Document ID: chunk:federal_register_of_legislation:F2021C00509:front:0:p47
Version: federal_register_of_legislation:F2021C00509
Segment Type: other
Provision Reference: 
Character Range: 136241–139165

voids content

           The residual voids content, Vc, of the test track paving mixture shall not exceed 8 per cent. For the measurement procedure, see paragraph 4.1.

2.2. Sound absorption coefficient

           If the surface fails to conform to the residual voids content requirement, the surface is acceptable only if its sound absorption coefficient, alpha, < 0.10. For the measurement procedure, see paragraph 4.2. The requirement of paragraphs 2.1. and 2.2. is met also if only sound absorption has been measured and found to be alpha < 0.10.

           Note: The most relevant characteristic is the sound absorption, although the residual voids content is more familiar among road constructors. However, sound absorption needs to be measured only if the surface fails to conform to the voids requirement. This is because the latter is connected with relatively large uncertainties in terms of both measurements and relevance and some surfaces may therefore be rejected erroneously when the voids measurement only is used as a basis.

           2.3. Texture depth

           The texture depth (TD) measured according to the volumetric method (see para. 4.3. below) shall be:
                           TD > 0.4 mm

2.4. Homogeneity of the surface

           Every practical effort shall be taken to ensure that the surface is made to be as homogeneous as possible within the test area. This includes the texture and voids content, but it should also be observed that if the rolling process results in more effective rolling at some places than others, the texture may be different and unevenness causing bumps may also occur.

2.5. Period of testing

           In order to check whether the surface continues to conform to the texture and voids content or sound absorption requirements stipulated in this standard, periodic testing of

           the surface shall be done at the following intervals:
             (a)   For residual voids content or sound absorption:
             when the surface is new;
             if the surface meets the requirements when new, no further periodical testing is required. If it does not meet the requirement when it is new, it may do later because surfaces tend to become clogged and compacted with time.
             (b)   For texture depth (TD):
             when the surface is new;
             when the noise testing starts (NB: not before four weeks after laying);
             then every 12 months.

3. Test surface design

           3.1. Area

           When designing the test track layout it is important to ensure that, as a minimum requirement, the area traversed by the vehicles running through the test strip is covered with the specified test material with suitable margins for safe and practical driving. This will require that the width of the track is at least 3 m and the length of the track extends beyond lines AA and BB by at least 10 m at either