Compositional evaluation of asphalt binder recycling agents

The results presented here indicate that it is possible to produce a high q uality binder from hardened recycled asphalt by blending with recycling age nts. The properties are presented in terms of Superpave grade and the harde ning susceptibility (HS) which is defined as the slope of log viscosity ver sus infrared measured carbonyl area. First it is shown that the effect of blending aged binder with aromatic age nts is to decrease the HS in rough proportion to the amount of aromatic add ed and this is only slightly dependent on the aromatic source. The presence of saturates in the agent increases the HS. Using an AC-10 asphalt as the softening agent produced much higher HS values. Adding increasing amounts o f aromatic agents on the other hand worsens the Superpave performance grade span. The addition of saturates to the agents has little effect on the spa n but shifts the span to lower temperature. Though increasing amounts of ar omatic agents tended to decrease the grade span, in most instances the span was equal to that produced by blending the aged binder with the AC-10. The hardening susceptibility of the aromatic blends was better than that of th e AC-10 blends and better even than the original asphalt.