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Throughout this book the term fine aggregate has been conventionally used as a term for the passive aggregate. Its upper limit depends on us—or more specifically, on the type of coarse grain previously in process of SMA design accepted as a skeleton maker. The task of the fine aggregate is to fill voids among the […]

Mastic is the second largest component of stone matrix asphalt (SMA); it is approxi­mately 20-25% by weight of the mixture and 30-35% by volume. About 35-40% (v/v) of the compacted coarse aggregates is made up of voids, and after filling the aggregate with mastic, 3% to 5% (v/v) of empty space will be left. Mastic[9] […]

A downward trend that has been recently evident in Germany involves reducing the aggregate blend gradation discontinuity and establishing an upper limit on the coarse aggregate (bigger than 2 mm) content. These changes have been justified as ways to secure a more durable wearing course and to improve its compaction. Although in some respects very […]

In some countries (e. g., the United States and the Netherlands) a method of con­structing an SMA skeleton has been developed based on the control of stone-to-stone contact or a real gradation discontinuity. Based on these methods, the definition of SMA is expanded to mean an asphalt mixture containing mastic stabilizer (drainage inhibitor) with a […]

to the original german method The original German approach (by Dr. Zichner) to designing SMA aggregate blends is based on having adequate ratios of various aggregate fractions. In that context, the stone-to-stone contact is neither specifically analyzed nor controlled. Since the beginning of the SMA concept, the ratios established by Dr. Zichner have been only […]

Our aim in designing an SMA’s aggregate structure has already been identified—a strong skeleton of coarse grains. Let us now consider what requirements an aggre­gate mix has to meet to create such a desirable skeleton. There is no room in it for too many fine or weak grains. The key solution for that question is […]

What is the reason for developing mixes with stronger mineral skeletons? Surely it is because of heavier and heavier traffic. Not only have axle loads and traffic volumes grown steadily, but the structures of vehicle tires have also changed. The increased popularity of super single tires, for example, has changed the level of stresses applied […]

In this part of the book we shall deal with the grains within the mix structure that are active in forming a coarse aggregate skeleton. The following significant questions will be answered, too: • How is a stone matrix asphalt (SMA) mix skeleton formed? • What does a gap gradation mean? 2.1 DEFINITION OF AN […]

The content of SMA will be divided into the following parts (Figure 1.4): • Coarse aggregate skeleton • Mastic (i. e., binder, filler, fine aggregate, and stabilizer) • Voids in the asphalt mix This division of SMA into parts (with the predominance of the main two—skele­ton and mastic) has been adopted to better explain the […]

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 […]