The requirements for SMA binders used in the United States are related to the Superpave system prevailing in the country. The basis for the selection of binders for wearing courses, in principle their functional type (performance grade [PG]), is the climate of the given area of application. So all binders have to meet the same requirements for deformation resistance, fatigue, and low temperature cracking, but they meet those limits at different temperatures that relate to the climate in various parts of the United States. In specified situations, such as low-speed traffic or very high-traffic loads, the system additionally allows increasing the upper (high temperature) grade of the binder. Finally, a binder that meets the specific climatic and traffic requirements for the construction location is then specified or selected.
So there are no special nationwide requirements for SMA binders. The rules for binder selection from Superpave are generally followed for all mixtures. Readers interested in the PG system can find detailed information in SHRP or Asphalt Institute publications (e. g., SP-1 Superpave Performance Graded Asphalt Binder Specifications and Testing).
