Assessing the Role of Phase Angle in Enhancing the Fatigue Life and Deformation of Asphalt Concrete under Environmental Influence

Abstract

The Asphalt concrete mixtures exhibit changes in their physical properties under various loading periods and thermal conditions while they can reveal their rheological characteristics. The accumulation of deformation and the fatigue life of asphalt concrete depend on its durability; however, the variation in the environmental conditions can enhance the deformation resistance and the fatigue life of the flexible pavement. In the present assessment, the influence of variation in the phase angle of asphalt concrete on its resistance to deformation and the fatigue life under environmental influence have been investigated. Asphalt concrete mixtures were prepared at its optimum binder requirements, and then compacted into a slab mold by laboratory roller to a target density. Beam specimens were obtained from the prepared slab samples and tested for fatigue life using three levels of constant strain of (750, 400, and 250) microstrain under dynamic flexural stresses. The specimens were tested at (30, 20, and 5) ℃ environment levels. It was noticed that longer fatigue life could be noticed as the testing temperature increases, and more elapsed time is consumed to create the deformation as the testing temperature increase. The fatigue life from the phase angle point of view increases as the testing temperature rises. The phase angle at failure decline from (70 to 30 and 25) ˚ when the constant strain level decline from (750 to 400 and 250) microstrain respectively. It was concluded that at lower constant strain levels of (400, and 250) microstrain, the phase angle increases as the testing temperature rises. Higher testing environment increases the fatigue life, and changes the mode of failure of asphalt concrete from brittle to plastic mode.