Document ID: chunk:federal_register_of_legislation:F2021C00509:reg:6:p4
Version: federal_register_of_legislation:F2021C00509
Segment Type: reg
Provision Reference: reg 6 (pt 4/10)
Character Range: 208109–211365

curve

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

          In addition to the above, the following recommendations are given:
          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;
          The base and sub-base shall ensure a good stability and evenness, according to best road construction practice;
          The chippings shall be crushed (100% crushed faces) and of a material with a high resistance to crushing;
          The chippings used in the mix shall be washed;
          No extra chippings shall be added onto the surface;
          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;
          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 l: Design guidelines

                                               Target values
                                                                       Tolerances
By total mass                                  By mass of the
of mix                                         aggregate
Mass of stones, square mesh sieve (SM) > 2 mm  47.6%                   50.5%       +/-5
Mass of sand 0.063 < SM < 2 mm                 38.0%                   40.2%       +/-5
Mass of filler SM < 0.063 mm                   8.8%                    9.3%        +/-2
Mass of binder (bitumen)                       5.8%                    N.A.        +/-0.5
Max. chipping size                             8 mm                    6.3 - 10
Binder hardness                                (see para. 3.2.2. (f))
Polished stone value (PSV)                     > 50
Compactness, relative to Marshall compactness  98%

  4.                                               Test method

  4.1.                                         Measurement of the residual voids content

          For the purpose of this measurement, cores have to be taken from the 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 para. 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