AASHTO R 15

Description / Abstract: This standard practice covers the laboratory testing required to evaluate asphalt additives and modifiers in both neat asphalt and in asphalt–aggregate hot 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 improve the performance and service life of pavements or maintenance materials by improving the properties of the asphalt binder or hot mix asphalt, or both.

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.

Antioxidants.

Recycling (not included).

Recycling is omitted from this standard practice. It is felt that consideration of the various characteristics of the material from the pavement to be recycled and formulation of the recycle mix are so involved as to make inclusion of recycling in this standard practice cumbersome and impractical.

The values stated in SI units are to be regarded as the standard.