# Recycling Aged Asphalt Using Hard Asphalt Binder for Hot-Mixing Recycled Asphalt Mixture
###### Abstract  
Increasing the content of reclaimed asphalt pavement material (RAP) in hot-mix recycled asphalt mixture (RHMA) with a satisfactory performance has been a hot topic in recent years. In this study, the performances of Trinidad lake asphalt (TLA), virgin asphalt binder, and aged asphalt binder were first compared, and then the modification mechanism of TLA on virgin asphalt and aged asphalt was explored. Furthermore, the RHMA was designed in accordance with the French norm NF P 98-140 containing 50% and 100% RAP, and their high-temperature stability, low-temperature cracking resistance, and fatigue performances were tested to be compared with the conventional dense gradation AC-20 asphalt mixture. The results show that the addition of TLA changes the component proportion of virgin asphalt binder, but no new functional groups are produced. The hard asphalt binder modified by TLA has a better rutting resistance, while the fatigue and cracking resistance is lower, compared to both aged and virgin asphalt. The high-modulus design concept of RHMA is a promising way to increase the RAP content in RHMA with acceptable performance. Generally, the RHMA with 50% RAP has similar properties to AC-20. And, when the RAP content reaches 100%, the high- and low-temperature performance and anti-fatigue performance of RHMA are better than AC-20 mixture. Thus, recycling aged asphalt using hard asphalt binder for hot-mixing recycled asphalt mixture to increase the RAP content is feasible. T 2021 17 June 2021 19  
properties after volatilization and oxidation in the field [12]. To this end, the most widely and traditional solution is adding rejuvenators or using soft asphalt binder as the modifier to recover the performance of aged asphalt binder [13; 14]. This solution was shown to be effective in previous publications and engineering projects. However, when RAP content reaches a high percentage (for example, over 50% by the weight of RHMA), the extra softening additives could reduce the rutting resistance of RHMA [15; 16]. Thus, the use of a high percentage of RAP in RHMA has not been properly addressed in current recycling technology. To overcome the negative effect of softening additives on RHMA, previous studies reported that the high-modulus asphalt concrete (HMAC) that originated in France in the early 1980s could be a potential solution [17]. The basic design concept of high-modulus asphalt mixtures is that through the use of hard-grade asphalt binder (with a penetration of about 10-20), fine aggregate gradation, high asphalt binder content (about 6%), and low porosity (generally 3%), the high-modulus asphalt mixture is obtained through the high modulus properties of the hard-grade asphalt binder itself [18]. For example, [PERSON] et al. indicated that the HMAC has a higher binder/aggregate ratio, lower void content, and finer aggregate gradation compared to the conventional dense asphalt concrete [19]. The results show that the addition of RAP can be incorporated into HMAC at relatively higher contents, due to the similar stiffness between the aged asphalt binder in RAP and the high-modulus asphalt binder. To achieve good rutting resistance, hard asphalt binder is a suitable modifier of HMAC. In most cases, the hard asphalt is produced in refineries, and it also can be obtained by blending the virgin asphalt and natural asphaltite, for example, Trinidad lake or Gilsonite-like materials, whose penetration is in range of 8-28 (0.1 mm) [20]. Thus, the design concept of HMAC has the potential of incorporating more RAP contents in the asphalt mixture. However, using hard asphalt binder as the rejuvenator to recover the aged binder is rarely reported in previous studies. The traditional asphalt mixture regeneration technology is to add rejuvenator or soft asphalt to reduce the viscosity of the aged asphalt, thereby restoring its performance. Therefore, this topic may go against the concept of the traditional solutions. The objectives of this work can be summarized as follows.