NATIONAL POOLED FUND STUDY NO. 176: VALIDATION OF SHRP ASPHALT MIXTURE SPECIFICATIONS USING ACCELERATED TESTING

This study was initiated in 1997 and incorporated two phases. The purpose of Phase I was to evaluate the sensitivity of tests to changes in certain factors within the framework of the Superpave specifications. The purpose of Phase II was to provide data for analysis of the effects of the primary factors of the study. The overall objectives of this study were to validate various Hot Mix Asphalt (HMA) aggregate specifications and volumetric relationships established by Superpave. Specifically, the study addressed the effects of voids in mineral aggregate (VMA), fine aggregate angularity (FAA), and HMA mixture gradation on the rutting performance of mixtures designed in accordance with the Superpave volumetric mixture design procedure (N-design of 96). Mixture designs were conducted using a single neat PG64-22 binder, two nominal maximum aggregate sizes (19 and 9.5 mm), two coarse aggregate types (limestone and granite), three fine aggregate types possessing FAA values of 39, 44, and 50, and three gradation types (above, through, and below the restricted zone). The rutting performance of the mixtures were evaluated using the Indiana Department of Transportation (INDOT)/Purdue Accelerated Pavement Test Facility (APT), the Purdue Laboratory Wheel Track Test Device (PURWheel), and the Superpave Shear Tester (SST). In addition, triaxial testing was utilized to identify critical VMA. Test results indicate that APT, PURWheel, SST, and triaxial test are sensitive to material property changes. The observed VMA associated with rutting was higher than the Superpave minimum VMA requirements. VMA could not be correlated with performance data. Film thickness was identified as a robust mixture property that correlated better with rutting performance than traditional volumetric properties. Fine aggregate angularity was found to correlate with performance, but incorporating very high fine aggregate angularity did not necessarily provide better performance. Gradation influences APT, PURWheel, SST, and triaxial test results. However, the restricted zone may not be adequate to characterize gradation to ensure acceptable performance. The asphalt binder content corresponding to optimum triaxial strength and PURWheel rutting performance ranged from 0.0 to 0.5% less than the Superpave design asphalt binder content for most mixtures. Based on all test results and analyses, it is suggested that film thickness be included in mixture design procedures with an acceptable range of 7 to 9 microns. Stringent VMA criteria are not suggested because many factors can impact VMA process, such as asphalt binder content and density. These factors could deceive the essence of VMA as a durability or HMA structure parameter. The use of a typical value of FAA (45) is suggested for acceptable rutting performance. The mixture design and performance data suggest that achieving 4.0% air voids when using high FAA (50) blends can lead to excess asphalt and thus poor rutting performance. The selection of gradation with respect to the Superpave restricted zone as a requirement for performance is not suggested.

  • Record URL:
  • Corporate Authors:

    Purdue University/Indiana Department of Transportation JHRP

    Purdue University, School of Civil Engineering
    West Lafayette, IN  United States  47907-1284

    Indiana Department of Transportation

    100 N Senate Avenue
    Indianapolis, IN  United States  46204

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Authors:
    • Stiady, J L
    • Hand, AJT
    • Noureldin, A S
    • Galal, K
    • Hua, J
    • White, T D
  • Publication Date: 2003-2

Language

  • English

Media Info

  • Features: Appendices; Figures; Photos; References; Tables;
  • Pagination: 571 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00964788
  • Record Type: Publication
  • Report/Paper Numbers: FHWA/IN/JTRP-2003/02,, Final Report
  • Contract Numbers: SPR-0002
  • Files: TRIS, USDOT, STATEDOT
  • Created Date: Oct 3 2003 12:00AM