Page 8 - Mechanics of Asphalt Microstructure and Micromechanics

CHAPTER1

Introduction and Fundamentals

for Mathematics and

Continuum Mechanics

1.1 General Introduction
In this chapter, the fundamental properties that make asphalt concrete (AC) different
from other materials are discussed. Logically, this discussion will serve as the guiding
principles for the entire book.
Asphalt concrete is a unique material in four aspects: 1) its composition; 2) its
manufacturing process; 3) its use environment; and 4) its performance or failure
modes. These unique characteristics make AC different from other materials, and
make this book valuable and uncommon. There are many textbooks on the mechanics
of different materials and many books on the general topics of mechanics as well.
What makes AC different from other materials is addressed in detail and serves as the
focus of this book.

1.1.1 Unique Material Structure and Complexity
AC consists mainly of three constituents: asphalt binder, aggregates, and air voids. Oth-
er constituent/constituents may include additives such as fillers, modifiers, and fibers.
These constituents are often used to enhance the properties of AC for specific aspects,
such as moisture damage. The three major constituents have great differences in their
properties and variety. While most of the binders are residuals of petroleum refinery,
different petroleum resources and refining procedures will end up with binders of dif-
ferent molecular structure and compositions. Aggregates come with a variety of miner-
als that have different reactions with binders. The stiffness of the three constituents is so
drastically different that tremendous localizations make properties of this material
highly variable. While there are other distinct properties, three important properties of
binder—thermal sensitivity, loading rate sensitivity, and moisture sensitivity—make
this material much more challenging than most other materials in characterization,
modeling and simulation, and especially predicting its behavior or performance under
complex use environments including temperature, loading magnitude, and loading
rates. The unique material structure and complexity requires a microscopic view.

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