Home Skip to main content

Research Projects (2008-09)

Identifying Number


Project Title

Effectiveness of Using Recycled Asphalt Materials and other Dust Suppressants in Gravel Roads, Year 2


University of Wyoming

Project Investigators

George Huntington and Khaled Ksaibati

Description of Project Abstract

With the recent influx of oil and gas drilling in the Rocky Mountains region, local jurisdictions are seeing substantial increases in traffic, particularly trucks, on their road networks. Often this results in increased maintenance costs that are out of reach of many local jurisdiction budgets.

Gravel loss, primarily in the form of dust, is a common problem on Wyoming's gravel roads. This loss both degrades the road surface and creates environmental problems. For both engineering and environmental reasons, it is in the best interests of the roads' owners and users to minimize dust loss and provide a good road surface.

As vehicles kick up dust and it blows away, the gravel surfacing loses the binding effects of fine particles. Then, washboards – rhythmic corrugations – develop on the road surface; when the loss of fine material makes the surface more permeable, more water is trapped on the surface, leading to more potholes.

When dust enters the air, it increases the risk of violating federal air quality standards. Figure 1 shows the national distribution of non-attainment areas for PM-10 particulates. Sheridan County, Wyoming is one of these non-attainment areas. As more traffic travels Wyoming's gravel roads, the risk posed by fugitive dust will only increase unless steps are taken to reduce this air quality problem.

Figure 1
Figure 1. USEPA Nonattainment areas for PM-10 particulate matter, November 2006 (1)

Many unpaved county roads throughout the State carry in excess of 1,000 vehicles per day (vpd), yet typical recommendations for when to pave an unpaved road range from 150 to 400 vpd. For financial reasons, many counties are unable to pave roads, even though they know that in the long run, paving is the most economical solution. Further complicating the issue is the knowledge that on many of these roads, traffic volumes will drop when drilling activities slow. Unfortunately, no one has a crystal ball that tells them just how much drilling activity will take place over the next few decades. Considering these factors, it is important to know the most cost effective ways of managing unpaved roads, even at higher traffic volumes.

A number of study sections on Schoonover and Dead Horse roads in Johnson County, Wyoming will be reconstructed during the 2008 construction season. These roads carry in excess of 1,000 vpd; the predominant traffic type is trucks serving drilling activities. Construction will be administered by Johnson County and monitored by the Wyoming T2/LTAP Center (T2). Gravel samples will be taken by the Wyoming T2/LTAP and then tested by the Wyoming Department of Transportation's Materials Program. Sections will be monitored for two years. Maintenance activities and expenses will be tracked by T2/LTAPwith assistance from Johnson County and any other organizations performing maintenance activities on the studied sections. Traffic and dust loss will be monitored by T2/LTAP. Weather data will be collected or obtained from other sources. Analysis will be performed after two years of monitoring, with the goal of determining the most cost effective approach to constructing and maintaining unpaved roads. In addition, specific recommendations will be made on the effectiveness of using RAP on gravel roads.

Project Objectives

This study seeks to address both structural and surfacing issues associated with unpaved roads subjected to heavier traffic applications. Different gravel types with various dust suppressants including recycled asphalt pavement (RAP) and soil stabilizers will be evaluated in an attempt to provide the best road surface at the least total cost. In general, unpaved roads have lower initial construction costs but higher maintenance costs than paved roads. Balancing construction costs, maintenance costs, vehicle wear and tear, rider comfort, and safety should be the objective of any organization responsible for unpaved roads. This study seeks to provide information that will allow organizations to minimize the total costs on their unpaved roads. In addition, this study will provide counties in Wyoming and across the region with specific information on the cost effectiveness of using RAP in gravel roads. WYDOT is committed to provide one million dollars worth of RAP to counties which makes is it important to make sure that the RAP is used effectively.

Project Approach/Methods

The following tasks will be performed in the second year of this project:

Task 1- Literature Review: The initial literature review revealed no documentation on RAP utilizations on gravel road. A more comprehensive review of the literature will be completed.

Task 2-Site Selection and Experimental Design: In addition to the test sections in Laramie and Johnson counties, more test sections will be selected in Sweetwater County.

Task 3-Construction:
The additional study sections will be constructed and this construction will be monitored and documented.

  • a) Sample collection
    Samples of all materials used and, when possible, of the subgrade and subbase materials will be collected during construction. Sampling should probably be done with a shovel from the windrow.
  • b) Drainage assessment
    The drainage on each study section will be evaluated. Detailed geometric assessments should result in an overall number for the quality of drainage at each site, using the standards developed as part of T2/LTAP's asset management program.
  • c) Construction documentation
    The construction procedures will be documented through photographs, videos, written reports, and cost and quantity documents. Labor, materials, and equipment costs should be carefully documented to get accurate values for construction costs.

Task 4-Laboratory Testing: Laboratory tests will be performed on the materials sampled during construction. If regraveling is performed during the course of this study, the new gravel should also be sampled and tested. Tests will include gradation, plastic and liquid limits, fractured faces, fine aggregate angularity, and standard proctor tests. In addition, strength tests such as R-value or CBR will be performed. Subsequent testing may be performed on field samples taken to evaluate aggregate degradation. The WYDOT's Materials program agreed to perform these tests.

Task 5-Monitoring:

  • a) Traffic monitoring
    Traffic speeds, volumes, and types will be monitored.
  • b) Weather monitoring
    Weather will be monitored on-site or weather data will be obtained form other sources.
  • c) Surface conditions
    The road surface conditions will be evaluated periodically, at least once per month.
  • d) Maintenance
    All maintenance activities will be documented and costs will assigned to each study section.

Task 6-Interim Report: Reports on the results obtained will be delivered in written summaries one year after construction, containing all monitoring results, and referencing the construction report.

Task 7- Final Analysis and Report Preparation: The data collected will be analyzed and reports of the findings will be prepared. The main emphasis will be on ways of minimizing the total costs of constructing, maintaining, and operating vehicles on the study sections.

Task 8-Presentation of results: The results will be presented to the sponsors, to industry, to local governments, and to the academic community.

MPC Critical Issues

Low Volume Roads and Bridges

Contributions/Potential Applications of Research

This project will be very beneficial to all local agencies dealing with gravel roads in the region. Selecting the appropriate combinations of materials and stabilization agents/techniques will insure utilizing the limited resources available to build and maintain high volume gravel roads. In addition, this project will help local agencies in determining the cost effectiveness of utilizing RAP in gravel roads.

Technology Transfer Activities

The Wyoming LTAP center will hold several workshops statewide to insure the proper implementation of this study. In addition, Wyoming Tech Briefs will be distributed to all local agencies. Efforts will be also made to distribute the Tech Briefs to other interested agencies in our region.

Total Project Cost


MPC Funds Requested


TRB Keywords

Gravel roads, design and performance of gravel roads, unpaved roads, dust control, road stabilization, low volume roads, surfacing gravel

List of References

  1. USEPA website, http://www.epa.gov/oar/oaqps/greenbk/mappm10.html, accessed February 9, 2007.
  2. Huntington and Ksaibati, 2007.
  3. Eaton, R.A., S. Gerard, and D.W. Cate, Rating Unsurfaced Roads: A field manual for measuring maintenance problems, USACE-CRREL, Special Report 87-15, revised September 1988.
  4. Walker, D., Gravel – PASER Manual: Pavement Surface Evaluation and Rating, Wisconsin Transportation Information Center, Madison, WI, 1989.
  5. Jonathan Q. Addo, Thomas G. Sanders, and Melanie Chenard: Road Dust Suppression: Effect on Maintenance Stability, Safety and the Environment, Phases 1-3, MPC report, May, 2004.
  6. Sanders, T.G. and J.Q. Addo. "Experimental Road Dust Measurement Device." Journal of Transportation Engineering, ASCE. 2000.
NDSU Dept 2880P.O. Box 6050Fargo, ND 58108-6050