Technical Report Documentation Page 1. Report No. FHWA/TX-09/0-5123-3 2. Government Accession No. 3. Recipient's Catalog No. 4. Title and Subtitle MECHANISTIC-EMPIRICAL ASPHALT OVERLAY THICKNESS DESIGN AND ANALYSIS SYSTEM 5. Report Date November 2008 Resubmitted: February 2009 Resubmitted: July 2009 Published: October 2009 6. Performing Organization Code 7. Author(s) Fujie Zhou, Sheng Hu, Xiaodi Hu, and Tom Scullion 8. Performing Organization Report No. Report 0-5123-3 9. Performing Organization Name and Address Texas Transportation Institute The Texas A&M University System College Station, Texas 77843-3135 10. Work Unit No. (TRAIS) 11. Contract or Grant No. Project 0-5123 12. Sponsoring Agency Name and Address Texas Department of Transportation Research and Technology Implementation Office P. O. Box 5080 Austin, Texas 78763-5080 13. Type of Report and Period Covered Technical Report: September 2007-August 2008 14. Sponsoring Agency Code 15. Supplementary Notes Project performed in cooperation with the Texas Department of Transportation and the Federal Highway Administration. Project Title: Development of an Advanced Overlay Design System Incorporating Both Rutting and Reflection Cracking Requirements URL: http://tti.tamu.edu/documents/0-5123-3.pdf 16. Abstract The placement of an asphalt overlay is the most common method used by the Texas Department of Transportation (TxDOT) to rehabilitate existing asphalt and concrete pavements. The type of overlay and its required thickness are important decisions that TxDOT engineers make on a daily basis. To perform well, an asphalt overlay must have a balance of both good rut and crack resistance. Furthermore, overlay performance is highly influenced by many factors, such as existing pavement conditions, traffic loading, and environmental conditions. It has also recently become common practice to use two different materials in an overlay, the first being a crack resistant level up course and the second being a wearing surface. The properties of both overlay types have a big impact on performance. The main objective of the Research Project 0-5123 was to develop a comprehensive mechanistic-empirical (M-E) asphalt overlay design system to assist TxDOT engineers to make these design decisions. The design system developed incorporates models for both rutting and reflection cracking of the proposed overlay. The Paris’ law-based reflection cracking model was evaluated and recommended for use in this study. This model requires the use of both stress intensity factors (SIF) and fracture properties (A and n) for predicting crack propagation caused by both traffic loading and thermal effects. For practical implementation of the SIF concept, a total of 34 SIF regression equations were developed based on more than 1.6 million finite element computations. The required fracture properties can be easily determined using the Overlay Tester. The proposed reflective cracking model was calibrated using performance data from three HMA overlay field case studies and then verified using the California’s Heavy Vehicle Simulator test results. To predict asphalt overlay rutting, the well-known VESYS layer rutting model was used and later calibrated using the field rutting data from the National Center for Asphalt Technology (NCAT) test track 2006. The material properties required for this model are obtained from repeated load tests. The reasonableness and accuracy of the calibrated rutting was further verified by the field rutting data from NCAT test track 2000. Finally, the calibrated reflective cracking and rutting models were integrated into an asphalt overlay thickness design and analysis program. To assist in implementation, default values of material properties have been provided for all the overlay types currently used in Texas. The program provides the designer with a tool to evaluate on a project-level basis the impact of load transfer efficiency (LTE) on predicted life and to determine what level of LTE must be repaired in order to achieve adequate performance. In summary this study has developed a comprehensive overlay thickness design and analysis system based on solid engineering principles. The software package developed in this study has been provided to TxDOT. Based on the evaluations made in this study its predictions appear rational and reasonable. This system is ready for state-wide pilot implementation. 17. Key Words Reflective Cracking, Rutting, Stress Intensity Factor, Overlay Test, Repeated Load Test, Asphalt Overlay Design 18. Distribution Statement No restrictions. This document is available to the public through NTIS: National Technical Information Service Springfield, Virginia 22161 http://www.ntis.gov 19. Security Classif.(of this report) Unclassified 20. Security Classif.(of this page) Unclassified 21. No. of Pages 154 22. Price Form DOT F 1700.7 (8-72) Reproduction of completed page authorized
MECHANISTIC-EMPIRICAL ASPHALT OVERLAY THICKNESS DESIGN AND ANALYSIS SYSTEM
Jun 27, 2023
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