Physically Based Model for Predicting the Susceptibility of Asphalt Pavements to Moisture-Induced Damage
Rashid K. Abu Al-Rub, Eyad A. Masad, and Michael A. Graham, Texas A&M University, September 2010, 73 pp. (476660-00012-1)
This study presents a novel moisture-induced continuum damage model for asphalt concrete. Moisture-induced damage is treated realistically as two mechanisms: (1) degradation of the adhesive bond between the asphalt mastic and aggregates and (2) degradation of the cohesive strength of the mastic. The moisture-induced damage model is formulated in a novel way, accounting for the gradual, irreversible degradation of a mix using continuum damage mechanics. Different mechanistic evolution laws are proposed for predicting adhesive and cohesive moisture-induced damage. To the authors’ best knowledge, this model is the first continuum model to capture all facets of realistic asphalt mix response. Moreover, a time- and rate-dependent damage constitutive law is proposed to predict crack nucleation and propagation due to different mechanical loading conditions. The moisture-induced and mechanically-induced damage models are integrated into a three-dimensional nonlinear viscoelastic-viscoplastic constitutive model to allow for more realistic prediction of damage evolution in asphalt concrete under various traffic and environmental loading conditions. Numerical integration algorithms are presented for implementing the model in the well-known finite element code Abaqus. Finally, various aspects of the integrated continuum damage mechanics model are investigated and found to match the qualitative behavior of experiments. The current moisture-induced damage model can be used by pavement engineers to predict the time frame over which moisture-induced damage may occur and to rank asphalt mixtures for moisture damage susceptibility.
Keywords: Moisture Damage Model; Adhesive Moisture Damage; Cohesive Moisture Damage; Viscoelasticity; Viscoplasticity; Finite Element
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