AASHTO PP 75:13(2015) Standard Practice for Vacuum Drying Compacted Asphalt Specimens.
4.1.1. The device shall be capable of controlling the vacuum, airflow, and temperature in order to properly dry the specimen at close to room temperature.
4.1.2. The device shall display a pressure value that indicates a dry point in the chamber and number of cycles.
4.1.3. The device shall have a plate for removing water from the bottom surface of the specimen
4.1.4. The device shall have a means to trap moisture that is removed from the sample.
4.2. A handheld infrared temperature sensor accurate to ±5°C (±9°F) shall be used to measure surface temperature of the specimens.
4.3. Weighing Device—The weighing device shall conform to the General-Purpose Balances and Scales, Class G 2 requirement of M 231.
5.1. Specimens shall be kept and stored at temperatures above 15°C (60°F).
5.2. Plug the unit into a power outlet and turn on the switch.
Note 1—Keeping the unit in the off position when not in use can prolong the operating life of the components used in the vacuum drying device.
5.3. Dry the moisture trap (if necessary) and the specimen (vacuum) chamber. Run the unit without any specimens. The unit should display a pressure value that indicates a known dry point. If the unit fails to achieve a dry point pressure value, as recommended by the manufacturer, check that the lid and all hose connections are well sealed. If needed, refer to the manufacturer’s troubleshooting instructions.
5.4. Measure the sample temperature with a handheld infrared thermometer. Make sure the specimen temperature is above 15°C (60°F).
5.5. Remove any standing water from the surface of the specimen by using a paper towel or an absorptive cloth.
5.6. Place the specimen inside the vacuum chamber.
5.7. Place lids on the vacuum chamber and moisture trap (if applicable). Press “Start” to begin the drying process.
5.8. The machine will automatically stop when the specimen is dry. The unit shall be calibrated at the factory or by the operator to sense a “dry specimen condition.” The pressure is monitored throughout the drying process to ensure “dry specimen condition” pressure is achieved in the unit. Note 2—Sample is considered dry when the measured weight after vacuum drying process is within 0.1 percent or less of 24-h oven drying at 50°C. This check is only recommended when verification of drying pcrformance is needed.AASHTO PP 75 pdf download.