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Publication Number: FHWA-HRT-10-065
Date: December 2010

Modeling of Hot-Mix Asphalt Compaction: A Thermodynamics-Based Compressible Viscoelastic Model

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FOREWORD

This report details the activities and findings of research on mathematical modeling of compaction of hot-mix asphalt (HMA) pavements. The primary objective of this project was to develop a material model in a general mechanical setting to study the mechanics associated with asphalt mix compaction. The researchers developed a viscoelastic compressible fluidlike model, which was then adapted for simulating compaction of HMA employing the finite-element (FE) method. The model was developed within a thermodynamic framework that was capable of demonstrating the nonlinear dissipative response associated with the asphalt mix. This work should lead to further development of simulation models capable of capturing the mechanics of the compaction processes both in the laboratory and in the field.

The FE method was employed to simulate laboratory and field compaction under various loading and boundary conditions. The FE results agree well with the data obtained from various laboratory and field compaction projects. The field compaction results validate the applicability of the model to predict compaction in highway projects.

This study can be used by practitioners and researchers to design mixtures with desirable compaction characteristics and improved performance. The material presented here is the final report for the project.

Jorge Pagán-Ortiz
Director, Office of Infrastructure
Research and Development

Notice

This document is disseminated under the sponsorship of the U.S. Department of Transportation 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-10-065

2. Government Accession No. 3. Recipient’s Catalog No.

4. Title and Subtitle

Modeling of Hot-Mix Asphalt Compaction: A Thermodynamics-Based Compressible Viscoelastic Model

5. Report Date

December 2010

6. Performing Organization Code

C-00053

7. Author(s)

Eyad Masad, Saradhi Koneru, Tom Scarpas, Emad Kassem, and K.R. Rajagopal

8. Performing Organization Report No.

DTFH61-07-C-00053-F-10-01

9. Performing Organization Name and Address

Texas Transportation Institute
The Texas A&M University System
College Station, TX 77845-3135

10. Work Unit No. (TRAIS)

11. Contract or Grant No.

DTFH61-07-C-00053

12. Sponsoring Agency Name and Address

Office of Acquisition Management
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590-0001

13. Type of Report and Period

Final Report
November 2007–May 2010

14. Sponsoring Agency Code

HAAM-30

15. Supplementary Notes

This project was completed in coordination with Eric Weaver from FHWA by researchers at Texas A&M University and researchers at the Section of Structural Mechanics, Civil Engineering and Geosciences, Delft University of Technology, The Netherlands.

16. Abstract

Compaction is the process of reducing the volume of hot-mix asphalt (HMA) by the application of external forces. As a result of compaction, the volume of air voids decreases, aggregate interlock increases, and interparticle friction increases. The quality of field compaction of HMA is one of the most important elements influencing asphalt pavement performance. Poor compaction has been associated with asphalt bleeding in hot weather, moisture damage, excessive aging and associated cracking, and premature permanent deformation.

 

This study was conducted to develop a model within the context of a thermomechanical framework for the compaction of asphalt mixtures. The asphalt mixture was modeled as a nonlinear compressible material exhibiting time-dependent properties. A numerical scheme based on finite elements was employed to solve the equations governing compaction mechanisms. The material model was implemented in the Computer Aided Pavement Analysis (CAPA-3D) finite-element (FE) package. Due to the difficulty of conducting tests on the mixture at the compaction temperature, a procedure was developed to determine the model's parameters from the analysis of the Superpave® gyratory compaction curves. A number of mixtures were compacted in the Superpave® gyratory compactor using an angle of 1.25 degrees in order to determine the model's parameters. Consequently, the model was used to predict the compaction curves of mixtures compacted using a 2-degree angle of gyration. The model compared reasonably well with the compaction curves. FE simulations of the compaction of several pavement sections were conducted in this study. The results demonstrated the potential of the material model to represent asphalt mixture field compaction.

 

The developed model is a useful tool for simulating the compaction of asphalt mixtures under laboratory and field conditions. In addition, it can be used to determine the influence of various material properties and mixture designs on the model's parameters and mixture compactability.

17. Key Words

Compaction, Hot-mix asphalt, Mixture design, Constitutive model, Finite element, Simulation, Viscoelastic, Compressible

18. Distribution Statement

No restrictions. This document is available to the public through the National Technical Information Service, Alexandria, VA 22312.

19. Security Classif. (of this report)

Unclassified

20. Security Classif. (of this page)
Unclassified

21. No. of Pages

110

22. Price

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

SI* (Modern Metric) Conversion Factors

TABLE OF CONTENTS

CHAPTER 1. INTRODUCTION

CHAPTER 2. REVIEW OF THE LITERATURE

CHAPTER 3. A THERMOMECHANICAL MODEL FOR ASPHALT CONCRETE

CHAPTER 4. NUMERICAL IMPLEMENTATION IN THE FE METHOD

CHAPTER 5. FE SIMULATION OF SGC COMPACTION

CHAPTER 6. FE SIMULATION OF FIELD COMPACTION

CHAPTER 7. SIMULATION OF FIELD COMPACTION

CHAPTER 8. SUMMARY AND CONCLUSIONS

REFERENCES

LIST OF FIGURES

LIST OF TABLES

LIST OF ABBREVIATIONS

%AV Percent air void
CAPA-3D Computer Aided Pavement Analysis
FE Finite-element
FHWA Federal Highway Administration
HMA Hot-mix asphalt
IC Intelligent compaction
PG Superpave® performance grading
SGC Superpave® gyratory compactor
VMA Void in the mineral aggregate