Investigating the properties of recycled asphalt concrete modified by nano-silica and rejuvenated by waste cooking and engine oil

Using recycled asphalt mixtures, which are made by waste materials, have attracted attentions due to their environmental and economical benefits. However, challenges exist with the performance of the recycled mixtures. In this study, the effect of using nano-silica on the behavior of non-rejuvenated and rejuvenated recycled asphalt concrete has been investigated. Penetration grade asphalt binder modified by 5% of nano-silica has been used in recycled asphalt concrete containing 60% of reclaimed asphalt pavement (RAP). The mixture without rejuvenation and rejuvenated by a constant percentage of waste cooking oil and waste engine oil has been evaluated by indirect tensile strength test on dry and moisture conditioned samples, dynamic creep test and stress controlled fatigue test. The properties of the mixtures have been compared with each other and with the control mixture made by neat binder and aggregates. The tests have been conducted on the samples before aging and after undergoing long term aging condition to investigate the effect of aging on the properties. Results reveal that incorporating RAP into the mixture increases the tensile strength, resistance against creep and fatigue and decreases the moisture resistance of the mixture. Nano-silica modification increases the dry and conditioned tensile strength, resistance against permanent deformation and fatigue. Nano-silica also improves aging resistance of the recycled mixtures. Furthermore, results reveal that waste oils as rejuvenator improves moisture resistance of the mixtures with more improvement for waste cooking oil. In addition, the effect of aging on the properties of the mixture rejuvenated by waste cooking oil is higher than those rejuvenated by waste engine oil.