The Use and Performance of Asphalt Binder Modified with Polyphosphoric Acid (PPA)

Background The modification of asphalt binder to improve performance properties has grown significantly since the implementation of the Strategic Highway Research Program (SHRP) binder specifications. There has been increased use of polymers, crumb rubber modifier and Polyphosphoric Acid (PPA). There has been concern by many highway agencies about the performance characteristics of PPA modification and possible negative interactions with other mix components such as lime and liquid anti-strips. There have been anecdotal stories about both failures and successes. The Federal Highway Administration in cooperation with the Transportation Research Board and Minnesota DOT sponsored a workshop as an attempt to bring together the real facts about PPA modified asphalt and performance. Researchers and practitioners with real knowledge and experience presented the latest information on the PPA modification and performance characteristics. The workshop agenda was developed to promote interactive discussion between presenters and participants.