Evaluation of Stability, Nature of Modifier, and Short-Term Aging of Modified Binders Using New Tests: LAST, PAT, and Modified RTFO

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Abstract
In a recent survey of users and producers of modified asphalts, stability and short-term aging were two of the main concerns regarding the use of modified asphalts. In an NCHRP project, a concentrated effort was put into development of revised or new testing procedures to better characterize the nature of modified asphalt and to solve some of the difficulties with using existing aging procedures developed for neat asphalts and modified asphalts. Three main procedures have been proposed to complement the existing Superpave procedures: the laboratory asphalt stability test, for measuring the storage stability of asphalt binders; the particulate additive test, for separation of particulate additives; and the modified rolling thin film oven test for short-term aging. The background behind the development of these test methods is explained, and typical data collected for a number of modified asphalts are presented. The results indicate that these tests show high promise in covering characteristics not covered by the current Superpave binder specifications and in solving some of the problems with the existing aging methods. The results also indicate that the behavior of modified binder can be very complex and that the method of data interpretation is very critical.