AASHTO T 331:2021 Standard Method of Test for Bulk Specific Gravity (Gmb) and Density of Compacted Asphalt Mixtures Using Automatic Vacuum Sealing Method

AASHTO T 331:2021 Standard Method of Test for Bulk Specific Gravity (Gmb) and Density of Compacted Asphalt Mixtures Using Automatic Vacuum Sealing Method.
APPARATUS
Bag Cutter—A knife, scissors, or other types of clipping devices may be used to quickly open bags.
5.2. Oven—The oven shall be capable of maintaining the appropriate temperature for drying specimens to a constant mass.
5.3. Weighing Device—The weighing device shall have sufficient capacity, be readable to 0.1 percent of the sample mass or better, and conform to the requirements of M 23 1. The weighing device shall be equipped with a suitable suspension apparatus and holder to determine the mass of the specimen while suspended from the center of the scale pan of the weighing device.
5.4. Plastic Bags—The two most commonly used sizes of bags are designated as small and large size bags. The small bags shall have a minimum opening of 235 mm (9.25 in.) and a maximum opening of 260 mm (10.25 in.) with a mass of less than 35 g. The large bags shall have a minimum opening of 375 mm (14.75 in.) and a maximum opening of 394 mm (15.5 in.) with a mass of 35 g or more. The bags shall be made of a plastic material that will not adhere to asphalt film and shall be puncture-resistant, capable of withstanding sample temperatures of up to 70°C (158°F), impermeable to water, and contain no air channels for evacuation of air from the bag. The bags shall have a minimum thickness of 0.100mm (0.004 in.) and a maximum thickness of 0.152 mm (0.006 in.). The manufacturer shall provide the bag correction factor (apparent specific gravity) of the bags (usually located in the operator’s manual). See the manufacturer’s recommendations to ensure proper handling of bags.
5.5. Specimen Sliding Plates—Level and smooth-sided planar filler plates shall be inserted into the chamber to keep the samples of various heights level with the seal bar while being sealed. The plates shall be removable and of the appropriate dimensions to easily fit into the vacuum chamber. A smooth-sided specimen supporting plate shall easily slide on top of the smooth-sided plates. The opposite side of the smooth-sided specimen supporting plate shall have a cushioning membrane to help prevent tears in the plastic bag. The plate shall be large enough to fully support the specimen but small enough to allow movement during the sealing process.
5.6. Suspension Apparatus—The wire suspending the container shall be of the smallest practical size to minimize any possible efficts of a variable immersed length. The suspension apparatus shall be constructed to enable the container to be immersed to a depth sufficient to cover it and the test sample during weighing.
5.7. Thermometer—ASTM 17C (17F) as provided in ASTM El, having a range of 19 to 27°C (66 to 80°F), graduated and conforming to ASTM E1. An electronic temperature measuring device, such as a resistance thermometer or thermocouple. may be used.AASHTO T 331 pdf download.