Page 227 - MODELING OF ASPHALT CONCRETE

CHAPTER 8

Unified Disturbed State

Constitutive Modeling

of Asphalt Concrete

Chandrakant S. Desai

Abstract
Although the need for mechanistic and unified constitutive models for pavement
materials has been identified, such models are yet not readily available. Some unified
approaches have been proposed; however, they are often based on ad hoc combinations
of models for specific properties such as elastic, plastic, creep, and fracture. Such
approaches do not provide appropriate connections to coupled responses in the bound
and unbound materials. They often involve larger number parameters, sometimes
without physical meanings. The disturbed state concept (DSC), presented in this chapter,
provides a modeling procedure that includes the coupled response including such
factors as elastic, plastic, and creep stains, microcracking and fracture, softening and
healing under mechanical and environmental (thermal, moisture, etc.) loadings. It is
based on a single unified and coupled framework, and can be applied to both solids
(bound and unbound materials) and interfaces and joints. A brief review of various
available approaches is presented and the differences and advantages of the DSC are
identified. The DSC has been validated and applied to a wide range of materials such as
soils, rocks, concrete, asphalt concrete, ceramics, alloys (solders), and silicon; in this
chapter, it is directed toward modeling of asphalt concrete. The DSC allows evaluation
of various distresses such as permanent deformation (rutting), microcracking and
fracture, reflection cracking, thermal cracking, and healing. It has been implemented in
two- and three-dimensional (2-D and 3-D) finite element (FE) procedures, which allow
static, repetitive, and dynamic loadings. In the hierarchical scheme, DSC allows selection
of various versions such as elastic, plastic, creep, microcracking leading to fracture and
failure, depending on the need of the user. A number of examples are solved for various
distresses considering flexible (asphalt) pavements; however, the DSC model is applicable
to rigid (concrete) pavements also. It is believed that the DSC can provide a unified and

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