Selection of overlay thickness is dependent on site conditions and is used with knowledge of relative asphalt concrete toughness in order to develop a specific fatigue cracking performance life. In this study, a procedure is developed and the results are shown for a mechanistic approach to the prediction of fatigue cracking in asphalt concrete overlays. The procedure consists of (1) establishment of field variables, (2) use of a pavement layer computer program to determine strains in predetermined increments of overlay depth, (3) establishment of overlay basic fatigue life equation based on relative asphalt concrete toughness predicted from resilient modulus and indirect tensile strength tests on laboratory specimens of overlay mixture, (4) application of cumulative damage theory (Miner's rule) for each overlay increment with a predetermined seasonal relationship in order to "model" semi-controlled fatigue cracking progression from bottom-most overlay increment to surface of overlay, (5) calculation of cumulative 18 kip ESAL when fatigue cracking reaches overlay surface, (6) addition of further 18 kip ESAL to cause pavement roughness near terminal serviceability, and (7) use of total ESAL as an estimated fatigue cracking performance life to assist in selection of overlay thickness. Results indicate that the performance life is mainly proportional to overlay thickness and to lack of cracking and faulting of the existing (old) asphalt concrete surface. Implication is that a good correlation is needed between cracking condition of the existing asphalt concrete surface and its "slab-modulus" analog for computer program overlay strain calculation. This can be an objective of a pavement management program. The soil modulus was found to have negligible effect for the range of site variables and for the incremental overlay cracking procedure used. The estimated fatigue cracking performance lives (total ESAL) are approximately 7 times those lives corresponding to the method of spontaneous fatigue cracking up through the overlay when the bottom-most overlay cracks. This indicates that the total ESAL predicted by the procedure in this study should not require the use of a "field factor" multiplication constant that has been conventionally used in the past. Numerical examples are shown in the report for selecting overlay thickness to resist fatigue cracking. These examples incorporate site variables, ESAL rate from traffic analysis and design years of performance.

  • Corporate Authors:

    University of Idaho, Moscow

    Department of Civil Engineering
    P.O. Box 441022
    Moscow, ID  United States  83844-1022

    Idaho Transportation Department

    3311 W State Street, P. O. Box 7129
    Boise, ID  United States  83707-1129
  • Authors:
    • Lottman, R P
    • Brejc, S
  • Publication Date: 1991-6-30


  • English

Media Info

  • Features: Appendices; Figures; Tables;
  • Pagination: 61 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00624949
  • Record Type: Publication
  • Report/Paper Numbers: UI Project 128-K439
  • Contract Numbers: ITD Grant 91-21
  • Created Date: Sep 17 1993 12:00AM