An evaluation proposal for the fatigue and healing performances of high-viscosity polymer-modified bitumen based on continuous multiple linear amplitude sweep

Due to the excellent shear deformation resistance of high-viscosity polymer-modified bitumen (HVPMB), the traditional methods based on time sweep and linear amplitude sweep (LAS) had problems with insufficient damage accumulation and inability to disrupt the integrity of HVPMB, making it difficult to accurately evaluate its fatigue and healing characteristics. To solve this problem, this study developed an effective evaluation proposal called continuous multiple LAS (MLAS) test and MLAS-based healing (MLASH) test. One base bitumen and three HVPMBs were selected for related experiments. MLAS test results confirmed that the percentage of strain energy attenuation (PSEA) can be used to evaluate the fatigue damage degree of HVPMBs. The lower the PSEA, the lesser damage. Combined with the fluorescence microscope and direct photography observation, the fatigue hairline cracks during MLAS test gradually expanded from the sample periphery to center until completely destroyed. Further, the MLASH test was developed to evaluate the healing performance of HVPMB by introducing intermittent duration into MLAS test. The variation of PSEA after tenth LAS loading (i.e. Delta PSEA) was proposed to evaluate the healing performance of HVPMB. The larger the Delta PSEA, the better the healing performance of HVPMB. All HVPMBs showed satisfactory healing performance once there was sufficient healing intermittent time (e.g. 180 s), and the healing performance was negatively correlated with the damage degree. Notably, the polymer structures had a dual effect on the healing performance of HVPMB, that is, they promoted the elastic healing recovery of HVPMB at lower temperature, while hindering the flow healing recovery at higher temperatures. Moreover, different temperatures caused a shift in the ranking of healing performance of various HVPMBs, thus the healing result at only single temperature cannot comprehensively represent the healing performance of HVPMB. Overall, the newly developed evaluation proposal can help to select HVPMB with excellent fatigue resistance and healing properties and provide a certain basis for accurately predicting HVPMB pavement life.