Minnesota Department of Transportation

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Road Research

NRRA Preventive Maintenance Team

Bio-Materials Maintenance Treatments

Status: Active
Project End Date: November 30, 2021


As asphalt pavement oxidizes and ages, bio-materials can be used to restore flexibility to the asphalt pavement. Recent research at the University has developed bio-rejuvenators that do not have the negative impacts on elastic recovery as measured by the multiple-stress creep recovery test. The research team hypothesizes that these bio-materials can be formulated with asphalt emulsions to seal and soften weathered pavement. The bio-materials are derived from high oleic soybean oil (HOSO) and in the current global trade climate, there exists a need to develop new domestic markets for United States agriculture products, especially soy-products. This study investigates further development of using HOSO-derived technologies for pavement applications and this study is presented with 1:1 matching funds from internal Iowa State University funding sources and the United Soybean Board. Through this project, the research team will investigate formulations for a bio-based asphalt rejuvenating fog seal. The objective of this project is to investigate if a soy-based bio-rejuvenating asphalt emulsion can be formulated to achieve stiffness reduction in oxidized, aged asphalt surfaces. The penetration of bio-rejuvenating sealers into the aged-pavement is important for reducing stiffness and restoring flexibility. This research will develop an asphalt emulsion with and without the HOSO bio-rejuvenator. The asphalt emulsion will act as the vehicle for the soybean-based rejuvenator. Particle size of the emulsion is an important factor for penetration of the bio-sealant. The material developed in this research will be tested at MnROAD on the shoulder of the pavement. Cores will be taken to study the effect of bio-rejuvenating seal on the asphalt. Minnesota DOT will perform friction testing on the control and test sections to determine impacted to pavement friction due to the application of the bio-sealant. The four main steps in this project are bio-sealant emulsion formulation, bio-sealant emulsion field application (pavement shoulders), investigation of stiffness reduction in the field, and studying the effect of the sealant on pavement friction.


The objectives of this research are to:

  1. Enhance pavement longevity by using bio-based materials to soften oxidized asphalt at the surface of the pavement and sealing up cracks in the surface to prevent water infiltration.
  2. Enhance development of soybean-derived bio-materials for pavement maintenance applications.
  3. Broaden the domestic market use for agriculture products in the United States.
  4. Enhance sustainability of pavement materials through the use of bio-materials and reduce pavement life cycle cost through preservation treatments.

The benefits of this research are improved flexibility and preservation of roadways while developing new domestic markets for soybean products. Increased longevity of the roadway delays major rehabilitation and provides improved pavement condition in the interim. Preservation of pavements helps keep roads in better condition longer which leads to reduced pavement life cycle cost.

Project tasks

Task 1: Literature review and recommendations

The research team will compile and summarize current research using bio-based pavement materials with a focus on pavement preservation and current test methods for analyzing bio-rejuvenating asphalt emulsions.

  • Date due: December 30, 2020
  • Deliverable: Literature Review and Presentation to TAP

Task 2: Formulation for bio-rejuvenating maintenance seals and laboratory testing

The research team will investigate formulations for developing the bio-rejuvenating seal. A “control” emulsion slow-set, low viscosity formulation will be developed and tested. The team will build on past bio-modified asphalt formulations for further development into bio-modified asphalt emulsion formulations. The suite of testing includes rotational viscosity testing on the base asphalt(s) to determine the optimum milling temperature for the emulsion. Emulsion testing includes particle size analysis, zeta-potential analysis, stability analysis, percent residue analysis, boil tests to analyze moisture sensitivity of the emulsion, and rotational viscosity testing to analyze emulsion’s sensitivity to shear forces. The asphalt emulsion residue will be tested in the dynamic shear rheometer for final high temperature PG grade. As part of this task, the research team will begin building and ordering parts for the fog seal application unit to use for the placement of fog seal field-trial sections.

  • Date due: March 31, 2021
  • Deliverable: Presentation of laboratory data and benchmark formulation for field testing

Task 3: Field trials

This task will occur in two parts. In Part 1, the research team will work with MnDOT to apply fog seal to a small section of the pavement. The research team will work with MnDOT to apply fog seal to a small section of the pavement. MnDOT will perform dynamic friction testing before and one week after the fog seal application and on a control section. MnDOT will use the dynamic friction tests to determine if a larger field application should be applied. After Part 1 has been approved by MnDOT, the research team will place a field trial section. The purpose of the field trial is to collect lock wheel skid numbers. MnDOT will perform the lock-wheel skid testing. As part of this research contract, the research team will design and/or purchase an emulsion application system and use this to place control fog-seal sections and bio-modified rejuvenating asphalt emulsion with MnDOT approval. Building the unit will begin in Task 2 so the research team can have the equipment ready for when field trials need to be placed. The fog seal application unit will operate as either a gravity-fed system or low-pressure metering using a peristaltic pump. An example of a commercially available low-pressure sealing machine is available at: www.asphaltsealcoatingdirect.com. MnDOT will provide the vehicle such as a gator or a lawnmower to use in the fog-seal application. The research team and MnDOT will work together in an area of parking lot to calibrate the equipment. Field applications will occur under direct supervision of MnDOT and if the placement does not meet expectations, the research team will be notified to stop immediately. If lock-wheel skid numbers are lower than MnDOT requires, MnDOT will correct the roadway shoulders to meet MnDOT requirements at no cost to the research team.

  • Date due: August 31, 2021
  • Deliverable: Presentation about the field trials, materials placed, and initial thoughts

Task 4: Field reports, follow up laboratory testing, and data analysis

The research team will be present at the time of the bio-material application and collect asphalt emulsion in the field for laboratory testing. The laboratory testing will follow the testing plan outlined in Task 2. The field testing will include lock-wheel skid trailer testing performed by MnDOT. The research team will conduct the data analysis to compare no-treatment, “control emulsion”, and “bio-modified emulsion” sections. MnDOT/NRRA will collect three field cores for each section for the research team to perform stiffness analysis in the bending beam rheometer.

  • Date due: October 31, 2021
  • Deliverable: A presentation discussing the test results from field-collected materials and friction testing

Task 5: Draft final report

A draft report will be prepared, following MnDOT publication guidelines, to document project activities, findings and recommendations. This report will need to be reviewed by the technical advisory panel. The research team will hold a TAP meeting to discuss the draft report and any recommended changes. Panel members may be consulted for clarification or discussion of comments.

  • Date due: October 31, 2021
  • Deliverable: Draft final report

Task 6: Final report

The draft report will be updated by the Principal Investigator to incorporate TAP comments or suggestions. The final version of the report will be approved by the panel before this task is considered complete.

  • Date due: November 30, 2021
  • Deliverable: Final report

Project team

Principal Investigator(s): R. Christopher Williams, Gerald and Audrey Professor of Civil Engineering, Civil, Construction, and Environmental Engineering, Iowa State University, rwilliam@iastate.edu
Co-investigator: Eric W. Cochran, Professor, Chemical & Biological Engineering, Iowa State University, ecochran@iastate.edu
Technical Liaison: Jerry Geib, MnDOT, jerry.geib@state.mn.us
Project Technical Advisory Panel (TAP) - email the TAP
Contact us to join this TAP

  • Jerry Geib, MnDOT (TL)
  • Mike Hedlund, MnDOT
  • Brent Holland, MnDOT
  • Todd Kinney, Iowa (Clinton County) / National Counties Engineers
  • Greg Laine, MnDOT
  • Clark Moe, MnDOT
  • Phillip Ruffus, MoDOT
  • Stephanie Weigel, NDDOT

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