EFFECT OF FILM THICKNESS, VOIDS AND PERMEABILITY ON ASPHALT HARDENING IN ASPHALT MIXTURES

Laboratory experiments were conducted on asphaltic mixtures to study the effect of asphalt film thickness, voids and permeability on asphalt hardening. Limestone aggregate and a 200-250 penetration grade asphalt were used in the study. Specimens of both single-size and graded mixtures were prepared using gyratory compaction. The specimens were then subjected to permeability measurements followed by alternate cycles of accelerated oxidation and creep testing. After the oxidation and testing cycles, present accessible void measurements were made for each specimen. The accessible voids were measured using four different techniques; 24-hour soaking, hand pumping, under vaccum (absolute pressure 10 cm. mercury) and under vaccum (absolute pressure 2.5 cm. mercury). Finally, the asphalt was recovered from each specimen and its penetration determined. Before asphalt recovery, however, each specimen was subjected to a final creep test. The results, based on statistical analysis, indicated that for single-sizing mixtures the ratio of film thickness factor to permeability is the best predictor of mixture's resistance to hardening caused by accelerated oxidation. For graded mixtures, the asphalt film thickness concept breaks down and permeability alone was found to be the best predictor of a mixture's resistance to hardening. The results show that permeability is related to the entire void system of graded asphaltic mixtures. Straight line relationships were observed between the log of permeability and voids. Since permeability was found to be closely related to the accessible air voids (hand pumping), the measurement of percent accessible air voids (hand pumping) can be substituted for permeability as a predictor of mixture resistance to hardening in graded mixtures. A comparison between the penetration test results of the recovered asphalt from asphaltic mixtures and their corresponding creep test results indicates that the creep test may be used as a measure of asphalt hardening. Therefore, this test can be employed as a nondestructive test to measure progressive asphalt hardening in asphaltic mixtures. The devised durability test was evaluated and was found to be a good laboratory procedure for evaluation of asphalt hardening in asphaltic mixtures.

  • Corporate Authors:

    Purdue University/Indiana Department of Transportation JHRP

    Purdue University, School of Civil Engineering
    West Lafayette, IN  USA  47907-1284
  • Authors:
    • KUMAR, A
  • Publication Date: 1976-6-23

Media Info

  • Features: Appendices; Figures; References; Tables;
  • Pagination: 165 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00141542
  • Record Type: Publication
  • Report/Paper Numbers: JHRP-76-19 Final Rpt.
  • Files: TRIS, ATRI
  • Created Date: Nov 17 1976 12:00AM