Open-Graded Wearing Courses in the Pacific Northwest

The Oregon Department of Transportation (ODOT) has been placing ¾-inch nominal maximum aggregate size (NMAS) open-graded wearing courses (OGWCs) in structural layers of two inches or more for about 30 years. Despite this, OGWC performance in the Pacific Northwest is not well understood. This study determines the use and performance of ODOT OGWCs with special attention given to ¾-inch open-graded HMA (previously referred to as “F-Mix”) and recommends guidelines for the future use of OGWCs. The best estimated service life of ODOT ¾-inch open-graded HMA ranges from 14 years (< 5,000 ADT) down to 7 years (> 100,000 ADT), which is less than comparable dense-graded mixes. The primary mode of distress is raveling and studded tire wear. Reduced service life, along with uncertain and unquantified safety benefits and a possible greater risk of early failure lead to a recommendation to discontinue use of ¾-inch open-graded HMA in Oregon as a standard surface mix. OGWCs used elsewhere in the U.S. are not likely suited for ODOT use due to their susceptibility to studded tire wear and are not recommended for adoption. If ¾-inch open-graded HMA does continue in use, recommendations are: (1) quantify its benefits, (2) restrict its use to low traffic (< 30,000 ADT), (3) recalibrate PMS expected life to be more in line with observed historical life, and (4) require the use of a windrow pick-up machine or end-dump transfer machine when paving OGWC.

• 
• Record URL:
  https://rosap.ntl.bts.gov/view/dot/22910
• Corporate Authors:

  University of Washington, Seattle

  Civil and Environmental Engineering Department
  201 More Hall, Box 352700
  Seattle, WA  United States  98195-2700

  Oregon Department of Transportation

  Research Section, 200 Hawthorne Avenue, SE, Suite B-240
  Salem, OR  United States  97301-5192

  Federal Highway Administration

  1200 New Jersey Avenue, SE
  Washington, DC  United States  20590
• Authors:
  • Muench, Stephen T
  • Weiland, Craig
  • Hatfield, Joshua
  • Wallace, Logan K
• Publication Date: 2011-6

Language

• English

Media Info

• Media Type: Web
• Edition: Final Report
• Features: Appendices; Figures; References; Tables;
• Pagination: 134p

Subject/Index Terms

• TRT Terms: Hot mix asphalt; Open graded aggregates; Pavement distress; Pavement performance; Service life; Wearing course (Pavements)
• Geographic Terms: Oregon; Pacific Northwest
• Subject Areas: Construction; Highways; Pavements; I52: Construction of Pavements and Surfacings;

Filing Info

• Accession Number: 01354135
• Record Type: Publication
• Report/Paper Numbers: FHWA-OR-RD-17
• Contract Numbers: SPR 680
• Files: TRIS, USDOT, STATEDOT
• Created Date: Oct 19 2011 12:53PM