Screening of South Dakota Asphalt Mixes for Moisture Damage using Conventional and Innovative Approaches

Moisture-induced damage (also called stripping) is a major distress in asphalt pavements. The loss of strength and durability in asphalt mixes due to the reduction in bond strength between aggregate and binder in presence of moisture is called moisture-induced damage. South Dakota Department of Transportation (SDDOT) and other Departments of Transportation (DOTs) in Region 8 spend millions of dollars annually to combat stripping problem. Also, with increased use of warm mix asphalt (WMA) and mixes containing reclaimed asphalt pavement (RAP), polymer-modified asphalt binders (PMA), and anti-stripping agent (ASA), evaluation of stripping potential of asphalt mixes has become particularly important. For example, there are state- and national-level concerns over the moisture-induced damage potential of WMA mixes. This is due to presence of water in mixes as a result of water injection in foamed WMA mixes and incomplete drying of aggregates at lower WMA mixing and compaction temperatures. Also, some aggregates, upon their incorporation in an asphalt pavement containing some binder sources and/or WMA additives, may lead to a higher moisture-induced damage potential. Therefore, there is an immediate need for evaluation of the effects of different additives and asphalt binder and aggregate sources on pavements’ moisture induced damage potential. As a response to this need, the present study is proposed to evaluate the moisture-induced damage potential of asphalt mixes used in Region 8. More specifically, effects of RAP, WMA, ASA, PMA, and sources of binders and aggregates on moisture-induced damage potential of mixes commonly used by asphalt contractors in South Dakota will be evaluated. Additionally, in an effort to highlight the problematic mixes, aggregates and asphalt binders from recent projects that have shown stripping in the field will also be identified and tested in collaboration with SDDOT. The moisture-induced damage potential of an asphalt mix is generally evaluated using the indirect tensile strength ratio (TSR), which is the ratio between conditioned and unconditioned indirect tensile strengths (ITS) or from the stripping inflection point (SIP) in the Hamburg wheel tracking (HWT) test, in accordance with the American Association of State Highway and Transportation Officials (AASHTO) T 283 and AASHTO T 324 test methods, respectively. Although these tests are widely used by DOTs for screening asphalt mixes, they do not address the failure mechanisms governing the stripping of asphalt pavements, which may cause some misjudgments in prediction of the moisture-induced damage potential. Also, the currently-used approaches for analyzing TSR results are empirical in nature, which do not reflect the field performance of a mix. A number of laboratory studies 2 show that some mixes with relatively low TSR values performed well when tested using the HWT, and vice versa [6,7]. This type of observations raises questions about the reliability of TSR and HWT tests for screening moisture-induced damage potential at the mix design stage. From a mechanistic viewpoint, it is imperative to evaluate the bond strength between asphalt binder and aggregate, to assess stripping. A good adhesion bonding is essential to ensure good resistance to moisture-induced damage and fatigue. In absence of a reliable and quick method for screening of mixes for moisture damage, introducing a simple and quick test and analysis method with a strong mechanistic basis becomes very critical. Therefore, proposing a simple and reliable test method based on the fracture mechanics for screening the moisture-induced damage potential of asphalt mixes was defined as another objective of the present study. The results of this study will be compiled in a database and are expected to help the DOT and asphalt industry in selection of asphalt binders and aggregates to maximize the durability of the asphalt pavements. Therefore, in addition to immediate implementation, the proposed study involves a high degree of novelty.

Language

  • English

Project

  • Status: Active
  • Funding: $194089
  • Contract Numbers:

    DTRT-13-G-UTC38

  • Sponsor Organizations:

    Research and Innovative Technology Administration

    Department of Transportation
    1200 New Jersey Avneue, SE
    Washington, DC  United States  20590
  • Project Managers:

    Kline, Robin

  • Performing Organizations:

    South Dakota State University, Brookings

    Box 2201, AD 130
    Brookings, SD  United States  57007
  • Principal Investigators:

    Ghabchi, Rouzbeh

  • Start Date: 20170328
  • Expected Completion Date: 20180731
  • Actual Completion Date: 0
  • Source Data: MPC-530

Subject/Index Terms

Filing Info

  • Accession Number: 01632410
  • Record Type: Research project
  • Source Agency: Mountain-Plains Consortium
  • Contract Numbers: DTRT-13-G-UTC38
  • Files: UTC, RiP
  • Created Date: Mar 28 2017 3:04PM