Stone matrix asphalt (SMA) mixtures and courses made from them have many strengths. Naturally, these mixtures must be well-designed, but that attribute has various shades of meaning. A review of publications on this subject has not revealed a method that is clearly “the best.” There is as wide a variety of design methods as there are approaches to the roles of particular constituent materials.
Having decided to place such a mixture, a civil engineer faces a challenge. It is not an easy material to deal with, neither during design nor construction. The first essential task is to achieve the proper SMA composition. All the remaining aspects of SMA construction—namely, production, transportation, placement, and compaction—are affected by this first step. Most problems at subsequent stages of work with SMA can be avoided only by achieving a good mix design.
In the various sections of this chapter, the following issues will be presented and discussed:
• Selection criteria for an aggregate mix size (the maximum particle size) depending on the design thickness of the course
• Design method with gradation limits
• Designing the part of the aggregate mix greater than 2 mm
• Designing the part of the aggregate mix less than 2 mm
• Selection of the proper binder content
• Final assessment of the properties of the designed mixture
Chapter 7 presents an overview of selected SMA design methods developed in various countries.
