Constituent materials, design, production, and placement of a stone matrix asphalt (SMA) mixture were discussed in previous chapters. It would not make sense to spend this much time discussing the mix if SMA courses had not been characterized with many strong points. Conversely, it should be openly admitted that it is not a perfect mixture, and it also has a couple of run-of-the-mill or slightly poorer properties among some very remarkable and even outstanding ones. In any case, its lack of perfection does not affect the final appraisal of SMA as a very useful material for pavements. After all, the rapid increase in SMA applications all over the world has not been exclusively brought about by fashion.
Next, the following operation and maintenance properties of SMA courses will be elaborated on
• Resistance to permanent deformation
• Crack resistance
• Fatigue limit
• Antinoise properties
• Antispray and antiglare properties
• Antiskid properties
• Durability
• Permeability
• Impact on fuel consumption while driving
• Economic effectiveness
This discussion will begin with a short comparison of SMA and other competitive mixtures that are used for wearing courses. Table 12.1 shows a comparison of selected properties of SMA, open graded asphalt, ultra-thin friction courses, and continuous graded asphalt mixtures (Pretorius et al., 2004). One can see from this table that SMA mixtures generally compare very favorably with the other types of mixtures but that SMA may not be the best choice for all applications.
