OPEN-GRADED ASPHALT FRICTION COURSES

The open-graded friction course, which consists of a high-void, hot asphalt plant mix that permits rapid drainage of rainwater (through the course and out to the shoulder), is characterized by a large percentage of one-sized coarse aggregate to ensure a minimum of 15 percent air voids. Details are outlined of the mix composition and it is recommended that the amount passing the no. 8 sieve does not exceed 15 percent and the amount retained between the no. 4 and the 3/8 in. sieves is at least 40 percent. The addition of mineral filler is recommended, and suggested aggregate gradation and aspahlt content range are tabulted. The mineral aggregate must be resistant to polishing and can be any sound crushed aggregate having an abrasion loss of less than 45 percent. Recommendations for grades of asphalt cement are presented, and asphalt content selection is discussed. Laboratory tests should be conducted to determine the need for an additive. The preparation of the existing surface involves repairs, leveling, and the application of a tack coat. The mixing temperature is between 225 deg F and 250 def F. The mix should be transported to the job site in clean vehicles with smooth dump beds that have been sprayed with a nonpetroleum release agent. The importance is stressed of placing the mix in an appropriate ambient temperature and on a surface sufficiently warm to minimize the risk of excessive cooling before completion of rolling. For compaction, one or two coverages with a steel-wheeled roller weighing not more than 10 tons is sufficient.

• Corporate Authors:

  Asphalt Institute

  2696 Research Park Drive
  Lexington, KY  United States  40511-8480
• Publication Date: 1974-11

Media Info

• Features: Figures; Tables;
• Pagination: 4 p.

Subject/Index Terms

• TRT Terms: Asphalt; Asphalt cement; Coarse aggregates; Drainage; Friction; Mineral fillers; Mixing; Open graded aggregates; Temperature
• Old TRIS Terms: Mixing temperature
• Subject Areas: Highways; Hydraulics and Hydrology; Materials; Pavements;

Filing Info

• Accession Number: 00083683
• Record Type: Publication
• Report/Paper Numbers: CL-10
• Files: TRIS
• Created Date: Apr 22 1975 12:00AM