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South Dakota Department of Transportation
Project Synopsis
SD2008-03


Title: Evaluation of Warm Mix Asphalt Concrete Pavement in South Dakota Conditions
Project Researcher: Peter Sebaaly, University of Nevada, Reno
Project Manager: Christina Bennett
Research Period: 10/15/2008 - 9/30/2012
Status: Approved
Cost: $140,000.00

Problem Statement: Highway construction techniques employing warm mix asphalt (WMA) have been introduced in the U.S. over the past few years as a means to allow pavement compaction at lower temperatures, increase construction efficiency, and provide better environmental stewardship. Warm mix asphalt is produced at temperatures in the range of 30 degrees to 100 degrees F lower than typical hot mix asphalt (HMA). Because WMA is produced at a lower temperature than HMA, a primary benefit to using WMA is a reduction in fuel consumption compared to the amount of energy needed to heat traditional HMA. Lower temperatures during asphalt production allow for reduced emissions at the plant and around the paving site. Decreased fuel use would also have the potential to reduce the construction costs for asphalt paving projects.

WMA lowers the viscosity of asphalt concrete. By lowering the viscosity, benefits might include better compaction, slower cooling rates, reduced mixture aging, allowance for longer haul distances, and more options for maintenance activities like patching in colder weather. These conditions may result in better capabilities to pave and compact at cooler temperatures, such as those experienced in South Dakota during the early and late construction season, and thus provide more options for paving operations during less than ideal weather conditions.

To assess the relative merits of employing WMA paving techniques in the state, the South Dakota Department of Transportation (SDDOT) would need to construct pavement test sections with WMA. The primary aims of WMA evaluation would be to:

- examine the suitability of using WMA in South Dakota's climate;

- assess WMA pavement and paving operations in overlays, interim surfacing, and/or leveling courses;

- evaluate the mechanistic and chemical properties of WMA binders and mixtures;

- assess the performance of quartzite, limestone, and natural gravels in WMA pavements, which are the 3 primary aggregate types native to South Dakota, and also perform similar assessments relative to various quantities by weight of recycled asphalt pavement (RAP);

- ascertain the structural integrity, durability, and moisture susceptibility of WMA in comparison to conventional HMA pavements;

- gain measures of relative emissions during production and paving with WMA as compared to HMA.

To fully accomplish the desired WMA assessment, the test pavement construction should not be a simple thin overlay or wearing course. A simple thin overlay wouldn`t necessarily give a full representation of structural integrity. Also, paving operations should be scheduled late in the construction season when the weather is cooler to truly determine whether WMA placement is a viable alternative during less than ideal weather conditions. Finally, test sections would need to be monitored for an extended period of time after construction.



Findings:

Research Objectives:
1  Evaluate various types of WMA paving technologies to determine their suitability for use in South Dakota in various applications.
2  Assess the performance of WMA through construction of test sections and subsequent monitoring of the sections' performance over time.
3  Obtain cost versus benefit analyses relative to the constructability, performance, environmental factors, and other potential considerations.

Research Tasks:
1  Review and summarize literature that can be directly related to the construction and performance of WMA pavements in South Dakota.
2  Review the publication on the National Asphalt Pavement Association website, "Material Test Framework for Warm Mix Asphalt Trials” as this document will be used after modification based on discussions between the project Technical Panel and Research
3  Develop a preliminary lab protocol and testing plan including appropriate testing procedures for the WMA mix designs to be reviewed and approved by the Technical Panel. This will be based on the South Dakota AC mix design procedure and should include
4  Meet with the project's Technical Panel to review and discuss the project scope, preliminary work plan, and “Material Test Framework for Warm Mix Asphalt Trials.
5  Conduct preliminary testing and provide an interim report, for review and approval by the Technical Panel that includes initial lab test results and also the proposed test section matrix for WMA field trial sections.
6  Meet with technical panel to finalize testing plans and overview the proposed content plan notes.
7  Develop plan notes for the construction of WMA test sections that will incorporate all modifications to standard SDDOT plan notes and specifications for HMA pavements, including specifications for admixtures, special binders, and other additives, as
8  Document construction of the WMA test sections and HMA control sections, document emissions and energy reductions of WMA and HMA, and also conduct field testing and monitoring according to the “Material Test Framework for Warm Mix Asphalt Trials” as
9  Conduct long-term performance monitoring of all WMA test sections and HMA control sections, including the testing of pavement core samples to be provided by the SDDOT over at least two winters.
10  Develop cost versus benefit analyses of WMA relative to the constructability, performance, environmental factors, and other potential considerations as compared to HMA.
11  Develop recommendations for the suitability, as well as the application of evaluation and acceptance procedures relative to new WMA technologies that could be incorporated into paving practices in South Dakota.
12  Prepare a final report and executive summary of the work efforts, findings, conclusions, cost versus benefit analyses, and recommendations.
13  Make an executive presentation to the SDDOT Research Review Board at the conclusion of the work efforts.

Documents Available:

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