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It happens that, after the completion of an SMA course, a sight reminiscent of mas­tic asphalt may unfold before the observer’s eyes (Figure 11.8). Such a closed SMA structure means utter failure and the likely removal and replacement (possibly by recycling) of the layer. This kind of problem is directly connected to the discussion in […]

Stabilizer lumps occur rarely, but sometimes they bring fairly unpleasant consequences. The problem lies in the fact that symptoms may only be seen some time after the placement of an SMA course. Results such as the following are quite spectacular: • Initial formation of bulging spots in a newly made course • A spot of […]

If porous spots are not visible around the fat spot, this is not a case of classic segrega­tion. We may suppose that the fat spot appeared because of an excess of mastic volume (an error of design). It may also have been caused by too much energy applied during compaction (improperly adjusted or unskillfully applied […]

An area with a definite shortage of mastic adjacent to the fat spot (visibly porous) is a clear sign that this is a case of an SMA segregation—namely, separating the coarse aggregates from the mastic. If the quantities of all the ingredients have been properly selected, the high accumulation of one component in one location […]

Mastic fat spots may be distinguished from binder fat spots using a tool to check the composition of a particular fat spot. All the elements that make mastic—binder, filler, fibers and sand—can usually be identified in a cross section of a fat spot. It is neces­sary to examine what is going on around the fat […]

Longitudinal fat spots are the most frequently seen defects when using SMA. Such spots may be defined as areas with an excess of binder or mastic that are shaped longitudinally and are parallel to the path of the paver. There are two types of longitudinal fat spots—binder fat spots and mastic fat spots—which differ only […]

As with other asphalt mixtures, problems frequently occur with SMA, too. They may develop at the stage of design, production, or application. Some of the troubles described here also appear in asphaltic concrete or other asphalt mixtures, but a dis­tinctive feature of SMA is that its shortcomings are revealed in a particularly clear, and sometimes […]

In regard to edge sealing, the following reasonable solution definitely extends the durability of a pavement and has been adopted in German practice (Milster et al., 2004): • An extra layer of tack coat (of hot binder) is placed on the edges of pavement (between the layers), minimum 10 cm wide. • A binder layer, […]

Grit is spread on an hot SMA mixture using one of the two following techniques: • With a gritter installed on a roller, during the first pass of the roller there is no gritting, but during the second pass the gritting is turned on. One should remember to grit in one direction of roller movement, […]

Grits usually consist of different types of aggregates, such as the following: • Aggregate 2/5 (or 2/4) mm, cleaned and hot, applied at a rate of 1.0-2.0 kg/ m2, for SMA with a gradation of at least 0/11 mm (Figure 10.14) • Aggregate 1/3 mm, washed and hot, applied at a rate of 0.5-1.5 kg/m2, […]