AASHTO R 15-18 (2022)

This standard practice covers the laboratory testing required to evaluate asphalt additives and modifiers in both asphalt binders and mixtures. The terms “additive” and “modifier” are used interchangeably and are broadly interpreted to include any materials added to asphalt binder in minor amounts, other than mineral fillers, sand, and aggregates, whose purported effect is to change the effective performance grade of the asphalt binder, or to otherwise improve the performance and service life of pavements or maintenance materials by improving the properties of the asphalt binder or asphalt mixture, or both. This standard does not include modifications due to the use of recycled materials.

Following is a list of the common purposes for which an additive/modifier may be added:

• Anti-Rutting (permanent deformation)
• Anti-Cracking:
  • Thermal Cracking (low-temperature cracking, thermal-fatigue cracking)
  • Load-Associated Fatigue Cracking
• Anti-Stripping—Moisture susceptibility of the asphalt–aggregate bond
• Warm Mix Asphalt (WMA) Technologies/Compaction Aids
• Extenders/Softeners