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Improving Durability of Asphalt Mixtures

File Language:
English


Details

  • Creators:
    Shuler, Scott
  • Corporate Creators:
    Colorado State University
  • Corporate Contributors:
  • Subject/TRT Terms:
  • Publication/ Report Number:
    CDOT-2019-06
  • Resource Type:
    Tech Report
  • Geographical Coverage:
  • Edition:
    Final Report
  • Corporate Publisher:
    Colorado. Dept. of Transportation. Applied Research and Innovation Branch
  • Abstract:
    Some of the hot mix asphalt pavements constructed for CDOT prior to 2016 have demonstrated premature cracking and raveling distress. The appearance of these pavements is reported to be that of pavements which contain lower than desirable asphalt binder content. However, quality control and quality assurance data obtained from these projects indicates that asphalt content, VMA and dust to asphalt ratio are all within acceptable mixture design and specification limits. This could mean that current mixture design and specification limits are not appropriate for these pavements or that adjustments to asphalt content may be necessary during construction due to changes in asphalt mixture proportions. The two objectives for this research were to review the 2016 asphalt mixture specifications to determine whether changes were warranted that could lead to more durable asphalt mixtures and, if so, adjust the specification accordingly and construct test sections to evaluate the revised specification. The results of this work lead to the conclusion that the dust to asphalt ratio determined during mixture design, while calculated in accordance with the recommendations of the Strategic Highway Research Program (SHRP) for the Superpave Mixture Design procedure were correct, the 1 percent hydrated lime required for each mixture design was not being counted as dust. This meant that dust to asphalt ratio was actually higher than calculated. In addition, VMA was lower than recommended based on nominal maximum aggregate size. This occurred because of changes to the mixture nominal maximum aggregate size during construction. A test pavement was constructed in 2017 to determine if changes in the dust to asphalt content to account for 1 percent hydrated lime and an increase in VMA would produce improved durability. At this writing, two years after construction, no apparent differences in performance are evident between test and control sections.
  • Format:
    PDF
  • Funding:
    416.02
  • Collection(s):
  • Main Document Checksum:
    urn:sha-512:99111b5994422a777e95d08517a1d49d86a28102961e980be7c435a461ab6664f755418ff381e137387c57e03000e039225874c623c6f3a9cd4be758c69fa9ed
  • Download URL:
  • File Type:
    Filetype[PDF - 6.06 MB ]
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