Effects of recycling agents on aged asphalt binders and reclaimed asphalt concrete

This paper aims to study the effect of adding different ratios (from 10 to 40%) of three recycling agents (RAs), including RA-25, RA-75 and RA-250, to the reclaimed asphalt binder (RAB) with a viscosity of 42800 poises and also to the reclaimed asphalt concrete (RAC) according to the Marshall mix design method. The study includes a variety of tests designed to determine the difference between the three RAs in terms of penetration, viscosity, softening point, ductility, toughness of the asphalt binder, as well as indirect tensile strength, and stability value of Marshall specimens. The results show that adding the RA increased the cohesiveness of RAB and thus improved the applicability of RAB. Of the three RAs in this study, RA-25 offered the best performance when added to asphalt binder. This study proposes a recycling model to predict the changes in RAB viscosity when adding RAs. The results of this model show a close fit with experimental data from laboratory tests. This model allows highway engineers to estimate the amount of RA added to aged binder. Marshall tests show that the RA-75 specimen had higher indirect tensile strength and stability value than the RA-25 and RA-250 specimens. Based on overall performance and cost comparisons among the three RAs, this study regards RA-75 as the RA of choice.