Influence of Recycling Agents Addition Methods on Asphalt Mixtures Properties Containing Reclaimed Asphalt Pavement (RAP)

Recycling agents (RAs) are used to restore the physicochemical properties of the aged asphalt binder existing in the reclaimed asphalt pavement (RAP) material. The best location for adding the RAs in the manufacturing process of the asphalt mixtures containing RAP has always been of concern to asphalt mixture researchers. In this study, vegetable, paraffinic and aromatic extract oils were used as RAs. The effect of RA location on the performance properties of the asphalt mixtures containing different percentages of the RAP material was investigated by adding the RAs in three different locations, including in the virgin binder, in the hot RAP material, and in the final mixture. For this aim, the rutting, cracking, and moisture sensitivity of the mixtures containing different RAs at different locations was investigated. The results showed that the best location for adding the RAs is different for various RAs. The best place for adding the paraffinic, aromatic extract, and vegetable oils in terms are in the virgin binder, in the RAP, and the final mixture, respectively. Therefore, using RAs in their appropriate location can improve the mechanical properties of asphalt mixtures containing RAP.