evaluation of fatigue properties of asphalt mixtures containing reclaimed asphalt using response surface method

this paper presents the effects of different amounts of reclaimed asphalt on fatigue life of asphalt mixtures. central composite method was used to design of experiments based on response surface method (rsm). binder type (pen 60/70 and pen 85/100), reclaimed asphalt pavement (rap) content (25, 50 and 75%) and loading strain (150, 250 and 350 micro strain) were selected as independent variables, while 50% of initial stiffness, fatigue life and final stiffness of asphalt mixtures were chosen as dependent variables. in this research study, fatigue properties of asphalt mixtures were measured by using the four-point bending beam. the rsm analyses showed that all independent variables were significant factors for prediction of 50% of initial stiffness and fatigue life. in addition, analysis of the tests results showed that the mixtures containing higher amount of rap at lower strains, had higher final stiffness. furthermore, the fatigue life of specimens increased, when the level of test strains decreased. also at the lower level of loading strain, by increasing the rap content, the fatigue life was not decreased.