Development and Validation of a Nonlinear Model for Predicting Asphalt Concrete Rutting

Rutting in asphalt concrete (AC) is one of the main distresses in flexible pavements, so it is necessary to characterize AC behavior accurately. Viscoelastic fluid models, such as the Burger model, can characterize AC deformation behavior effectively. This study used a conventional Burger model, containing a nonlinear power-law dashpot, to model AC deformation behavior. An incremental formulation of the model was derived to obtain the deformation for arbitrary loading cases. First, a one-dimensional (1D) formulation, representing uniaxial stress–strain behavior, was first derived. The derivation was extended to a three-dimensional (3D) model using principles of linear elastic formulation. In addition, important components, such as stress increments and the Jacobian, were derived to be implemented into Abaqus software as a user subroutine. An analytical solution for a simple creep loading setup was used to verify the model’s implementation in Abaqus. The model parameters were obtained from the AC flow number and dynamic modulus tests. Dashpot parameters, a and b, were accurately and efficiently determined by leveraging the uniaxial stress condition in the flow number test and correlating it with the analytical solution. Sensitivity analysis showed that permanent strain (ϵp) was more influenced by b at lower temperatures, while a became slightly more dominant at higher temperatures. Additionally, a was independent of stress level, whereas b depended linearly on stress level. The model’s effectiveness was validated with experimental data. It was able to predict AC deformation accurately across various stress levels. This study highlights the simplicity of nonlinear dashpots over conventional models in capturing AC permanent deformation behavior.