Detecting the Variations in the Phase Angle through the Fatigue Life of Asphalt Concrete under Environmental Influence

The Asphalt concrete mixtures may exhibit changes in their mechanical behavior through the variation in environmental conditions and sustained loading time which enhances their fatigue life.In the present work, the role of the variations in the phase angle of the asphalt concrete on its fatigue life under three constant micro strain levels of (750, 400, and 250) microstrain to simulate the actual loading of the pavement in the field (heavy, moderate and low traffic volume) when experiences various environmental conditions of (5, 20, and 30) ℃ have been assessed.Asphalt concrete mixtures were prepared using its optimum binder requirements, and then experienced laboratory roller compaction into a slab mold to a target density.Beam specimens were extruded from the prepared slab samples and tested using dynamic flexural stresses for fatigue life.It was noticed that longer fatigue life could be achieved at high testing temperature, and more sustained time is consumed to resist the deformation.The fatigue life from the phase angle point of view increases as the testing temperature rises.It was noted that the phase angle at failure declines by (2.5, and 62.5) %, (16.6, and 58.4) %, and (6.2, and 85.4) % when the testing environment decline from (30 to 20 and 5) ℃ respectively under (250, 400, and 750) constant microstrain levels respectively.The fatigue life increases by (2.3, and 3.1) folds, (7.1, and 11.5) folds, and (32.3, and 39) folds when the testing temperature rises from (5 to 20 and 30) ℃ under (heavy, moderate, and low) traffic loading respectively.It can be revealed that the phase angle decline in general as the constant strain level increase for any specific testing environment and the fatigue life from the phase angle point of view increases as the testing temperature rises and decline as the constant strain level increase.