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Volumetric properties are among the most frequently cited requirements for SMA mixtures checked at the laboratory level. The primary requirement is to ensure the needed content of voids in compacted samples. Mechanical requirements (e. g., stability) are seldom determined, whereas performance-related properties (e. g., resistance to rutting) can be more often seen in specifications. Table […]

Selecting the binder content in a design SMA mixture is relatively easy. With a cor­rectly designed aggregate mix, it is enough to remember an appropriate content of voids in compacted samples. A thorough understanding of that subject will surely be made much easier by reading Chapter 7, including the description of both the U. S. […]

In the majority of worldwide regulations for SMA, the content of particles passing through the smallest sieve (0.075 or 0.063 mm ) generally ranges between 8% to 13% (m/m). However, adopting extreme quantities may be a risky business—that is, 8% can lead to building too little mastic. On the other hand, a large quantity of […]

In classic SMA composition and in regulations introduced all over the world, the total content of grains smaller than 2 mm has generally been in the range of 15-30% (m/m). When we add the typical filler content (8-13%), we receive up to 22% from the sand fraction (0.063/2.0 mm). But when designing the content of […]

When designing the gradation of aggregate smaller than 2 mm (filler and fine aggre­gate), it should be kept in mind that the excellent properties that allow SMA to resist permanent deformation are connected mainly with a coarse aggregate skeleton. Mastic made of filler, fine aggregate, and binder should play the role of bonding and sealing […]

The relationship between the contents of air voids and coarse grains is well-illus­trated by the laboratory example described next. Two mixes, identified by letters E and F, were produced in laboratory conditions to demonstrate the differences between SMA mixtures with the following different gradations: • Mix E is characterized by a lesser discontinuity (more uniformity) […]

The appearance of significant differences in density among individual fractions of the aggregate mix compels us to discuss volume relations in the aggregate mix and necessary adjustments to the binder content Substantial differences in the densities of aggregates combined in an SMA can cause numerous problems. This situation happens rather seldom; however, it is pos­sible […]

The shape of the aggregate particles, from flat and elongated to cubical ones, exer­cises a certain influence on the SMA mixture. A high content of flat and elongated particles has the following effects: • Increases the content of air voids in a compacted mixture of coarse (active) aggregates • Decreases the workability of a mixture […]

A fixed coarse aggregate content was assumed in Part II of the design example. We explored the subdividing of the coarse aggregate fraction and its subsequent conse­quences. We saw that the shape of the gradation curve in the area larger than 2 mm has great significance on the properties of an SMA mixture. Thus, by […]

Investigations carried out in the Netherlands (Voskuilen, 2000) have proved that the gradation within the coarse aggregate fraction exerts an impact on the distri­bution of voids in a mix. Briefly, the conclusions drawn in the Netherlands are as follows: [25] 6.3.2.2.3 Determining the Size of Active Particles After exercises in changing ratios within the coarse […]