Predicting the Fatigue Life of Reinforced Asphalt with PET Fibers Based On Dissipated Energy Parameters at Variable Temperature and Frequency

This research investigated the possibility of predicting the fatigue life of reinforced asphalt by recycled polyethylene terephthalate (PET) fibers based on dissipated energy parameters. Fatigue tests were performed using 4-point bending test at three temperatures of -5, 10 and 20oC and two frequencies of 10 and 2 Hz. Fibers were incorporated at two lengths of 1 and 2 cm and average diameter of 30 micrometer. Furthermore, four fiber contents including 0.5, 1.0, 1.5 and 2.0% by weight of bitumen were used. Obtained fatigue laws showed an increase by increasing the test temperature. At a constant frequency, the fatigue lives of reinforced specimens were higher than the reference one. The beneficial effects of fibers were more pronounced at higher temperature and lower initial strain levels. Traditional fatigue models used the initial dissipated energy or cumulative dissipated energy to predict fatigue life. In newly established models the plateau value (PV1) parameter has been defined using the ratio of dissipated energy changes in plateau stage of dissipated energy curve obtained from 4-point fatigue test. In this research a new definition was presented to calculate the PV parameter (PV2). Based on statistical analysis power functions were presented to predict fatigue life based on PV1 and PV2 parameters. The relationships between PV and fatigue life was unique independent of the mix type and testing conditions (i.e. temperature, frequency and strain level). Furthermore, the fatigue model based on PV2 parameter was as precise as that presented using PV1.