Why and How of Polyphosphoric Acid Modification – An Industry Perspective

Evolution of asphalt binder specifications continually challenges asphalt practioners to seek tools allowing production of binders from most readily available materials. These tools, must facilitate production of asphalt binders which not only meet existing specifications, but ensure long term performance; polyphosphoric (PPA) acid is just one such tool. PPA modification of asphalt is not a new concept as asphalt binders have been chemically modified with PPA to improve high temperature rheological properties without adversely affecting low temperature rheological properties since the early 1970’s. More recently, PPA has been used in SuperPave™ performance-grade (PG) binders to extend the range between the high and low temperature performance. PPA use has increased, as it is being used not only to produce non-polymer modified binders but is used in polymer modified binders as well. While use of PPA in non-polymer modified asphalt binders has a thirty plus year performance history, experienced asphalt practitioners have found that addition of small amounts of PPA to polymer modified binders brings benefits in both handling and performance. Used in conjunction with polymers PPA enables suppliers to achieve PG grades that can be handled, mixed and compacted at reasonable temperatures. Both non-polymer modified and polymer modified plus PPA modified binders have shown improved rutting resistance by addition of PPA. Though successful PPA modification of asphalt binders has a long track record, its use is often debated, sometimes to the point PPA modified asphalt binders have been banned. Opinion has it that such actions result from misinformation as well as lack of understanding of the benefits of PPA as an available tool to improve the performance of asphalt binders. While PPA is banned in some states, others continue its use without issue. This paper discusses common asphalt binder specifications, the relationship of asphalt binder chemical composition to performance grade (PG) properties of asphalt binders, necessary use of PPA modification to meet specifications, the relationship of asphalt composition to PPA loadings necessary to achieve desired properties, expected PG enhancements of PPA modified asphalt binders, and effects of using PPA in non-polymer and polymer modified asphalt binders to meet current PG specifications.

Language

  • English

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Filing Info

  • Accession Number: 01328039
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Jan 20 2011 11:22AM