Page 23 - MODELING OF ASPHALT CONCRETE

CHAPTER 1

Modeling of

Asphalt Concrete

Y. Richard Kim

Introduction
Asphalt concrete pavement, one of the largest infrastructure components in the United
States, is a complex system that involves multiple layers of different materials, various
combinations of irregular traffic loading, and varying environmental conditions.
Therefore, a realistic prediction of the long-term service life of asphalt pavements is
one of the most challenging tasks for pavement engineers. The performance of asphalt
concrete pavements is closely related to the performance of asphalt concrete. It is
performance models of asphalt concrete that provide the links among various
processes involved in asphalt mixture design, pavement design, construction, and
rehabilitation.
Various factors affect the deformation behavior and performance of asphalt concrete,
including time (i.e., rate of loading, loading time, rest period), temperature, stress state,
mode of loading, aging, and moisture. Models have been developed to capture the
effects of these factors on asphalt concrete performance. Most of these models,
developed prior to the Strategic Highway Research Program (SHRP), are empirical in
nature. The primary reason for the empirical nature of these models is the lack of
computing power necessary to calculate the long-term performance of asphalt concrete
and, therefore, asphalt pavements. The SHRP recognized the importance of mechanistic
models for material specifications, mixture design, and pavement design and developed
a range of research products based on the principles of mechanics. The paradigm shift
from empiricism to mechanics during the SHRP made a significant impact on the role
of models in asphalt pavement engineering.
Development of a fundamentally sound performance model serves two important
purposes. For pavement engineers, such a model can provide accurate information
about the performance of asphalt concrete under realistic loading conditions, thus
leading to a better assessment of the service life of a new pavement or the remaining life
of an existing pavement. For materials engineers, the performance model founded on

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