Laboratory Evaluation of Long-Term Draindown of Porous Asphalt Mixtures

Long-term draindown is the term adopted in this study to describe the downward flow of binder in a porous asphalt mixture due to the force of gravity at high temperatures experienced during service, especially in warmer climates. The concept of long-term draindown has been qualitatively noted in field observations of porous asphalt mixtures including open graded friction courses (OGFC). This research quantified the long-term draindown of three different OGFC mixtures by measuring the permeability of the mixes throughout an 84-day conditioning period at 140°F (60°C). The results showed that the permeability of all three mixtures decreased over the first 56-days and then leveled off for the remaining 28-days. The permeability data was used to calculate the rate of permeability loss over the initial 56-day period for each mix. To verify that the permeability reduction was due to binder draindown, the distribution of binder content of randomly selected specimens was measured. The results from this study indicated that cellulose fibers did not have any influence on the long-term draindown of the mixtures evaluated. Also, the mixture made with a ground tire rubber (GTR) modified binder exhibited a lower rate of permeability loss compared to the other two mixtures made with an SBS modified binder. Finally, one of the mixes evaluated was produced as a warm mix OGFC using Evotherm™ 3G and its long-term draindown potential was similar to the control mix even though this mix did not contain fibers and it had a similar binder content as the other mixes.

• Supplemental Notes:
  • This paper was sponsored by TRB committee AFK40 Characteristics of Asphalt-Aggregate Combinations to Meet Surface Requirements.
• Corporate Authors:

  Transportation Research Board

  500 Fifth Street, NW
  Washington, DC  United States  20001
• Authors:
  • Putman, Bradley J
  • Lyons, Kimberly R
• Conference:
  • Transportation Research Board 93rd Annual Meeting
  • Location: Washington DC
  • Date: 2014-1-12 to 2014-1-16
• Date: 2014

Language

• English

Media Info

• Media Type: Digital/other
• Features: Figures; References; Tables;
• Pagination: 14p
• Monograph Title: TRB 93rd Annual Meeting Compendium of Papers

Subject/Index Terms

• TRT Terms: Asphalt mixtures; Binder content; Gravity; High temperature; Laboratory tests; Permeability; Porous materials
• Identifier Terms: Evotherm
• Uncontrolled Terms: Draindown
• Subject Areas: Highways; Materials; I30: Materials;

Filing Info

• Accession Number: 01514842
• Record Type: Publication
• Report/Paper Numbers: 14-1484
• Files: TRIS, TRB, ATRI
• Created Date: Feb 21 2014 3:16PM