Page 161 - MODELING OF ASPHALT CONCRETE

CHAPTER 6

Interrelationships

among Asphalt Concrete

Stiffnesses

Ghassan R. Chehab and Y. Richard Kim

Abstract
The chapter discusses the three major response functions used for characterizing the
linear viscoelastic behavior of asphalt concrete mixtures. Definitions and analytical
representations of those functions: creep compliance, relaxation modulus, and complex
modulus, are presented. Methods for the determination of the functions’ analytical
parameters through experimental tests are introduced. Additionally, numerical and
analytical interconversion techniques to determine one LVE response function from the
other are also presented and compared. Numerical examples and plots are included to
supplement the methodologies presented.

Introduction
Asphalt concrete exhibits time/rate dependence, where the material response is not
only a function of the current input, but also of the current and past input history. When
the loading conditions do not cause damage to the asphalt mixture, the response could
be defined as linear viscoelastic and expressed through the convolution (hereditary)
integral. While viscoelasticity is typically associated with a system’s time-dependent
response, linearity is associated with systems where the conditions of homogeneity and
superposition are satisfied:
Homogeneity: R {AI} = A R {I} (6-1)
Superposition: R {I + I } = R {I } + R {I } (6-2)
1 2 1 2
where I, I , I = input histories
1 2
R = response
A = arbitrary constant

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