Because a widely accepted laboratory durability test for asphalt does not exist, many agencies including the Pennsylvania Department of Transportation (DOT) have resorted to controlled field experiments to evaluate and characterize those physical properties of the asphalt binder that are associated with aging and their relationship to pavement performance. Three asphalt durability projects undertaken by the Pennsylvania DOT are summarized in this paper: 1961-1962 test pavements, 1964 test pavements, and 1976 test pavements. The study was limited to the evaluation of dense-graded asphaltic concrete wearing courses in which a different asphalt source or type was used. Except for the 1961-1962 test pavements, the only significant variable was the asphalt type. Mix composition and construction techniques were held reasonably constant. After construction, periodical core samples were obtained from these pavements to determine the percentage of air voids and the rheological properties of the aged asphalts. It has been observed that aging of the pavements results in progressively lower penetration and higher viscosity, which exhibit a hyperbolic function with time. However, the accompanying decrease in low-temperature ductility after the penetration falls below 30, and the rate of gain in shear susceptibility relative to increase in viscosity at 77ousF, have been found to be important factors that affect the pavement performance. Lower ductility values were associated with a higher incidence of load-associated longitudinal cracking. High stiffness modulus of the asphalt cement at low temperatures and a 20,000-sec loading time contributed to nonload-associated transverse cracking. In the discussion, Davis notes that his own experience supports the authors contentions and he proposes that the ductility test could serve as a viscometer if stress levels were recorded.

Media Info

  • Media Type: Print
  • Features: Figures; References; Tables;
  • Pagination: pp 41-50
  • Monograph Title: The asphalt triangle: supply, demand, and technology; and asphalt durability
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00450694
  • Record Type: Publication
  • ISBN: 0309038081
  • Files: TRIS, TRB
  • Created Date: Feb 28 1986 12:00AM