Temperature effect on the failure mechanism of fatigue life in rejuvenated RAP bitumen utilizing LAS method and PSE S-VECD model

The linear amplitude sweep (LAS) test is esteemed as an effective tool for assessing bitumen fatigue performance. Utilizing a pseudo-strain energy (PSE) based failure analysis, this research investigated the impact of temperature on the failure mechanism of rejuvenated RAP bitumen’s fatigue resistance using the LAS test. Based on a PSE simplified viscoelastic continuum damage (S-VECD) approach, the analysis results revealed that the flow failure mechanism rather than cohesive failure would be dominant, once the dynamic shear moduli (|G*|) were selected above a certain critical temperature. Similarly, at intermediate and enough low temperatures, adhesive and cohesive failures, respectively, between the bitumen samples and DSR palates is found to confound results. Considering that the actual test procedure does not specify the testing temperature, it is necessary to assess the failure mechanism to verify test results and prevent inconsistent outcomes. Accordingly, the temperature should be selected carefully once the |G*| falls within the range of 9–55 MPa to avoid confounding impacts of adhesion loss and flow. Based on this finding, time-temperature superposition was utilized to PSE S-VECD results and fatigue life trends with temperature variations illustrated to be bitumen dependent. Observations from the simplified approach revealed a very strong correlation with the measured fatigue life of rejuvenated RAP bitumen. •Explored the impact of temperature on the fatigue life (Nf) of rejuvenated RAP bitumen mixes.•Introduced failure mechanism types to guide the selection of testing temperature.•Investigated the utilization of pseudo-strain within the S-VECD model to analyze LAS results.•Introduced a simplified method for predicting bitumen Nf at cohesive temperatures.•Explored two failure criteria for determining bitumen Nf in the new prediction approach.