Page 431 - Mechanics of Asphalt Microstructure and Micromechanics

CHAPTER13

Multiscale Modeling and

Moisture Damage

13.1 Introduction
This chapter presents some recent developments on multiscale modeling and moisture
damage mechanisms of asphalt concrete (AC). These recent developments, to a certain
degree, are still at their inception stage.

13.2 Multiscale Characterization and Modeling

13.2.1 Needs for Multiscale Modeling
The mix design methods for AC are highly empirical. It usually involves testing a rep-
resentative volume (a specimen) of different blends to evaluate their properties and
applying macro-constitutive models and failure criteria to assess the behavior or per-
formance of these materials placed in the field at certain assumed conditions. Due to the
differences in size, pavement structure, environmental and loading conditions, and
complex coupling, lab specimen behavior may not reflect the field performance of the
mix. In addition, the mixing of these different components results in various complex
physical interactions, chemical reactions, and electromagnetic interactions. Since these
reaction processes have not been well understood, mixture properties are often not as
expected. Mix design often involves understanding chemical reactions where quantum
mechanics, chemomechanics, may play an important role in interpreting these complex
reaction processes and guiding mix design.
Asphalt concrete is highly heterogeneous, with components of significantly distinct
physical, chemical, thermal-mechanical, and electromagnetic properties. In addition, the
sizes of the particles range from nanometer to centimeter; the inherent and induced de-
fects have also a similar size range. The particle and defect at different sizes interact dif-
ferently and in a complicated manner. Traditional approaches in homogeneous continu-
um mechanics, micromechanics, continuum damage mechanics, and fracture mechanics
may be able to describe the behavior of these materials under complicated environmen-
tal and loading conditions in one scale, but fail to address the failure and interaction of
components and defects at different scales with significant heterogeneity. Multiscale
characterization, modeling, and simulation prove to be a useful tool. In addition, recent
developments in supercomputers and parallel computation make it realistically feasible

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