Incorporating temperature into the constitutive equation for plastic deformation in asphalt binders

Predicting the permanent deformation in asphalt binders under service load is an important step towards selecting the most appropriate asphalt binder for a flexible pavement. A model to predict the permanent strain in asphalt binders as a function of load duration and stress level at a constant temperature was developed in previous studies. In this approach, total strain was predicted as the summation of permanent and recoverable strain. This paper investigates the effect of temperature as an additional factor in this model. Considering the Arrhenius equation as the governing physicochemical rate process equation of many materials, it was hypothesized that temperature can be considered as an independent correction factor for permanent strain. This was verified by conducting a full factorial design and obtaining the interaction between temperature and other main factors. The significance of the factors was also computed to determine which factors should be incorporated in the prediction model. Analysis of the creep test results at different temperatures showed that the total strain under step loading follows the time-temperature superposition. Therefore, the recoverable strain in asphalt binders under a step loading at any given temperature can be predicted using the time-temperature superposition and Arrhenius equation. The model for prediction of the asphalt binder response was extended to include temperature as an additional factor. The extended model was verified under different loading conditions. This model will help engineers to better understand the rheology of asphalt binder and choose an appropriate asphalt binder based on traffic and environmental conditions. (C) 2011 Elsevier Ltd. All rights reserved.