To summarize the status of SMAs around the world in regard to the design of mixtures and their aggregate gradations, two general trends consist of the following:
• German SMAs and others made by those more-or-less faithful to German guidelines have evolved somewhat based on long-standing systematic observations and experiences in SMA technology
• Research and development continues on new ways of designing SMAs; U. S. and Dutch techniques may be representative of that trend (see Chapter 7).
Various mixtures worldwide are referred to as SMA although they may differ greatly from Dr. Zichner’s invention. Some of these variants should, in principle, actually be called something besides SMA. Undoubtedly they are still gap-graded mineral mixes and SMA-like, but they are not identical with Dr. Zichner’s
Splittmastixasphalt.
In subsequent chapters, SMA composition will be discussed according to a scheme drawing on both trends. The existence of so many different attitudes toward the SMA mix has been problematic in selecting the right way to express the variety of opinions in a methodical and comprehensive way. That is why some specific references to particular trends may appear occasionally.
