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REPORT
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Publication Number:  FHWA-HRT-17-111    Date:  September 2018
Publication Number: FHWA-HRT-17-111
Date: September 2018

 

Proposed Performance-Prediction Equations and Threshold Triggers for Thin-Overlay Treatments Using The Long-Term Pavement Performance Database

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FOREWORD

This paper won the Challenge category of the 2015–2016 International Data Analysis Contest, which was sponsored by the Federal Highway Administration’s Long-Term Pavement Performance (LTPP) program and the American Society of Civil Engineers. This paper, entitled Proposed Performance-Prediction Equations and Threshold Triggers for Thin-Overlay Treatments Using the Long-Term Pavement Performance Database, analyzes the use of thin overlays as a pavement-preservation treatment for prolonging the life of a pavement.

The research team proposes a methodology that analyzes survey data on pavement condition to determine the optimal time to apply a thin-overlay treatment to achieve a target pavement-life extension. Different climatic zones, traffic levels, and existing pavement conditions were considered to investigate the effectiveness of thin-overlay treatments.

The main objective of this study was to develop guidelines and/or parameters that highway agencies can use to determine the most appropriate time to apply thin-overlay treatments based on the condition of the existing pavement.

The results demonstrated that threshold triggers based on longitudinal cracking in the wheel path and rutting severity can be used to select the most appropriate time to apply a thin overlay. This report presents empirical equations to predict the life gain that can be achieved by a thin-overlay treatment based on the existing pavement conditions. The predicted life gain due to a thin-overlay treatment was found to be a function of the traffic level and the thickness of the existing asphalt-concrete layer.

Cheryl Allen Richter, Ph.D., P.E.
Director, Office of Infrastructure Research and Development

Notice

This document is disseminated under the sponsorship of the U.S. Department of Transportation (USDOT) in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document.

The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers’ names appear in this report only because they are considered essential to the objective of the document.

Quality Assurance Statement

The Federal Highway Administration (FHWA) provides high-quality information to serve Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement.

 

Technical Report Documentation Page

1. Report No.

FHWA-HRT-17-111

2. Government Accession No.

 

3 Recipient's Catalog No.

 

4. Title and Subtitle

Proposed Performance-Prediction Equations and Threshold Triggers for Thin-Overlay Treatments Using the Long-Term Pavement Performance Database

5. Report Date

September 2018

6. Performing Organization Code

 

7. Author(s)

Michael D. Elwardany, Kangjin Lee, Jung Hwa Lee, Coleman Brown, Cassie Castorena, and Y. Richard Kim

8. Performing Organization Report No.

 

9. Performing Organization Name and Address

North Carolina State University
Department of Civil, Construction, and Environmental Engineering
Campus Box 7908, Raleigh, NC 27695

10. Work Unit No. (TRAIS)

 

11. Contract or Grant No.

 

12. Sponsoring Agency Name and Address

Office of Infrastructure Research and Development
Federal Highway Administration
6300 Georgetown Pike
McLean, VA 22101

13. Type of Report and Period Covered

Final Report; January 6, 2017–June 1, 2017

14. Sponsoring Agency Code

HRDI-30

15. Supplementary Notes

The Contracting Officer’s Representative for this report was Deborah Walker (HRDI-30).

16. Abstract

The purpose of pavement-preservation treatments is to correct surface defects, improve ride quality, improve safety characteristics, and extend pavement life without increasing the structural capacity of the pavement. The application of a thin overlay is expected to extend the life of a pavement by 8–10 yr, although this range may vary depending on traffic, environmental conditions, quality of the materials, and workmanship. Thin overlays do not significantly increase the structural capacity of a pavement. Thus, the existing pavement condition should be evaluated carefully prior to the application of a thin overlay to ensure that structural rehabilitation is not necessary. A set of guidelines to determine the best time to apply thin-overlay treatments would help highway agencies optimize their budgets, thereby leading to potentially significant taxpayer savings.

 

The objective of this study was to develop guidelines, parameters, and performance-prediction equations to select the most appropriate time to apply a thin-overlay treatment based on the condition of the existing pavement. To arrive at the proposed guidelines, data from the Long-Term Pavement Performance (LTPP) Program Specific Pavement Studies 3 and 5 were used to evaluate the effects of climate, traffic, existing asphalt concrete (AC)–layer thickness, and overlay thickness on the life extension that results from the application of thin-overlay treatments.

 

The results demonstrate that threshold triggers based on longitudinal cracking in the wheel path and rutting severity can be used to select the best time to apply a thin overlay in order to achieve a target pavement-life extension. Analysis of the LTPP data shows that both the traffic level and existing AC-layer thickness significantly affect the life extension that results from the application of a thin overlay in terms of retarding rutting and longitudinal cracking, respectively. This paper presents empirical equations to predict the life gain that can be achieved from a thin-overlay treatment based on the existing pavement conditions.

17. Key Words

Thin overlay, performance prediction, rutting, longitudinal cracking, Long-Term Pavement Performance (LTPP) Program

18. Distribution Statement

No restrictions. This document is available to the public through the National Technical Information Service, Springfield, VA 22161.
http://www.ntis.gov

19. Security Classification
(of this report)

Unclassified

20. Security Classification
(of this page)

Unclassified

21. No. of Pages

32

22. Price

 

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized

 

 

 

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