AASHTO R 15-18涵盖了评估纯沥青和沥青集料热混合料中沥青添加剂和改性剂所需的实验室测试。术语“添加剂”和“改性剂”可互换使用，广义上解释为包括少量添加到沥青粘合剂中的任何材料，矿物填料、砂和骨料除外，其目的是通过改善沥青粘合剂或热拌沥青或两者的性能来改善路面或维护材料的性能和使用寿命。

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 CrackingAnti-Stripping—Moisture susceptibility of the asphalt–aggregate bondWarm Mix Asphalt (WMA) Technologies/Compaction AidsExtenders/Softeners