This study was to perform the viscosity test of adding different ratios (from 10% to 40%) of three recycling agents (RAs), namely RA25, RA75 and RA250, to the reclaimed asphalt binder (RAB) containing a viscosity of 42800 poises. The purpose of the study was to determine the effects of various RAs on the viscosity of aged asphalt binders. The viscosity values were also estimated based on the recycling model of aged asphalt binder developed by authors and the equations developed by Arrhenius (1887), Grunberg and Nissan (1949) and Epps et al. (1980). The results show that there are significant variations in the viscosity of recycling asphalt binder when being added different ratios of RA. The estimated viscosity values computed by the recycling model of aged asphalt binder are closer to the tested results when compared with the equations developed by Arrhenius (1887), Grunberg and Nissan (1949) and Epps et al. (1980). Furthermore, the Recycling Index (RI) developed by the recycling model of aged asphalt binder can clearly and precisely reveal the recycling performance of different kinds of RAs. The Gmix from the equation developed by Grunberg and Nissan (1949) has an apparent effect on estimating the viscosity when adding RA to the RAB.
