U.S. Department of Transportation
Federal Highway Administration
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Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
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| This report is an archived publication and may contain dated technical, contact, and link information |
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Publication Number: FHWA-HRT-11-021 Date: April 2011 |
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Recycling asphalt pavement creates a cycle of reusing materials that optimizes the use of natural resources. Reclaimed asphalt pavement (RAP) is a useful alternative to virgin materials because it reduces the need to use virgin aggregate, which is a scarce commodity in some areas of the United States. It also reduces the amount of costly new asphalt binder required in the production of asphalt paving mixtures. This report informs practitioners about the state of the practice for RAP use in the United States as well as best practices for increasing the use of RAP in asphalt pavement mixtures while maintaining high-quality pavement infrastructures. High percentage RAP mixtures are achieved with processing and production practices, resulting in cost and energy savings. Based on an evaluation of pavements containing 30 percent RAP through the Long-Term Pavement Performance (LTPP) program, it has been determined that the performance of pavements containing up to 30 percent RAP is similar to that of pavements constructed from virgin materials with no RAP. This report is of interest to engineers, contractors, and others involved in the specification and design of asphalt mixtures for flexible pavements, as well as those involved in promoting the optimal use of RAP.
Peter Stephanos |
Jorge E. Pagán-Ortiz |
Director, Office of Pavement Technology |
Director, Office of Infrastructure Research and Development |
Notice
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Technical Report Documentation Page
| 1. Report No. FHWA-HRT-11-021 |
2. Government Accession No. | 3. Recipient’s Catalog No. | |
4. Title and Subtitle Reclaimed Asphalt Pavement in Asphalt Mixtures: State of the Practice |
5. Report Date April 2011 |
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6. Performing Organization Code C-00053 |
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7. Author(s) Audrey Copeland |
8. Performing Organization Report No. |
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9. Performing Organization Name and Address Office of Infrastructure Research and Development |
10. Work Unit No. (TRAIS) | ||
11. Contract or Grant No. |
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12. Sponsoring Agency Name and Address Turner-Fairbank Highway Research Center |
13. Type of Report and Period |
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14. Sponsoring Agency Code |
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15. Supplementary Notes The Contracting Officer's Technical Representative (COTR) was Audrey Copeland, HRDI-10. |
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16. Abstract With increased demand and limited aggregate and binder supply, hot mix asphalt (HMA) producers discovered that reclaimed asphalt pavement (RAP) is a valuable component in HMA. As a result, there has been renewed interest in increasing the amount of RAP used in HMA. While a number of factors drive the use of RAP in asphalt pavements, the two primary factors are economic savings and environmental benefits. RAP is a useful alternative to virgin materials because it reduces the use of virgin aggregate and the amount of virgin asphalt binder required in the production of HMA. Using RAP greatly reduces the amount of construction debris going into landfills, and it does not deplete nonrenewable natural resources such as virgin aggregate and asphalt binder. Ultimately, recycling asphalt creates a cycle of reuse that optimizes the use of natural resources and sustains the asphalt pavement industry.
More widespread use of higher amounts of RAP in asphalt mixtures requires support from State transportation departments and the HMA industry. State transportation departments have expressed concern over the lack of guidance on the use of high percentages of RAP (high RAP) mixtures, as well as the lack of information on their performance. As a result, there is a need for national guidance on best practices when using RAP and documented information about long-term performance of high RAP pavements.
The intent of this report is to provide state-of-the-practice information on including higher amounts of RAP in asphalt mixtures. The state of the practice for RAP use across the United States, as well as common challenges for increasing the use of RAP, are identified. Best practices applicable for the use of RAP are presented to identify general parameters that must be considered when developing specifications and to provide information on available resources and best practices for sourcing, processing, stockpiling, testing, designing, evaluating, producing, and placing high RAP mixtures, as well as practices to attain the best performance for high RAP mixtures. |
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17. Key Words Reclaimed asphalt pavement (RAP), Recycled asphalt, Hot mix asphalt (HMA), Asphalt mixtures, Superpave®, Performance |
18. Distribution Statement No restrictions. This document is available to the public through the National Technical Information Service, Alexandria, VA 22312. |
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19. Security Classif. (of this report) Unclassified |
20. Security Classif. (of this page) Unclassified |
21. No. of Pages 55 |
22. Price |
Form DOT F 1700.7 (8-72) Reproduction of completed pages authorized
SI* (Modern Metric) Conversion Factors
CHAPTER 2. STATE OF THE PRACTICE FOR RAP USE
CHAPTER 3. BEST PRACTICES FOR INCREASING RAP USE
CHAPTER 4. CONCLUSIONS AND RECOMMENDATIONS
Abbreviations
| AASHTO | American Association of State Highway and Transportation Officials |
| AC | Asphalt content |
| AMPT | Asphalt mixture performance tester |
| BSG | Bulk specific gravity |
| Caltrans | California Department of Transportation |
| CDOT | Colorado Department of Transportation |
| DOT | Department of Transportation |
| DSR | Dynamic shear rheometer |
| ESAL | Equivalent single axle load |
| ETG | Expert task group |
| FHWA | Federal Highway Administration |
| HMA | Hot mix asphalt |
| IRI | International roughness index |
| JMF | Job mix formula |
| LTPP | Long-Term Pavement Performance |
| MTO | Ministry of Transportation of Ontario |
| NAPA | National Asphalt Pavement Association |
| NCAT | National Center for Asphalt Technology |
| NCDOT | North Carolina Department of Transportation |
| NCHRP | National Cooperative Highway Research Program |
| ODOT | Ohio Department of Transportation |
| PG | Performance grade |
| QC | Quality control |
| RAP | Reclaimed asphalt pavement |
| RTFO | Rolling thin film oven |
| SCDOT | South Carolina Department of Transportation |
| VMA | Voids in the mineral aggregate |
| WMA | Warm mix asphalt |
Symbols
| A | RAP percent binder content |
| B | RAP percent in mixture |
| C | Total percent binder content in mixture |
| |E*| | Mix dynamic modulus |
| G* | Shear modulus |
| Gb | Asphalt specific gravity |
 | Bulk specific gravity of RAP aggregate |
 | Effective specific gravity of RAP aggregate |
 | Maximum theoretical specific gravity of the RAP mixture |
| Pb | Asphalt content of the RAP mixture |
| Pba | Asphalt absorption |
| TBlend | Critical temperature of blended asphalt binder |
| Tc(High) | Critical high temperature |
| Tc(Int) | Intermediate critical temperature |
| Tc(Low) | Low critical temperature which is the higher of Tc(S) or Tc(m) |
| Tc(m) | Critical low temperature based on m-value |
| Tc(S) | Critical low temperature based on s-value |
| TRAP | Critical temperature of recovered RAP binder |
| Tvirgin | Critical temperature of virgin asphalt binder |
