Document ID: chunk:federal_register_of_legislation:F2021C00509:front:0:p31
Version: federal_register_of_legislation:F2021C00509
Segment Type: other
Provision Reference: 
Character Range: 90809–93605

d = square mesh sieve size, in mm
                     dmax = 8 mm for the mean curve
                     dmax = 10 mm for the lower tolerance curve
                     dmax = 6.3 mm for the upper tolerance curve

Figure 2.
           Grading curve of the aggregate in the asphaltic mix with tolerances

           In addition to the above, the following recommendations are given:
             (a) The sand fraction (0.063 mm < square mesh sieve size < 2 mm) shall include no more than 55% natural sand and at least 45% crushed sand;
             (b) The base and sub-base shall ensure a good stability and evenness, according to best road construction practice;
             (c) The chippings shall be crushed (100% crushed faces) and of a material with a high resistance to crushing;
           (d) The chippings used in the mix shall be washed;
           (e) No extra chippings shall be added onto the surface.
             (f) The binder hardness expressed as PEN value shall be 40-60, 60-80 or even 80-100 depending on the climatic conditions of the country. The rule is that as hard a binder as possible shall be used, provided this is consistent with common practice;
             (g) The temperature of the mix before rolling shall be chosen so as to achieve by subsequent rolling the required voids content. In order to increase the probability of satisfying the specifications of paragraphs 2.1 to 2.4 above, the compactness shall be studied not only by an appropriate choice of mixing temperature, but also by an appropriate number of passings and by the choice of compacting vehicle.

           Table 1. Design guidelines

4. Test method

4.1. Measurement of the residual voids content

           For the purpose of this measurement, cores have to be taken fromthe track in at least four different positions which are equally distributed in the test area between lines AA and BB (see Figure 1). In order to avoid inhomogeneity and unevenness in the wheel tracks, cores should not be taken in wheel tracks themselves, but close to them. Two cores (minimum) should be taken close to the wheel tracks and one core (minimum) should be taken approximately midway between the wheel tracks and each microphone location.
           If there is a suspicion that the condition of homogeneity is not met (see paragraph 2.4), cores shall be taken from more locations within the test area. The residual voids content has to be determined for each core, then the average value from all cores shall be calculated and compared with the requirement of paragraph 2.1. In addition, no single core shall have a voids value which is higher than 10%. The test surface constructor is reminded of the problem which may arise when the test area is heated by pipes or electrical wires and cores must