The principles of designing an aggregate mix and then the content of binder are presented in Figure 7.12. It is an illustration of a telescopic[37] method of creating SMA, which involves inserting consecutive elements into free space (air voids) in a compacted component of a larger size. In other words:
• A volume of fine aggregate is inserted into the air voids in the compacted coarse aggregate skeleton with the effect of increasing the air voids among the coarse aggregates (enlarging effect).
• A volume of filler particles is inserted into the air voids in the compacted fine aggregate.
• A volume of binder is introduced into the air voids in the compacted filler.
• The free space remaining after inserting all these elements produces the content of air voids in a compacted SMA.
Voids Enlarging effect
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Filler |
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Binder + stabilizer |
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FIGURE 7.12 Placing consecutive elements of SMA in a mixture. (From Voskuilen, Ideas for a volumetric mix design method for Stone Mastic Asphalt. Proceedings of the 6th International Conference Durable and Safe Road Pavements, Kielce [Poland], 2000. With permission.) |
Filling the air voids with the subsequent elements has already been partially demonstrated and discussed when explaining the concept of air voids in a filler (see Chapter 3).
Determining the density of all the SMA components is the basis of the design activity because the Dutch method is a volumetric-type method.
