This report contains the results of a literature survey and small computer study using the ELSYM 5 computer program to investigate the state of stresses and strains in asphalt mixtures used as overlays as compared to those used in conventional pavement layers. Results from the literature survey indicate that very thin overlays on old flexible pavements should probably be avoided since the tensile stresses between dual tires are very high, in fact, several of the overlay design procedures avoid thicknesses of less than 3 inches because of the high tensile stress state in the overlays. As the overlay thickness increases beyond 3 inches the stresses decrease and fatigue cracking problems become less severe. However, overlays on rigid pavements appear to fail either by permanent deformation due to repeated loads or stripping or cracking caused by reflection of underlying cracks. The use of elastic layered theory to study the shear stresses in overlays on rigid pavements showed that shear stresses decreased with increase in stiffness of the underlying layer. However, as the modulus of the overlay decreased these shear stresses increased dramatically, such is probably the case when low density or moisture damage is sustained by the overlay. Results of this study indicate that there are mixture design questions that should be considered further including the effects of low density and moisture damage on the stability and permanent deformation characteristics of overlay mixtures. (FHWA)

  • Supplemental Notes:
    • Study conducted in cooperation with the Federal Highway Administration Research Study title: Mixture Design for ACP Overlays.
  • Corporate Authors:

    University of Texas, Austin

    Center for Transportation Research, 3208 Red River Street
    Austin, TX  United States  78705

    Texas State Department of Highways & Public Transportation

    Transportation Planning Division, P.O. Box 5051
    Austin, TX  United States  78763

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Authors:
    • Roberts, F L
    • Kennedy, T W
  • Publication Date: 1984-2

Media Info

  • Pagination: 32 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00392219
  • Record Type: Publication
  • Report/Paper Numbers: FHWA-TA-84-13+318-1 Final Rpt.
  • Contract Numbers: 3-9-82-318
  • Created Date: Feb 28 1985 12:00AM