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South Dakota Department of Transportation
Project Synopsis
SD2011-08


Title: Improved Performance of Reclaimed Asphalt Pavement Mixes
Project Researcher: ,
Project Manager:
Research Period: 9/26/2012 - 3/31/2014
Status:
Cost: $60,000.00

Problem Statement:As paving material costs escalate, reclaimed asphalt pavement (RAP) is becoming more valuable, primarily to supplement asphalt concrete mixes where its full benefits can be realized. The South Dakota Department of Transportation (SDDOT) routinely uses reclaimed asphalt materials, but with mixed results. Even at the typical content of 20% reclaimed materials, serious increases in raveling and cracking have been observed at times. A few recently constructed pavements are expected to last only a fraction of their normal life. While SDDOT has allowed as high as 50% reclaimed materials in some cases, the risk of reduced performance appears to be significant. The department currently applies conventional pavement preservation practices to RAP pavements and is uncertain if there are benefits to be gained from modifying this approach. Despite similarities between producing virgin and RAP asphalt mixtures, there are still challenges to maximizing RAP content and attaining performance comparable to conventional asphalt mixes. Common barriers to state transportation departments’ and contractors’ use of more RAP include: ? availability of suitable RAP materials; ? imposed limitations on RAP percentage; ? difficulty in determining the appropriate amount and grade of virgin asphalt binder in blended mixes; ? difficulty in achieving uniform coating of aggregate in blended mixes; ? quality and consistency of RAP blended mixes, especially with high RAP content and polymer- modified binders; ? introduction of excessive fines and moisture from RAP into the mix; ? stiffening of the mix and resulting diminished resistance to fatigue cracking; ? uncertainties associated with adding other reclaimed materials, such as asphalt shingles; ? inferior or inconsistent performance of reclaimed mixes. Research is needed to better understand proper methods for incorporation of RAP into AC mixes to achieve acceptable performance and to identify strategies that will allow SDDOT to use RAP to its fullest potential in a variety of paving applications.

Findings:

Research Objectives:
1  Describe current practices for specification, design, production, testing, pavement preservation, and placement of RAP in various types of hot mix and warm mix paving operations in South Dakota and nationally.
2  Identify best practices for specification, design, production, testing, and placement of RAP.
3  Suggest revisions and refinements to SDDOT specifications, practices, and pavement preservation practices, and develop guidance for using recycled asphalt materials in pavements.

Research Tasks:
1  Meet with the project’s technical panel to review the project work plan.
2  Review existing literature to determine current practices for specification, design, production, testing, pavement preservation, and placement of RAP nationwide and regionally.
3  Through review of SDDOT specifications and interviews with select SDDOT staff and contractors with experience in the use of RAP, describe and assess the state-of-practice and identify concerns regarding use of RAP in South Dakota.
4  Develop a list of interview candidates and an interview guide designed to elicit information from other state departments of transportation in the region with demonstrated expertise in successful application of RAP mixes (including high-content RAP hot and warm mixes) on specifications and practices for design, production, testing, placement, pavement preservation, and long-term performance of RAP.
5  Submit and present a technical memorandum summarizing the results of the literature review, the review of South Dakota specifications, practices, and concerns, and the proposed interviews of other state transportation departments.
6  Upon approval of the technical panel, conduct and summarize findings of the interviews of other state transportation departments.
7  Based on information gleaned from the previous tasks, prepare and present a technical memorandum that identifies best practices, suggests revisions and refinements to SDDOT specifications and practices, and outlines guidance for pavement preservation and for using recycled asphalt materials in pavements.
8  Meet with the project technical panel to present project findings and to review the outline of guidance.
9  In conformance with Guidelines for Performing Research for the South Dakota Department of Transportation
10  Prepare a final report and executive summary of the research methodology, findings, conclusions, and recommendations.
11  Make an executive presentation to the SDDOT Research Review Board at the conclusion of the project.

Documents Available:
SD2011-08 Final Report.pdf
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