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Publication Number:  FHWA-HRT-99-144    Date:  June 2001
Publication Number: FHWA-HRT-99-144
Date: June 2001


Microdamage Healing in Asphalt and Asphalt Concrete, Volume IV: A Viscoelastic Continuum Damage Fatigue Model of Asphalt Concrete With Microdamage Healing

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A mechanistic approach to fatigue characterization of asphalt-aggregate mixtures is presented in this I volume. This approach is founded on a uniaxial viscoelastic constitutive model that accounts for damage I evolution under cyclic loading conditions. The elastic-viscoelastic correspondence principle is applied in I order to evaluate damage growth and healing in cyclic loading separately from time-dependent characteristic I of the material. The damage growth during loading cycles and healing during rest periods are modeled using work potential theory, a continuum damage theory based on thermodynamics of irreversible processes. I Internal state variable formulation was used in developing the analytical representation model. Tensile I uniaxial fatigue tests were performed in the controlled-strain mode with different strain amplitudes to determine model parameters. The resulting constitutive model successfully predicts the damage growth of I asphalt concrete under monotonic loading at varying strain rates and damage growth and recovery due to complex loading histories, in both controlled-strain and controlled-stress modes, composed of randomly applied multi-level loading with different loading rates and varying durations of rest.

Fatigue lives of two different mixtures were predicted with reasonable accuracy using the constitutive I model for the constant stress-strain amplitude cyclic loading histories with and without rest periods. A standard uniaxial fatigue test protocol is proposed by simplifying the experimental approach used in developing the constitutive model.



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