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
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The U.S. Government does not endorse products or manufacturers.
Trademarks or manufacturers’ names appear in this report only
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document.
Quality Assurance Statement
The Federal Highway Administration (FHWA) provides high-quality
information to serve Government, industry, and the public in a
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1. Report No.
FHWA-HRT-04-079
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2. Government Accession No.
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3. Recipient's Catalog No.
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4. Title and Subtitle
Seasonal Variations in the Moduli of Unbound Pavement Layers
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5. Report Date
July 2006
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6. Performing Organization Code
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7. Author(s)
Cheryl Allen Richter
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8. Performing Organization Report No.
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9. Performing Organization Name and Address
Federal Highway Administration
6300 Georgetown Pike
McLean, VA 22101
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10. Work Unit No. (TRAIS)
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11. Contract or Grant No.
DTFH61–00–C–00121
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12. Sponsoring Agency's Name and Address
Office of Infrastructure Research and Development
Federal Highway Administration (FHWA)
6300 Georgetown Pike
McLean, VA 22101
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13. Type of Report and Period Covered
Final Report
February 2000 to April 2004
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14. Sponsoring Agency's Code
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15. Supplementary Notes
Contracting Officer's Technical Representative: Aramis Lopez,
HRDI - 13
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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.
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17. Key Words
LTPP, Seasonal Monitoring Program, modulus, pavement, Enhanced
Integrated Climatic Model, linear layered elastic theory
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18. Distribution Statement
No restrictions. This document is available to the public
through the National Technical Information Service, Springfield, VA
22161.
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19. Security Classif. (of this report)
Unclassified
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20. Security Classif. (of this page)
Unclassified
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21. No. of Pages
283
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22. Price
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