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Reflective Cracking of Flexible Pavements Phase I and II Final Recommendations
  • Published Date:
    2008-02-02
  • Language:
    English
Filetype[PDF-643.12 KB]


Details:
  • Publication/ Report Number:
    080-07-803
  • Resource Type:
  • Geographical Coverage:
  • NTL Classification:
    NTL-HIGHWAY/ROAD TRANSPORTATION-Design ; NTL-HIGHWAY/ROAD TRANSPORTATION-HIGHWAY/ROAD TRANSPORTATION ; NTL-HIGHWAY/ROAD TRANSPORTATION-Pavement Management and Performance ;
  • Format:
  • Abstract:
    This report summarizes all the findings and recommendations from the Phase I and Phase II of the Nevada Department of Transportation (NDOT) study initiated in 2006 to mitigate reflective cracking in hot mix asphalt (HMA) overlays. Based on the analysis of the various findings it was recommended to further evaluate the stress relief course (SRC) as a reflective cracking mitigation technique under Nevada’s conditions. It should be noted that the SRC used by NDOT was not specifically designed or checked for its reflective cracking resistance and only consisted of a 1-inch of the typical Type II (1” max size) dense graded HMA mix placed between the existing HMA and the overlay. This NDOT study revealed promising performance for the SRC when specifically designed to resist reflective cracking. Additionally, for a good overall performance, the SRC needs to be coupled with an overlay mix with a good resistance to reflective cracking. Current state highway agencies’ specifications for SRCs were reviewed and are summarized in this report. The review revealed specifications for SRCs in six different states. Four of those states: Arizona, California, Florida, and Massachusetts, specify an asphalt-rubber stress absorbing membrane interlayer (SAMI) which consists of an application of asphalt rubber binder followed by an application of aggregate. Texas DOT specifies a Crack Attenuating Mixture (CAM) which consists of an HMA mix designed according to the Superpave design procedure to a target air void of 2% at 50 gyrations along with criteria for the Hamburg Wheel and the Texas Transportation Institute (TTI) Overlay tests. The Utah DOT specifies a reflective cracking relief bituminous mixture which meets the general requirements specified for an HMA mixture except the mix is designed to a target air void of 0.5-2.5% at 50 design gyrations along with criteria for voids in mineral aggregate (VMA), Hveem stability, and flexural beam fatigue testing at optimum binder content. Based on the limited success of SRCs in Nevada and the review of the states’ specifications for SRCs, it is recommended to conduct an extensive laboratory evaluation for the Texas DOT and the Utah DOT SRC designs using Nevada’s materials during 2008. The results of the laboratory evaluation will be used to make recommendations for field evaluation during 2009. The overlay thickness will be designed using the Rubber Pavements Association Overlay Design Model. Field mixtures from the SRC and overlay mixes will be collected during construction from behind the paver and evaluated in terms of their dynamic modulus, fatigue resistance, rutting resistance using the repeated load triaxial (RLT) test, thermal cracking resistance using the thermal stress restrained specimen test (TSRST), reflective cracking resistance using the TTI Upgraded Overlay tester, and moisture sensitivity. The performance of the field test sections will be monitored and field cores will be sampled for evaluation in the TTI Overlay Tester. Based on the laboratory evaluation and the field performance, the specifications for reflective cracking resistance will be adjusted and the most effective technique will be selected.

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