Effects of Recycled Asphalt Pavement on the Stiffness and Fatigue Performance of Multigrade Bitumen Asphalt

Recycled asphalt pavement (RAP) has received considerable interest in recent years for economic, environmental, and social reasons, and it is necessary to discover what effect the inclusion of RAP into asphalt layers has on the fatigue life of a pavement. Multigrade bitumen is less sensitive to temperature compared with conventional bitumen; therefore, it is expected that multigrade bitumen asphalt will perform much better than conventional asphalt. It is important to investigate the performance of RAP-added multigrade bitumen asphalt as an innovative pavement material. Therefore, in this study the effects of multigrade bitumen types and the amount of RAP content (e.g.,0 and 15%) on the fatigue life of this innovative pavement material were investigated in the laboratory using a four-point beam fatigue testing apparatus under controlled temperature. The results suggested that multigrade bitumen asphalt with and without RAP has higher fatigue life compared with the conventional bitumen asphalt. Further, it was revealed that the type of multigrade bitumen has significant effects on the fatigue performance of multigrade bitumen asphalt. It was observed that the effect of the RAP on the fatigue performance of multigrade bitumen varies with the type of multigrade bitumen. The study was further expanded to develop a master curve for a given mixture and the master curve can be used to obtain flexural modulus of the mixture at a given temperature and at a given loading frequency. The results show that multigrade bitumen and RAP inclusion can have beneficial effects on pavement design thickness.