EFFECT OF EQUIPMENT AND MIX VARIABLES ON SURFACE SHADOWS IN ASPHALT CONCRETE MATS. FINAL REPORT

Surface irregularities causing a rough ride on an asphalt concrete pavement may be contributable to equipment related problems as well as to mix related problems. Problems relating to the laydown equipment can cause such irregularities as surface waves, ripples, tearing of the mat, screed marks, nonuniform texture and surface shadows. Surface shadows can be defined as areas of discoloration on the surface of the mat. In the past the surface shadows have been called auger shadows as they were thought to be related to overloading the augers on the paver with the asphalt concrete mix -- burying the augers. This study presents a discussion of the mixture variables as well as equipment variables which influence the presence and severity of surface shadows. The problem of surface shadows exists throughout the state of Texas. It is not restricted to any one type of mix, although mixture properties do influence the development of the phenomenon. A study of 11 hot mix projects in District 2 of the Texas State Department of Highways and Public Transportation is presented. This study examines equipment, construction and equipment variables. Based on the results of the study of the 11 selected projects in District 2, a field construction investigation was accomplished to create surface shadows "on demand" by varying selected parameters related to the paver and the paver operation. The field test project consisted of operations at three sites within Texas. The results of this evaluation are presented and analyzed. Suggestions are made by which to prevent or decrease the intensity and frequency of surface shadows based on the results of the field evaluation.

  • Supplemental Notes:
    • Research study title: Effect of Mix Design and Equipment on Workability and Rideability of ACP.
  • Corporate Authors:

    Texas Transportation Institute

    Texas A&M University System, 1600 E Lamar Boulevard
    Arlington, TX  United States  76011

    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:
    • Scherocman, J A
    • Rodriguez, M A
    • Little, D N
  • Publication Date: 1990-11

Media Info

  • Features: Appendices; Figures; Photos; References; Tables;
  • Pagination: 203 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00616399
  • Record Type: Publication
  • Report/Paper Numbers: FHWA/TX-89/1134-1F, Res Rept 1134-1F, TTI: 2-8-89/9-1134
  • Contract Numbers: Study 2-8-89/9-1134
  • Files: TRIS, USDOT, STATEDOT
  • Created Date: Oct 31 1991 12:00AM