Page 166 - RoadCem Manual - PCT BV

The photograph to the right shows a road surface that consists of a hot rolled asphalt wearing course and 20mm. precoats.
POROUS ASPHALT / PERVIOUS MACADAM
Porous asphalt is the same material that used to be called Pervious Macadam, a material that has been designed to be porous. Do not take another material i.e. stone mastic asphalt and make it porous by "dragging" it with the paver to a layer thickness less than it should be and hence creating voids in the matrix, that is not how a porous surface layer should be achieved.
Open graded macadams will also have a high degree of porosity. These materials should be laid on an impervious basecourse.
Figure 5.62 Pavement structure
It is this open structure that creates the surface texture and allows water to pass thought connecting voids thus reducing splash and spray, at least while the voids remain unclogged. This material, with a stiffer and perhaps modified binder, may be used to provide a free draining and brings on aqoustic isolation "quiet" surface. Porous surface course bituminous mixtures must be laid on a strong smooth and impervious base layer.
Porous asphalt is losing favour as a bituminous surfacing option. Although a material that may cause less surface noise to be generated and reduces spray, there have been problems in laying. Its life is much shorter than a hot rolled asphalt wearing course and there are problems with winter maintenance because porous asphalt needs salting at higher rates than impervious materials, as it is a "colder" surface.
These are just some examples of the surfacing options that one can consider. Each country and region may have other options that can be considered.
5.10 PriorityAssuranceandQualityControl
Quality assurance in road construction includes the total system within the construction site that ensures correct quality of the final road and associated structures. Besides conventional site control, quality assurance also includes the measures that contractors themselves apply for this purpose during operations.
Quality control includes laboratory and field testing of materials and construction. It forms part of the overall quality assurance system. It is applied in various ways, depending on the type of contract.
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