Microdamage Healing in Asphalt and Asphalt Concrete; Volume IV: A Viscoelastic Continuum Damage...

Publication No. FHWA-RD-98-144

Volume IV presents a mechanistic approach to fatigue characterization of asphalt-aggregate mixtures. This approach is founded on a uniaxial viscoelastic constitutive model that accounts for damage evolution under cyclic loading conditions. The elastic-viscoelastic correspondence

principle is applied to evaluate damage growth and healing cyclic loading separately from time-dependent characteristics 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 the thermodynamics of irreversible processes). Internal state variable formulation was used in developing the analytical representation model. Tensile 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 asphalt concrete under monotonic loading at varying strain rates and damage growth.

The fatigue lives of two different mixtures were predicted with reasonable accuracy using the constitutive 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.

The NTIS publication number is PB2001-107669.