Rutting Evaluation of Lopke Aggregate Blends

Superpave’s current requirements for coarse aggregate angularity require 100% one and two fractured faces, determined according to ASTM D5821, for design traffic levels greater than 30 million equivalent single axle loads (ESAL). These limits are based on the consensus of a panel of experts determined using a modified Delphi process and not based on testing conducted as part of the Strategic Highway Research Program (7). These criteria effectively exclude most gravel sources from being used in pavements with in excess of 30 million design ESAL. This study evaluated the rutting performance of three levels of coarse aggregate angularity: as-received, 95% two crushed faces and 100% two crushed faces. Testing was conducted on a currently approved 12.5 mm nominal maximum aggregate size (NMAS) and a 25.0 mm NMAS Superpave mix using a crushed gravel source produced by Lopke Contracting in New York State. The existing mix designs were verified with Lopke’s as-received crushed gravel. Mix designs using the same gradation and fine aggregate fraction were conducted with Lopke crushed gravel having in excess of 95% two fractured faces (100% one fractured face) and a 100% two face crushed limestone source. All six mixtures met the Superpave mix design criteria for greater than 30 million ESAL. One exception was the dust to effective binder content for the 25 mm NMAS limestone, which exceeded the criteria by 0.1. Rut testing was performed using the asphalt pavement analyzer (APA) at the optimum asphalt content indicated for each mixture. The rut testing was performed using the protocol recommended by National Cooperative Highway Research Program (NCHRP) 9-17, “Accelerated Laboratory Rutting Tests: Asphalt Pavement Analyzer.” The test protocol from NCHRP 9-17 used to rut test the mixes is more severe than the protocol used by most states currently employing the Asphalt Pavement Analyzer (APA) due to the higher vertical load and pressure. The NCHRP 9-17 criteria were developed for surface mixes. Since stresses are less deeper in the pavement structure, these criteria are more restrictive than need be for the 25.0 mm NMAS mixes. However, all of the mixes performed better than the rutting criteria (4.5 mm) recommended by NCHRP 9-17 for greater than 30 million ESAL. Statistically, the rut depth results from Lopke’s as-received material were not different from a 100% crushed limestone material for either the 12.5 or 25.0 mm NMAS mixes. Based on the testing conducted in this study, Lopke’s crushed gravel, either as-received or with 95% two crushed faces, may be used to design mixes that will provide the same rutting performance as a 100% two face crushed limestone source for traffic levels greater than 30 million design ESAL.

• Record URL:
  • http://www.eng.auburn.edu/research/centers/ncat/files/reports/2003/rep03-06.pdf
• 
• Corporate Authors:

  National Center for Asphalt Technology

  Auburn University, 277 Technology Parkway
  Auburn, AL  United States  36830

  Lopke (FS) Contracting, Incorporated

  Apalachin, NY  United States 
• Authors:
  • Prowell, Brian D
• Publication Date: 2003-8

Language

• English

Media Info

• Media Type: Web
• Features: Appendices; References; Tables;
• Pagination: 28p

Subject/Index Terms

• TRT Terms: Aggregate gradation; Angularity; Asphalt content; Binder content; Blends; Coarse aggregates; Crushed limestone; Equivalent single axle loads; Fine aggregates; Mix design; Pavements; Rutting; Superpave; Traffic
• Identifier Terms: Asphalt Pavement Analyzer; National Cooperative Highway Research Program
• Uncontrolled Terms: Crushed gravel
• Subject Areas: Geotechnology; Highways; Operations and Traffic Management; Pavements; I36: Aggregates;

Filing Info

• Accession Number: 01031580
• Record Type: Publication
• Report/Paper Numbers: NCAT Report 03-06
• Files: TRIS
• Created Date: Aug 23 2006 4:06PM