Laboratory study of the effect of oil-based recycling agents on high RAP asphalt mixtures

Environmental issues and high prices of bitumen justify the use of reclaimed asphalt pavement (RAP) as a raw material in asphalt production. However, the high stiffness of the aged bitumen in RAP material often causes different problems such as lower workability and lower fatigue and cracking resistance which can be solved by using recycling agents (RA). In this research study, asphalt mixtures containing 0%, 25%, 50%, 75% and 100% of RAP material and two oil-based RAs were investigated in terms of moisture, rutting, fatigue and cracking resistance. It was concluded that the mixtures containing RAP material had high resistance against rutting, moisture damage, and low-temperature cracking. Using RAs had a slight adverse effect on these parameters. On the other hand, fatigue and intermediate-temperature crack resistance of asphalt mixtures were impaired by using RAP material. Recycling agents used in this study could improve fatigue and intermediate-temperature cracking performance of the mixtures depending on the RAP content and testing conditions.