Minnesota Department of Transportation

511 Travel Info

Road Research

NRRA Flexible Team

Orange barrels on a highway

MnROAD | NRRA | Structure & Teams | Flexible Team

Field Validation of Using Warm Mix Asphalt at Reduced Production Temperatures for Balanced Mix Design

Status: In development

Project objectives

The asphalt pavement industry has a successful history of using warm mix asphalt (WMA) as compaction aids, but this situation is expected to change as the industry progresses toward the “The Road Forward” initiative to achieve net zero carbon emission by 2050. One of the tactics directed by this initiative is to increase the use of WMA technology to reduce temperatures and emissions from asphalt mixture production. Using WMA at reduced production temperatures can provide not only environmental and economic benefits but also engineering benefits. A NAPA-NCAT case study (link) demonstrates the feasibility of using lower-temperature WMA to improve the cracking resistance of asphalt mixtures for balanced mix design (BMD). Despite the promising results obtained, the case study is limited to a laboratory setting without validation through plant production. Therefore, this research project is proposed to conduct field validation of using WMA at reduced production temperatures for BMD.

The proposed project aims to validate the feasibility of using WMA at reduced production temperatures for BMD through plant production using two field projects. Each project will be comprehensively evaluated through mix design modification, plant production, emission assessment, laboratory performance testing, and pavement performance predictions to determine the environmental and performance impacts of using lower-temperature WMA for asphalt mixture production.

Project tasks

Task 1: Mix design modification for BMD

Two field projects in Missouri and Virginia will be selected for this validation effort. These two states are selected because they have implemented BMD and they allow the use of WMA. Furthermore, the research team has identified a potential asphalt contractor in each state who are willing to support this research. Each project will include a volumetric control mix and two BMD mixes. The volumetric control mix will be obtained from the asphalt contractor, which will then be modified to meet the agency’s BMD performance test requirements using two approaches: 1) add asphalt binder (BMD-1), and 2) use WMA to lower the mixture production temperature (BMD-2).

  • Deliverable: A progress report documenting the mix design optimization efforts and the two resultant BMD mixes

Task 2: Plant production and emission assessment

The three mixes from Task 1 will be produced through an asphalt plant for each field project. The volumetric control mix and the BMD-1 mix will be produced at a typical HMA production temperature, while the BMD-2 mix will be produced at a reduced temperature (by approximately 30 to 50°F) as WMA. A minimum of one-hour production is targeted for each mix to allow the sampling of representative materials for performance testing in Task 3. During production, the fuel usage, particulate matter emission, and visible emission will be monitored. The fuel usage data will also be used to predict CO2 emissions from the production of the control versus BMD mixes.

  • Deliverable: A progress report documenting the production and emission assessment results of the two field projects.

Task 3: Laboratory performance testing

This task aims to determine the impacts of the two BMD modification approaches evaluated in Task 1 on the rutting and cracking resistance of asphalt mixtures and the rheological properties of the extracted asphalt binders. To that end, a comprehensive laboratory testing plan will be conducted on the plant produced mixes sampled in Task 2, which includes the index-based BMD performance tests used by the Missouri and Virginia DOTs (i.e., HWTT, APA, IDEAL-CT, and Cantabro) and two sophisticated cracking tests (i.e., AMPT cyclic fatigue test and modified overlay test). The sophisticated cracking tests can assess the mixture’s cracking resistance under cyclic loading conditions, allowing the results to be used as inputs for pavement performance predictions in Task 4. To consider the impact of aging, all the cracking tests will be conducted after long-term aging, while the rutting tests will be conducted at the short-term aging condition. The laboratory testing plan also includes the Superpave PG, Delta Tc, Frequency Sweep, and Linear Amplitude Sweep tests for characterize the rheological properties of the extracted asphalt binders at various aging conditions.

  • Deliverable: A progress report documenting the laboratory test results..

Task 4: Theoretical pavement performance predictions

This task seeks to determine the impacts of the two BMD modification approaches evaluated in Task 1 on the predicted cracking performance of asphalt pavements and overlays. Theoretical FlexPAVE and TxACOL simulations will be conducted to assess the fatigue cracking of new construction projects and the reflective cracking of overlay projects, respectively, under various underlying pavement, traffic, and climate conditions. The simulation results will provide insights into how BMD modifications through adding asphalt binder and using lower-temperature WMA affect the service life of asphalt pavements and overlays.

  • Deliverable: A progress report documenting the theoretical performance prediction results.

Task 5: Final report and NRRA webinar

Upon completion of Tasks 1 to 4, a final report will be submitted to document the results, findings, and recommendations of the project. Furthermore, an NRRA Research Pays Off webinar will be conducted to disseminate the research findings among SHAs and the asphalt community.

  • Deliverables: A final report and an NRRA Research Pays Off webinar.

Project team

Email the Project Team
Principal Investigators: Fan Yin, f-yin@auburn.edu and Nathan Moore, ndm0005@auburn.edu, National Center for Asphalt Technology at Auburn University
Industry Partners: Jenna Bowers, jennifer.bowers@ingevity.com and Trey Wurst, james.wurst@ingevity.com, Ingevity
Technical Liaison: Emil Bautista, MnDOT, emil.bautista@state.mn.us
Project Technical Advisory Panel (TAP): Contact us to join this TAP

  • Emil Bautista, MnDOT (TL)
  • Elie Hajj, University of Nevada - Reno
  • Dan Kopacz, Wisconsin DOT
  • Raquel Moreas, NCAT
  • Nabil Suleiman, UND
  • Hassan Tabatabaee, Cargill
  • Fujie Zhou, Texas A&M Transportation Institute

Related materials