Compaction and Tenderness of HMA Mixtures: A Laboratory Study

This study evaluates the influence of binder viscosity, compaction temperature, compaction pressure, and binder content upon the densification of asphalt test mixtures produced using Process Modified Asphalt (PrMA) and Polymer Modified Asphalt (PMA). The effects upon densification are evaluated through a two stage laboratory study. The first stage is concerned with comparing the effort needed to compact each mix using two compaction levels and three compaction temperatures. One type of aggregate and one type of mix gradation are used in this evaluation. The second stage is concerned with the effect of the binder content on the mixtures? resistance to compaction and densification while varying the compaction temperatures, and pressure for mixtures made with the two types of binders tested. The results of the first stage showed that mixes vary in their sensitivity to the compaction level and the compaction temperature. It is observed that there is a high level of interaction between compaction pressure and temperature. Surprisingly, the conventional thinking of ?density always increases with temperature? does not apply for all mixtures. There are clearly optimum temperature and pressure ranges within which densification can be achieved more efficiently. The second stage showed that the behavior of under asphalted mixtures depend mainly on the type of binder used. While for the over asphalted mixtures, their behavior is identical regardless of compaction temperature, pressure or binder type. While some studies have reported on what are known as ?Tender Zones,? very few could quantify this in the laboratory and report on what makes a mixture tender and how to give guidelines to contractors to avoid tender zones. The authors suggest that these zones could be asphalt binder specific and should be defined in a 3-domain chart showing pressure, temperature sensitivity, and asphalt binder type and content in the mixture.

Language

  • English

Media Info

  • Media Type: CD-ROM
  • Features: Figures; References; Tables;
  • Pagination: 19p
  • Monograph Title: TRB 86th Annual Meeting Compendium of Papers CD-ROM

Subject/Index Terms

Filing Info

  • Accession Number: 01044577
  • Record Type: Publication
  • Report/Paper Numbers: 07-1007
  • Files: TRIS, TRB
  • Created Date: Feb 8 2007 5:36PM