Investigation on fatigue damage of asphalt mixture with different air-voids using microstructural analysis

Fatigue damage caused by vehicle loads is the main asphalt pavement distress, and it deteriorates the serviceability and strength seriously. In order to evaluate the fatigue damage of asphalt mixture under repeated load, microstructures were detected to investigate the morphology change of internal structures using Digital Image Processing (DIP). Field pavement named as ISAC test track was built, and cores were drilled to slice into test specimens with different air-voids that can reflect the real internal state of asphalt pavement. Fatigue properties were measured under temperature −10 °C, 0 °C and 10 °C respectively, the frequency of sinusoid load was 0.1 Hz, the minimum value was 0.035 MPa and maximum value was 0.5 MPa. Internal structures of asphalt mixture were scanned by X-ray Computed Tomography (XCT) device before and after fatigue damage, thus the relationship between microstructures and fatigue damage can be conducted. The results show that microstructural analysis can effectively determine the internal structure change of asphalt mixture. Charging compaction causes different air-voids distributions and morphologies, which have obvious influence on failure state of asphalt mixture. The effect of temperature and initial air-voids on fatigue performance is significant, and fatigue damage presents a linear relation with the complexity of air-voids. Methodology established in this paper provides an effective method for fatigue damage assessment.