Standard Practice for Rapid Drying of Compacted Asphalt Mixture Specimens Using Vacuum Drying Apparatus

Importancia y uso:

4.1 Specimen dry weight is a critical measure in determination of accurate density and many other tests in the construction and raw materials industries. Drying specimens at room temperature is required for some tests and provides an advantage for other tests to ensure the integrity and to preserve the characteristics of specimens.

4.2 This practice covers drying compacted asphalt mixture specimens in a vacuum chamber that is capable of keeping the specimen at close to room temperature. A vacuum pump reduces the pressure inside the chamber, thus allowing water to evaporate at low temperature. Since the specimen naturally cools during the evaporation process, making water harder to evaporate, it is important to have proper temperature controls in the chamber to ensure the specimen remains at close to room temperature. Automatic controls within the unit allow the specimen to remain at close to room temperature by periodically allowing a flow of warm and dry air, typically generated by an inline air heater, to enter the vacuum chamber. Cycling between vacuum and airflow conditions allows the specimen to dry in a short period of time. Completely saturated specimens with over 30 g [0.07 lb] of retained water can be dried in about 30 min. For most field cores that are not completely saturated, the drying time is generally less than 15 min.

Note 1: Cycle time (period) can depend on the material composition. Each cycle involves an alternating period of 30 to 180 s of vacuum operation and 30 to 120 s of airflow.

4.3 This method can be used for 100 mm [4 in.] diameter, 150 mm [6 in.] diameter cylindrical, and cubical compacted asphalt mixture specimens.

4.4 This method can also be used for drying loose asphalt mixtures, aggregate samples, and other solid specimens. Follow the manufacturer’s recommended procedures for drying specimens other than compacted asphalt mixture specimens.

4.5 This method can be used to determine moisture content and amount of water loss during drying by weighing the sample before and after the drying operations.

Note 2: The quality of the results produced by this standard are dependent on the competence of the personnel performing the procedure and the capability, calibration, and maintenance of the equipment used. Agencies that meet the criteria of Specification D3666 are generally considered capable of competent and objective testing, sampling, inspection, etc. Users of this standard are cautioned that compliance with Specification D3666 alone does not completely ensure reliable results. Reliable results depend on many factors; following the suggestions of Specification D3666 or some similar acceptable guideline provides a means of evaluating and controlling some of those factors.

Subcomité:

D04.21

Referida por:

D7063_D7063M-18, D1188_D1188M-22, D2726_D2726M-21, D6752_D6752M-23, D2726_D2726M-21

Volúmen:

04.03

Número ICS:

91.100.50 (Binders. Sealing materials)