Impact of high recycled mixes on HMA overlay crack development rate

Imad L. Al-Qadi, Shenghua Wu, David L. Lippert, Hasan Ozer, Maxwell K. Barry, Fazal R. Safl

Research output: Chapter in Book/Report/Conference proceedingConference contribution

3 Scopus citations


Illinois has many years of experience using various reclaimed materials in highway construction, and in recent years, recycled asphalt shingles (RAS) have been adopted for use in hot-mix asphalt (HMA), along with much higher amounts of reclaimed asphalt pavement (RAP). These reclaimed asphalt materials usually contain aged asphalt binders, which may increase the mix brittleness and hence, pose a challenge for maintaining a flexible pavement and ensuring good performance. To counter these hard asphalt binders, softer asphalts are incorporated into the HMA. The goal Is for the final mix to provide acceptable mix properties for the life of the pavement. To determine the impact of recycled materials on pavement performance, this study monitored nine field projects in terms of the testing, construction, and performance cf surface mixes that have a variety of asphalt binder replacement (ABR) levels from RAP and RAS which used different virgin asphalt binder grades. Simple performance tests (Hamburg wheel tracking test and the Illinois flexibility index test (I-FIT)) were used to evaluate the mix designs. Flexibility index (FI) from the I-FIT showed good correlation with field crack development, especially after first year performance of the mix. Early-Age field performance showed that placing the HMA overlay directly over existing bare concrete pavement or milling off all the HMA and placing the new overlay on concrete pavement results in higher extents of cracking in early age than the sections that left an HMA layer in place. Regardless cf which mix type is designed and what material sources are used, the performance of the mix should be evaluated to ensure it has sufficient flexibility to resist cracking before the mix is used in road construction. This allows owners and contractors to use low-cost reclaimed and recycled materials to the extent possible without negatively impacting pavement performance.

Original languageEnglish (US)
Title of host publicationAsphalt Paving Technology 2017 - Journal of the Association of Asphalt Paving Technologists, AAPT 2017
EditorsGaylon Baumgardner, Y. Richard Kim, Rebecca S. McDaniel, Geoffrey Rowe, Randy West, Audrey Copeland, Adam Hand, Bill Buttlar, Brian Prowell, Jo Daniel
PublisherAssociation of Asphalt Paving Technologist
Number of pages21
ISBN (Electronic)9781605954936
StatePublished - 2017
Externally publishedYes
Event92nd Asphalt Paving Technology Annual Meeting and Technical Sessions 2017, AAPT 2017 - Newport Beach, United States
Duration: Mar 19 2017Mar 22 2017

Publication series

NameAsphalt Paving Technology: Association of Asphalt Paving Technologists-Proceedings of the Technical Sessions
ISSN (Print)0270-2932


Conference92nd Asphalt Paving Technology Annual Meeting and Technical Sessions 2017, AAPT 2017
Country/TerritoryUnited States
CityNewport Beach


  • Balanced mix design
  • Early performance
  • Hot-mix asphalt overlays
  • Illinois flexibility index
  • Recycled mixes

ASJC Scopus subject areas

  • Civil and Structural Engineering


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