Effectiveness of Softening Agents for Enhancing Properties of Asphalt Mixes with High RAP Contents

The use of reclaimed asphalt pavement (RAP) in hot mix asphalt (HMA) has increased in recent years due to the increasing costs and demands for crude oils and aggregates. However, the use of high RAP (over 25% by the weight of total mix) in new mixes may have some performance issues such as low resistance due to fatigue cracking. This is mainly due to the excessive oxidative aging RAP being used in the mix, and it becomes more problematic when high RAP is used. To mitigate this problem, mixes with RAP usually require the use of a softer binder (e.g., PG 58-22) or a softening agent. However, the use of a softer binder puts the contractor in a non-compliance situation as it is not often an approved Performance Grade (PG) binder (e.g., PG 58-28). For instance, the Arkansas Department of Transportation (ArDOT) allows only PG 64-22, PG 70-22, and PG 76-22 on its highways. Furthermore, a PG 58-28 binder is more expensive than the base binder (PG 64-22). The second solution of using a softening agent appears to be a good alternative to enhance the performance of high RAP mixes as it will allow contractors to use ArDOT approved binders without increasing the cost of materials significantly. The aim of the proposed study is to determine the effectiveness of different rejuvenators on blended binders’ rheological and mechanistic properties by means of traditional test methods (e.g., Superpave) and non-traditional techniques such as the atomic force microscopy (AFM). The test results will reveal macro, micro- and nano-level mechanistic performance data of the blended binders. Binders from two RAP samples will be recovered, and they will be blended with two base binders. As the softening agents, a commercial rejuvenator (Evotflex® CA) and two waste products, namely waste cooking oil (WCO) and engine bottom oil (EBO) will be investigated in this study. Different amounts of RAP binders and rejuvenators will be tried to know their optimum dosages. Also, two plant mix samples with high RAP will be collected and tested for volumetric and performance analysis. The performance data of the constructed field sections will be collected and analyzed. This study will be pursued in cooperation with a local asphalt producer (Atlas Paving Co.), a refinery (Ergon), and ArDOT. The collaborative efforts with industry partners are expected to enhance through this project. The use of high RAP is expected to be huge cost savings for transportation. Further, the sustainable use of WCO and EBO will facilitate the use of commercial waste products. Thus, the proposed study supports the Center’s vision, “in partnership with major state authorities and other public and private organizations in the region, will allow it to become a transportation focal point in the region.” Experimental data gathered from this study are expected to give confidence to state and local transportation agencies, and contractors in the region. The design and quality-control guidelines developed from the proposed study are expected to be implemented by state and industry partners. The proposed study will facilitate in meeting the following objectives of Tran-SET: (1) Promote sustainability and resiliency of the transportation infrastructure renewal and upgrade; (2) Introduce and implement cost-effective solutions to the transportation infrastructure backlog of projects; (3) Develop cost-effective solutions for the construction and maintenance of the transportation infrastructure in metropolitan and rural areas; (4) Promote workforce development through learning and continuous education. The proposed study is aligned with a regional priority “Multiscale characterization of recyclable waste materials in transportation applications for achieving the economic and financial sustainability,” with a primary focus of “Recycling infrastructure assets.” Locally generated waste materials, which are environmental burdens to the society, will be utilized in preparing new mixes. Besides regional priorities, this project strongly supports the Center’s focus areas 4 and 5. This study will develop tools and materials for longer-lasting infrastructure, assess the feasibility of using local industrial wastes, and enhance collaborative records with industry partners. The major benefits of the proposed study are to: (a) reuse of waste materials, (b) enhance training opportunities for students in the region and build a future workforce.


  • English


  • Status: Completed
  • Funding: $ 60500
  • Contract Numbers:


  • Sponsor Organizations:

    Office of the Assistant Secretary for Research and Technology

    University Transportation Centers Program
    Department of Transportation
    Washington, DC  United States  20590
  • Managing Organizations:

    Transportation Consortium of South-Central States (Tran-SET)

    Louisiana State University
    Baton Rouge, LA  United States  70803
  • Project Managers:

    Mousa, Momen

  • Performing Organizations:

    Arkansas State University

    Department of Engineering
    P.O. Box 1740
    State University, AR  United States  72467
  • Principal Investigators:

    Hossain, Zahid

  • Start Date: 20200801
  • Expected Completion Date: 20220201
  • Actual Completion Date: 0
  • USDOT Program: University Transportation Centers Program

Subject/Index Terms

Filing Info

  • Accession Number: 01757531
  • Record Type: Research project
  • Source Agency: Transportation Consortium of South-Central States (Tran-SET)
  • Contract Numbers: 69A3551747106
  • Files: UTC, RIP
  • Created Date: Nov 10 2020 8:05PM