BEHAVIOR OF BITUMINOUS ROADBASE MATERIALS UNDER REPEATED LOADING

In an effort to asses the effect of slow moving heavy commercial vehicles with high axle loads on flexible pavement structures, the behavior was studied of 4 bituminous roadbase materials subjected to low frequency repeated loadings. Tests were performed on specimens of dense macadam consisting of 1 in. maximum size continuously graded crushed rock aggregate with 4.0 percent of either 100 pen. or 200 pen. bitumen or 4.55 percent of a 54 e.v.t. tar binder. Also tested was a gap graded rolled asphalt mix made with the same rock coarse aggregate and sand with 5.7 percent of 45 pen. bitumen as binder. Under repeated strain controlled loading, the stiffness of all 4 materials fell progressively to beyond the value of 60 percent of the initial stiffness at which most tests were determined. The service lives of the dense bitumen macadams were independent of test temperatures over the range 0 c. + 40 c., and also independent of the grade of bitumen used. The service life of the rolled asphalt mix was also unaffected by temperature but was longer than the dense macadam at a given strain level. The dense tar macadam having the same volume of binder as the bitumen macadam gave shorter service lives, but the lives at +30 c. and +40 c. were longer than at 0 c. Mathematical expressions are utilized to represent the relationship between the percentage drop in stiffness, and the repetitions of loading at the strain level (epsilon). The progressive reductions in stiffness were generally unaccompanied by visual cracking and were partially recoverable during periods of rest. The mathematical expressions described (above) were used in conjunction with elastic layered theory for the analysis of typical pavement structures under the action of slow moving high axle loads at high ambient temperature. The results indicate significant differences in performance between the materials which should be recognized in rational structural design.

  • Supplemental Notes:
    • Proceedings of the meeting held in Houston, Texas, February 1973.
  • Corporate Authors:

    University of Minnesota, Minneapolis

    155 Experimental Engineering Building
    Minneapolis, MN  United States  55455
  • Authors:
    • Pell, P S
    • Hanson, J M
  • Conference:
  • Publication Date: 1973

Media Info

  • Features: Figures; References; Tables;
  • Pagination: p. 200-229
  • Serial:
    • Volume: 42

Subject/Index Terms

Filing Info

  • Accession Number: 00127329
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Dec 16 1975 12:00AM