Prediction of rut depth in asphalt pavement sections using permanent deformation shift model and stress sweep rutting test

The Stress Sweep Rutting (SSR) test is an experimental method used to evaluate asphalt mixtures’ resistance to permanent deformation. In the experiment, variables such as deviatoric stress level, loading time, and temperature are systematically varied. The results are ultimately used to develop a so-called shift model, which is a semi-empirical model that utilises the phenomenon of time-temperature-stress superposition to establish a single function capturing the effects of factors included in the SSR test. This shift model has been integrated into the pavement performance prediction programme, FlexPAVE™, to predict the permanent deformation of asphalt layers under various conditions as a function of pavement depth and time. This study presents modifications to the SSR test and the shift model, enhancing the accuracy of the asphalt pavement permanent deformation characterisation. These modifications have been incorporated into the FlexPAVE programme. Compared with the original equivalent area method, the proposed linear equation method resulted in less than a 10% difference in predicted rut depth after 20 years of service, while requiring only one-fifth of the computation time. A comparison between measured field data and the updated FlexPAVE predictions indicates no statistically significant difference between the predicted and measured pavement rut depths.