Relationship between backcalculated dynamic modulus, estimated dynamic modulus, and fatigue damage in asphalt concrete

ABSTRACT

There are several methods for determining the stiffness of asphalt concrete in an existing pavement. The three primary methods are dynamic modulus testing in the laboratory, predictive equations, and falling weight deflectometer (FWD) testing. The Pavement ME asphalt over asphalt (AC/AC) overlay design procedure uses multiple methods to characterise fatigue damage in the existing asphalt concrete. This paper examines the relationship between backcalculated dynamic modulus, estimated dynamic modulus, and fatigue damage in in-situ asphalt concrete. FWD load magnitude and asphalt temperature, both of which have been shown to affect the relationship between backcalculated and estimated dynamic modulus, are also considered. A statistical analysis is performed using data from the Long-Term Pavement Performance Programme (LTPP). Analyses are performed within individual LTPP sections and using pooled data from multiple pavement sections. It is determined that the relationship between backcalculated dynamic modulus and estimated dynamic modulus is significantly related to the amount of fatigue damage in the in-situ asphalt concrete. However, there is also a threshold of fatigue damage above which the relationship between backcalculated modulus, estimated modulus, and fatigue damage is no longer significant.

KEYWORDS:

• Asphalt concrete
• asphalt concrete overlay
• falling weight deflectometer
• fatigue damage
• Witczak equation

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Notes on contributors

N. Bech

Nathan Bech graduated from the University of Pittsburgh in 2018 with a M.S. in Civil Engineering. His thesis focused on the use of falling weight deflectometer testing in the Pavement ME AC/AC overlay design procedure. He is currently employed as a project engineer at ARRB Systems Americas in Exton, Pennsylvania, where he manages processing and analysis of structural and functional pavement data. His primary interest is applying traffic speed deflectometer testing at multiple scales: from single projects to state-level networks. Nathan is a member of the TRB Standing Committee on Pavement Condition Evaluation.

J. M. Vandenbossche

Julie Vandenbossche, Ph.D., P.E., is a Professor of Civil Engineering at the University of Pittsburgh. Her primary research interests are in the areas of concrete pavements, predictive performance modelling, concrete fatigue, and dowel bar performance. Dr. Vandenbossche is a recognised expert in structural modelling, evaluation, and performance prediction of concrete pavements. She served as a Principal or co-Principal Investigator on many high-profile research projects sponsored by the National Science Foundation, Department of Energy, National Academy of Science, Federal Highway Administration, and state transportation agencies with funding more than $11 million. She is a current member of University of Pittsburgh Senate Elections Committee and the Transportation Research Board Representative. She serves as an Associate Editor of American Society of Civil Engineers Journal of Transportation and an Editorial Board Member of Road Materials and Pavement Design and the International Journal of Pavement Research and Technology. Dr. Vandenbossche is a founding member of the Centre for Impactful Resilient Infrastructure Science and Engineering (IRISE). Her papers received awards from the Transportation Research Board and American Society of Civil Engineers.