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The 30-20-10 rule has more or less rigid proportions of gradation (expressed by amounts passing through selected sieves). Zichner proposed the amount of coarse a

According to the rule described in Section 6.2.2, proper stone-to-stone contact is created if the percentage of aggregate passing the 0.075 mm, 2.36 mm, and 4.75 mm sieves equals 10%, 20%, and 30%, respectively. Table 6.11 shows the comparison between the achieved result of Stage 4 and ratios according to the 30-20-10 rule. There are […]

In Chapter 2, Table 2.1 cites the recommended ratios of individual SMA coarse aggregate fractions from the German DAV handbook (Druschner and Schafer, 2000). The comparison of the achieved result from Example II with ratios required in Germany is shown in Table 6.10. The comparison in Table 6.10 shows that our SMA differs both from […]

As a result of the actions undertaken during Stages 1-4, the present mix is distin­guished by a very high proportion of coarse particles (the strong skeleton) and the maximum discontinuity of gradation allowed by the gradation curves of SMA 0/11 according to ZW-SMA-2001. The share of the coarse aggregate fraction was fixed all the time […]

After examining the gradation curve in Figure 6.6, we can conclude that lower­ing the curve on the 8-mm sieve simply means a reduction in passing from 55 to 45%, which is an increase in the quantity of particles bigger than 8 mm from 45 to 55%. This move means that we should increase the content […]

This time, let us add that 20% removed from 2/5.6 mm chippings to 8/11.2 mm chippings (that makes 25% + 20% = 45%), leaving the content of fraction 5.6/8 the same as in Stage I (25%). The composition of the new mix is shown in Table 6.8, while its gradation curve is shown in Figure […]

When designing the shape of a gradation curve in the coarse aggregate fraction (larger than 2 mm), it is worthwhile to pay attention not only to the percentage of grains larger than 2 mm (retained on a 2 mm sieve) but also to the ratios of contents of various coarse aggregate fractions. According to many […]

Designing the coarse aggregate part of an SMA mix differs widely from designing an asphalt concrete (AC) mix. The unexpected difference lies in the various results of similar actions. Let us consider the example of SMA gradation curves. It should be kept in mind that SMA has a strong aggregate skeleton with little to none […]

Let us design the SMA coarse aggregate fraction (particles larger than 2.0 mm). The majority of guidelines recommend its content should be about 70-80% (m/m) of the whole aggregate mix, making it the major component. It may seem that there is little room to maneuver; however, there is a huge potential for controlling the SMA […]

Some hold the opinion that the best gradation curve is the one passing exactly in the middle of the space between the upper and lower gradation limits. To a certain extent in some cases this may be true; however, in the majority of cases it is not. The shape of a design gradation curve exerts […]