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Recommendations for Reducing Superpave Compaction Effort to Improve Mixture Durability and Fatigue Performance

File Language:
English


Details

  • Creators:
  • Corporate Creators:
    University of Texas at Austin. Center for Transportation Research
  • Corporate Contributors:
  • Subject/TRT Terms:
  • Publication/ Report Number:
    FHWA/TX-07/0-5132-1
  • Resource Type:
    Tech Report
  • Geographical Coverage:
  • Edition:
    September 2004–August 2006
  • Corporate Publisher:
    Texas. Department of Transportation
  • Abstract:
    The Texas Department of Transportation (TxDOT) has recently established Hamburg Wheel Tracking Device (HWTD) specification criteria for Superpave mixtures (Item 344). This step has introduced a performance-related feature into an otherwise volumetric mix design approach structured to ensure asphalt mixtures with high shear resistance to rutting. The Superpave mixture design procedure is itself geared toward the production mixtures with high rutting resistance. This, together with the new HWTD criteria, tends to promote “dry” mixtures with lower binder contents than before. While this shift is advantageous for rutting resistance, some reports show that these mixtures are prone to cracking, which is becoming the single largest problem for hot-mix asphalt (HMA) pavements in Texas. In an attempt to produce mixes with higher binder contents to alleviate cracking problems, this research study investigated the possibility of modifying the current design criteria established for Superpave mixtures. The initial findings of this study indicate that the current compaction effort expressed by the number of design gyrations (Ndesign) could be lowered from 100 to 85 without significantly compromising the rutting resistance of the mixes, while improving cracking resistance and durability. An extensive experimental program has been devised to investigate the performance characteristics of asphalt mixtures designed using the revised Ndesign levels and to account for the nominal maximum aggregate size and the concentration of coarse aggregate in the mix. The experimental matrix included two aggregate types (limestone and gravel), three binder grades (PG 64, 70, and 76), and three nominal maximum aggregate sizes (9.5, 12.5, and 19 mm). Although the testing was extensive, the recommendations in this report should be considered preliminary until more experimental evidence is gathered. In addition, by reducing the compaction effort (for the same target density) the voids in the mineral aggregate (VMA) increase, thus making it easy to meet VMA specifications and ensuring a performing mixture.
  • Format:
    PDF
  • Funding:
    0-5132
  • Collection(s):
  • Main Document Checksum:
    urn:sha-512:f2248ba1faca4a0fd85a3c844fe1dcf7959f33e86a214b1c172c0e2f3817e106ccbb9088b7991a116cc3fd73aaf1443db551e667d5cf7575d2392c69843e3127
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  • File Type:
    Filetype[PDF - 2.53 MB ]
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