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Publication Number: FHWA-HRT-04-079
Date: July 2006

Seasonal Variations in The Moduli of Unbound Pavement Layers

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FOREWORD

The in situ moduli of unbound pavement materials vary on a seasonal basis as a function of temperature and moisture conditions. Knowledge of these variations is required for accurate prediction of pavement life for pavement design and other pavement management activities. The primary objective of this study is to advance the rational estimation of seasonal variations in backcalculated pavement layer moduli using data collected via the Seasonal Monitoring Program of the Long-Term Pavement Performance (LTPP) Program. Principal components of this endeavor included: evaluation of the moisture predictive capabilities of the Enhanced Integrated Climatic Model (EICM); development of empirical models to predict backcalculated pavement layer moduli as a function of moisture content, stress state, and other explanatory variables; and trial application of the models developed to prediction backcalculated moduli for unbound pavement layers.

This investigation yielded two key findings. First, it provided the impetus for developing EICM Version 2.6 by demonstrating the practical inadequacies of EICM Versions 2.0 and 2.1 when applied to the prediction of in situ moisture content, and then demonstrated that improvement in the moisture predictive capability of the EICM had been achieved in Version 2.6. Second, the research identified fundamental discrepancies between layer moduli backcalculated using linear layered-elastic theory and the laboratory resilient modulus test conditions.

Gary L. Henderson
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. This report does not constitute a standard, specification, or regulation.

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.

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Technical Report Documentation Page

 

1. Report No.

FHWA-HRT-04-079

2. Government Accession No.

3. Recipient's Catalog No.

4. Title and Subtitle

Seasonal Variations in the Moduli of Unbound Pavement Layers

5. Report Date

July 2006

6. Performing Organization Code

7. Author(s)

Cheryl Allen Richter

8. Performing Organization Report No.

9. Performing Organization Name and Address

Federal Highway Administration
6300 Georgetown Pike
McLean, VA 22101

10. Work Unit No. (TRAIS)

11. Contract or Grant No.

DTFH61–00–C–00121

12. Sponsoring Agency's Name and Address

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

13. Type of Report and Period Covered

Final Report
February 2000 to April 2004

14. Sponsoring Agency's Code

15. Supplementary Notes

Contracting Officer's Technical Representative: Aramis Lopez, HRDI - 13

16. Abstract

The in situ moduli of unbound pavement materials vary on a seasonal basis as a function of temperature and moisture conditions. Knowledge of these variations is required for accurate prediction of pavement life for pavement design and other pavement management activities. The primary objective of this study is to advance the rational estimation of seasonal variations in backcalculated pavement layer moduli using data collected via the Seasonal Monitoring Program of the Long-Term Pavement Performance Program. Principal components of this endeavor included: evaluation of the moisture predictive capabilities of the Enhanced Integrated Climatic Model (EICM); development of empirical models to predict backcalculated pavement layer moduli as a function of moisture content, stress state, and other explanatory variables; and trial application of the models developed to prediction backcalculated moduli for unbound pavement layers.

This investigation yielded two key findings. First, it provided the impetus for developing EICM Version 2.6 by demonstrating the practical inadequacies of EICM Versions 2.0 and 2.1 when applied to the prediction of in situ moisture content, and then demonstrated that substantial improvement in the moisture predictive capability of the EICM had been achieved in Version 2.6. Second, the research identified fundamental discrepancies between layer moduli backcalculated using linear-layered elastic theory and the laboratory resilient modulus test conditions.

Other important findings included (1) variation in moisture content is not always the most important factor associated with seasonal variations in pavement layer moduli, and (2) a model form that fits linear elastic backcalculated moduli reasonably well. The overall accuracy of the modulus predictions achieved in the trial application of the predictive models was not fully acceptable. Several avenues for further research to improve upon these results are identified.

17. Key Words

LTPP, Seasonal Monitoring Program, modulus, pavement, Enhanced Integrated Climatic Model, linear layered elastic theory

18. Distribution Statement

No restrictions. This document is available to the public through the National Technical Information Service, Springfield, VA 22161.

19. Security Classif. (of this report)

Unclassified

20. Security Classif. (of this page)

Unclassified

21. No. of Pages

283

22. Price

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

 

SI (Modern Metric) Conversion Factors

TABLE OF CONTENTS

  1. Introduction and Research Objectives
  2. Literature Review
  3. Data Acquisition and Assessment
  4. Evaluation of Volumetric Moisture Predictions From the Integrated Climatic Model
  5. Prediction of Backcalculation Pavement Layer Moduli
  6. Application of Research Results To Estimate Seasonal Variations in Moduli of Unbound Pavement Layers
  7. Conclusions and Recommendations

Appendix A. Variation in TDR Moisture Data

Appendix B. Input Data for the Enhanced Integrated Climatic Model

Appendix C. Between-user Differences in Application of EICM Version 2.6

Appendix D. Materials Data Used In Development of E Predictive Models

Appendix E. Multiple Regression Results for Individual Pavement Layers

Appendix F. Trial Application Results Based on Section/Layer-Specific Models Derived From All Available Data

Appendix G. Trial Application Results Obtained With One-date Section/Layer-Specific Models

Appendix H. Trial Application Results Obtained With Two-Date Section/Layer-Specific Models

Appendix I. Trial Application Results Obtained With Soil Class Models

References

LIST OF FIGURES

LIST OF TABLES

86FHWA-HRT-04-079

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The Federal Highway Administration (FHWA) is a part of the U.S. Department of Transportation and is headquartered in Washington, D.C., with field offices across the United States. is a major agency of the U.S. Department of Transportation (DOT).
The Federal Highway Administration (FHWA) is a part of the U.S. Department of Transportation and is headquartered in Washington, D.C., with field offices across the United States. is a major agency of the U.S. Department of Transportation (DOT). Provide leadership and technology for the delivery of long life pavements that meet our customers needs and are safe, cost effective, and can be effectively maintained. Federal Highway Administration's (FHWA) R&T Web site portal, which provides access to or information about the Agency’s R&T program, projects, partnerships, publications, and results.
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