulus values for the asphalt concrete were determined. The second phase of the investigation was conducted to check if the characterization of the asphalt concrete obtained in the first phase of the program could be used to predict the behaviour of asphalt concrete under stress states which are similar to those that might exist in actual pavements by testing beams and slabs and a Winkler foundation. In this paper only the results of the first phase of the investigation are presented and discussed. It was found that the type of test (e.g. uniaxial, triaxial, torsion) influences the magnitude and nature of the viscoelastic functions. For one type of test, the results obtained are consistent. Based on the results of tests under hydrostatic stress states it was observed that the samples exhibited a substantial degree of anisotropy. It is hypothesized that this is due to the method of compaction utilized in preparation of the samples. It was also observed that the volumetric response of asphalt concrete was time dependent and that the usual assumption of incompressibility was questionble. Thermortheological simplicity was found to be a satisfactory assumption for uniaxial compression tests. In order to reduce the influence of stress level, stress state, anisotropy and other effects to a level that will make linear isotropic viscoelasticity an acceptable characterization of asphalt concrete, it has been suggested that a limit be placed on the strain level that can occur in the asphalt concrete. This was done using the experimental data on the basis of a subjective evaluation. It is strongly recommended that sensitivity studies on the basis of pavement performance be conducted to determine the acceptable variations for ideal material characteristics and hence establish the degree of refinement required in the characterization of materials for the design of pavement systems. /AUTHOR/

  • Supplemental Notes:
    • Presented at the Third International Conference on the Structural Design of Asphalt Pavements, Grosvenor House, Park Lane, London, England, Sept. 11-15, 1972.
  • Corporate Authors:

    International Conf Struct Design Asph Pvmts (3rd)

    University of Michigan, Department of Civil Engineering
    Ann Arbor, MI  United States  48104

    International Conf Struct Design Asph Pvmts (3rd)

    University of Michigan, Department of Divil Engineering
    Ann Arbor, MI  United States  48104

    Interrational Conf Struct Design Asph Pvmts (3rd)

    University of Michigan, Department of Civil Engineering
    Ann Arbor, MI  United States  48104
  • Authors:
    • Nair, K
    • Smith, W S
    • Chang, C
  • Conference:
  • Publication Date: 1972-9

Media Info

  • Features: Figures; References; Tables;
  • Pagination: p. 277-289
  • Serial:
    • Volume: 1

Subject/Index Terms

Filing Info

  • Accession Number: 00261956
  • Record Type: Publication
  • Report/Paper Numbers: Proceeding
  • Files: TRIS
  • Created Date: Oct 22 1974 12:00AM