A unified thermally activated viscoplastic framework for bitumen failure prediction across various loading paths

Abstract

Accurately characterizing bitumen failure under combined thermal and mechanical stresses is key to designing durable pavement systems. This study proposes a unified, physically based framework that incorporates two thermally activated models to characterize the degradation behavior of bitumen. Eyring's stress-assisted molecular flow theory is applied to capture the nonlinear viscoplastic flow behavior under sustained loading, while a modified Arrhenius formulation expressed as a function of stress and temperature is utilized to mechanistically predict failure time. All model parameters are calibrated exclusively using constant-stress creep tests and are subsequently applied without any additional fitting to predict both the evolution of viscoplastic strain and the failure time under strain- and stress-controlled monotonic shear loading tests. Validation across a broad temperature spectrum confirms the model's high accuracy and indicates that viscoplastic deformation and failure are controlled by a common thermally activated mechanism, largely unaffected by the loading path. Minor deviations observed at elevated temperatures indicate the presence of self-healing behavior, suggesting a potential direction for future model refinement. Overall, the proposed framework provides a scalable, mechanistically interpretable, and experimentally efficient approach for reliable binder performance evaluation and performance-based material design.