AASHTO R 68-15 pdf free download
AASHTO R 68-15 pdf free download.Preparation of Asphalt Mixtures by Means of the Marshall Apparatus.
3.3. ‘ompaction 1—laminer:
3.3.1. Manual Hammer—The compaction hammer (Figure 2) shall have a flat, 98.4 ± 3.2 mm (37/s ± ‘/8 in.) circular tamping face and a 4536 ± 9 g (10 ± 0.02 ib) sliding weight (including a safety finger guard if so equipped) with a free fall of 457.2 ± 1.524mm (18 ± 0.06 in.).
3.3.2. Automatic Hammer—An automatic hammer shall meet the requirements listed for manual hammers in Section 3.3.1. The automatic hammer consists of the mechanical compactor, an automatic counter, and a tapered-foot hammer assembly for rotating-mold models or a flat-foot hammer assembly for stationary mold models. To calibrate the automatic hammer to the manual hammer, compact six specimens: three specimens using the manual hammer and three specimens using the automatic hammer. Use the same number of blows for each specimen. After the specimens have cooled to room temperature, use T 166, T 275, or T 331 to determine the average bulk densities of the two sets of specimens. If the bulk densities of the two sets of specimens are within 2.0 percent of each other, then the results are comparable. If the results are not within 2.0 percent of each other, then the tests need to be repeated using more or fewer blows on the automatic hammer to achieve a comparable density.
3.5. Specimen Mold Holder—Mounted on the compaction pedestal so as to center the compaction mold over the center of the post. It shall hold the compaction mold, collar, and base plate securely in position during compaction of the specimen.
3.6. Ovens or Hot Plates—Ovens or hot plates shall be provided for heating aggregates, asphalt material, specimen molds, compaction hammers, and other equipment to the required mixing and molding temperatures. It is recommended that the heating units be thermostatically controlled so as to maintain the required temperature within 2.8°C (5°F). Suitable shields, baffle plates, or sand baths shall be used on the surfaces of the hot plates to minimize localized overheating.
3.7. Heating Device—A small hot plate with continuously variable heating rate, a sand bath, infrared lamp, or other suitable device shall be available for supplying sufficient heat under the mixing bowl to maintain the aggregate and asphalt material at the desired temperature during mixing. If a hot plate is used, a wire mesh or similar material shall be placed on the hot plate to prevent direct contact between the hot plate and mixing bowl.
3.8. Mixing Apparatus—Mechanical mixing is recommended. Any type of mechanical mixer may be used provided it can be maintained at the required mixing temperature and will produce a well- coated, homogeneous mixture of the required amount in the allowable time, and further provided that essentially all of the batch can be recovered. A metal pan or bowl of sufficient capacity and hand mixing may also be used.
3.9. Air Bath—The air bath for asphalt cutback mixtures shall be thermostatically controlled and shall maintain the air temperature at 25 ± 1°C (77° ± 2°F).
3.10. Ther,nometers—For determining temperatures of aggregates, asphalt binder, and asphalt mixtures. Armored-glass, dial type, or digital thermometers with metal stems are recommended. A range from 9.9 to 204°C (50 to 400°F) with sensitivity of 2.8°C (5°F) is required.
3.11. Balance—A balance meeting the requirements of M 231, Class G 2, for determining the mass of aggregates, binder and asphalt mixture.
3.12. Miscellaneous Equipment—Flat-bottom metal pans or other suitable containers for heating aggregates, containers (gill-type, beakers, pouring pots, or saucepan) for heating asphalt, flat bottom scoop for batching aggregates, steel trowel (garden type) or spatula for spading and hand mixing, gloves for handling hot equipment, paper disks, marking crayons for identifying specimens, and a large spoon for placing mixture in specimen molds.AASHTO R 68-15 pdf download.
