Standard Practice for Rapid Drying of Compacted Asphalt Mixture Specimens Using Vacuum Drying Apparatus
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.
FIG. 1 Water Removal Plate and Sample Holder Installed in Sample Chamber
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 air 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 air flow.
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.
1.1 This practice covers the process of drying compacted asphalt mixture specimens using vacuum drying apparatus.
1.2 The specimens dried by this practice remain at room temperature, which helps in maintaining specimen integrity during the drying process.
1.3 This practice can be used for compacted cylindrical and cubical laboratory and field asphalt mixture specimens.
1.4 This practice can also be used for drying other construction materials such as concrete, soils, aggregates, and loose asphalt mixtures. Use the manufacturer’s recommendations for drying other construction materials.
1.5 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalent; therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with the standard.
1.6 The text of this standard references notes and footnotes which provide explanatory material. These notes and footnotes (excluding those in tables and figures) shall not be considered as requirements of the standard.
1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory requirements prior to use.
1.8 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
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