SMA surface seepage is directly related to excessive porosity of a compacted mixture (see Chapter 12) and the condition (watertightness) of the course situated just under the SMA. When assessing the watertightness of an SMA course, one must not forget that water permeability is determined not only by the contents of voids on the surface of a compacted course but also by the shape and interconnectedness of the inner pores. Finally, most national regulations and numerous publications recommend a [68]
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FIGURE 11.10 The surface of an SMA course just after spreading at too low a temperature. (Photo courtesy of Krzysztof Blazejowski.) |
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FIGURE 11.11 Seepage of water through an SMA layer. (Photo courtesy of Bohdan Dolzycki.) |
limit of 6.0% (v/v) air voids in a compacted course, above which a course becomes partially permeable to water.
A tight intermediate course under the SMA, which prevents the penetration of water and water vapor deep into the pavement, is conducive to the development of SMA surface seepage (Figure 11.11).
