1、Designation: D 7227 06Standard Practice forRapid Drying of Compacted Asphalt Specimens UsingVacuum Drying Apparatus1This standard is issued under the fixed designation D 7227; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the yea
2、r of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers the process of drying compactedasphalt specimens using vacuum drying apparatus.1.2 The spec
3、imens dried by this practice remain at roomtemperature, which helps in maintaining specimen integrityduring the drying process.1.3 This practice can be used for compacted cylindrical andcubical bituminous laboratory and field specimens1.4 This practice can also be used for drying other construc-tion
4、 materials such as concrete, soils, aggregates and looseasphalt mixtures. Use manufacturers recommendations fordrying other construction materials.1.5 The values stated in SI units are to be regarded as thestandard.1.6 This standard does not purport to address all of thesafety concerns, if any, asso
5、ciated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory requirements prior to use.2. Referenced Documents2.1 ASTM Standards:2D 5361 Practice for Sampling Compacted Bituminous Mix-tu
6、res for Laboratory Testing3. Significance and Use3.1 Specimen dry weight is a critical measure in determi-nation of accurate density and many other tests in the construc-tion and raw materials industries. Drying specimens at roomtemperature is required for some tests and provides an advan-tage for o
7、ther tests to ensure the integrity and to preserve thecharacteristics of specimens.3.2 This practice covers drying compacted asphalt speci-mens in a vacuum chamber that is capable of keeping thespecimen at close to room temperature. A vacuum pumpreduces the pressure inside the chamber, thus allowing
8、 water toevaporate at low temperature. Since the specimen naturallycools during the evaporation process, making water harder toevaporate, it is important to have proper temperature controlsin the chamber to ensure specimen remains at close to roomtemperature. Automatic controls within the unit allow
9、 thespecimen to remain at close to room temperature by periodi-cally allowing a flow of warm air to enter the vacuum chamber.Cycling between vacuum and airflow conditions allows thespecimen to dry in a short period of time. Completely saturatedspecimens with over 30 g of retained water can be dried
10、inabout 30 minutes. For most field cores that are not completelysaturated the drying time is generally less than 15 minutes.NOTE 1Cycle time (period) can depend on the material composition.Each cycle involves an alternating period of 30 to 180 seconds of vacuumoperation and 30 to 120 seconds of air
11、flow.3.3 This method can be used for 100 mm diameter, 150 mmdiameter cylindrical, and cubical compacted bituminous speci-mens.3.4 This method can also be used for drying loose asphaltmixtures, aggregate samples and other solid specimens. Followmanufacturers recommended procedures for drying specimen
12、sother than compacted bituminous specimens.3.5 This method can be used to determine moisture contentand amount of water loss during drying by weighing thesample before and after the drying operations.4. Apparatus4.1 Absorptive cloth or paper towels, for drying water fromsurface of the specimens.4.2
13、Vacuum Chamber, with a pump capable of evacuating asealed and enclosed chamber to a pressure of 6 mm Hg, whenat sea level. The chamber shall be large enough to accommo-date specimens of 150 mm width or diameter and 180 mm inheight. The device shall have an automatic vacuum, airflowand temperature co
14、ntrol features to ensure proper drying of thespecimen at close to room temperatures. Automatic controls of1This practice is under the jurisdiction of ASTM Committee D04 on Road andPaving Materials and is the direct responsibility of Subcommittee D04.21 onSpecific Gravity and Density of Bituminous Mi
15、xtures.Current edition approved Feb. 15, 2006. Published February 2006.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe AST
16、M website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.the unit shall be calibrated by the manufacturer prior to initialuse. The device shall have the capability to display vacuumreadings in the chamber and number of cycles.4.3 Wa
17、ter Removable Plate, used for removing free waterfrom the bottom surface of the specimen chamber.4.4 Electronic cold trap with an airflow divider plate, usedfor trapping water and stopping it from entering the vacuumpump.4.5 A handheld infrared temperature sensor accurate to65C for measuring surface
18、 temperature of the specimens.5. Sampling5.1 Test specimens may be molded from laboratory pre-pared specimens or taken from the pavement in the field. Fieldspecimens should be obtained in accordance with PracticeD 5361.6. Test Specimen6.1 To speed up the drying process, keep and maintain thespecimen
19、s to be dried between 15 C and 30C.6.2 If desired, specimens may be separated from otherpavement layers in accordance with D 5361.7. Procedure7.1 Turn On the Unit:Plug the unit in a power outlet and turn on the on/off switch.Follow manufacturers recommendations for warm up and selftest procedures.7.
20、2 Daily Test: Everyday before starting the testing opera-tion, dry the cold trap and the specimen chamber. Run the unitwithout any specimens. The pressure reading on the displayshould be 6 mm Hg. or less. If the indicated pressure is higherthan 6 mm. Hg, check the system for items that might needser
21、vice, such as oil level and quality, seals, or water in thechamber. Refer to the manufacturers trouble shooting instruc-tions for obtaining a proper pressure reading in the chamber.For drying other construction materials, follow manufactuersrecommendations for pressure requirements in the chamber.7.
22、3 Drying Specimens: Use a handheld infrared thermom-eter to ensure that the surface temperature of the specimen isbetween 15C and 30C. If the specimen is below 15C orabove 30C, place the specimens in a room temperatureenvironment until the surface temperature approaches therequired testing temperatu
23、re of 15C to 30C.7.3.1 Use paper towel or an absorptive cloth to remove anystanding water from the surface of the specimen.7.3.2 Place the specimen on top of the specimen supportplate inside the chamber.FIG. 1 Water Removal Plate and Sample Holder Installed in Sample ChamberD72270627.3.3 Place the l
24、id on the vacuum chamber and press the liddown to ensure secure contact between the lid and the chamber.Press the appropriate key, for example the Start key, to beginthe drying process.7.3.4 When the specimen is dry, the unit will automaticallystop. The unit is calibrated at the factory to sense a “
25、dryspecimen condition”. Dry specimen condition is determined atthe factory for the pressure at which no water remains in thechamber. During testing, the unit continuously reads thepressure inside the chamber and checks this pressure againstthe “dry specimen condition” pressure determined duringfacto
26、ry calibration. Follow manufacturers procedure for cali-brating the device to dry specimen condition.NOTE 2Sample is considered dry when the measured weight aftervacuum drying process is 0.2 grams or less of 24-hour oven drying at50C.7.4 Electronic Cold Trap: Liquid and ice, or both, willaccumulate
27、in the cold trap as specimens are drying. Betweendrying specimens and for faster drying, it is best to remove thecold trap lid and the airflow divider plate and wipe out any freestanding water in the cold trap. Always place the divider backinto the cold trap before drying the next specimen.8. Report
28、8.1 Report the following information:8.1.1 At the end of the drying process, report the endingpressure in mm Hg, to the nearest 0.1 mm Hg, and total numberof cycles displayed on the screen. This information may beused by the manufacturer or the user for trouble shooting thedevice, if needed.ASTM Int
29、ernational takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirel
30、y their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand sh
31、ould be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on St
32、andards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).D7227063
