Developing laboratory fatigue and resilient modulus models for modified asphalt mixes with waste plastic bottles (PET)

Fatigue cracking is considered as a major failure in asphalt pavements. Hence, knowledge about the fatigue behavior of asphalt mixes will be important in designing of flexible pavements. There is limited information about the fatigue properties of modified mixes with waste plastic bottles (PET). In this study stiffness and fatigue behavior of PET modified mixes were evaluated at two testing temperatures of 5 and 20 °C. Different amounts of PET (2–10% by mass of bitumen) were incorporated to asphalt mixture using dry mixing method. The main goal of this study was to develop fatigue and resilient modulus models for studied mixes. Laboratory results showed that the fatigue life of asphalt mixes depends on the initial strain. The slope of fatigue curves decreased as a result of temperature decrease. At more than 210 microstrain, fatigue life decreased by increasing resilient modulus, whereas below 210 microstrain the reverse was true. On the basis of experimental analysis distinct fatigue models were developed for higher and lower strain levels of 210 microstrain, separately. In these models, fatigue life was related to initial strain and stiffness. Moreover, a model was developed to predict the resilient modulus of PET modified mixes based on the indirect tensile strength and testing temperature.