1、Designation: D7227/D7227M 11Standard Practice forRapid Drying of Compacted Asphalt Specimens UsingVacuum Drying Apparatus1This standard is issued under the fixed designation D7227/D7227M; the number immediately following the designation indicates theyear of original adoption or, in the case of revis
2、ion, the year of last revision. A number in parentheses indicates the year of lastreapproval. A superscript epsilon () 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
3、.2 The specimens 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 co
4、nstruc-tion materials such as concrete, soils, aggregates and looseasphalt mixtures. Use manufacturers recommendations fordrying other construction materials.1.5 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard. The values stated ineach system may not
5、 be exact equivalent; therefore, eachsystem shall be used independently of the other. Combiningvalues from the two systems may result in non-conformancewith the standard.1.6 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility
6、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:2D5361 Practice for Sampling Compacted Bituminous Mix-tures for Laboratory Testing3. Significance and
7、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 other tests to ensure the integrity and to pres
8、erve 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 water toevaporate at low temperature. Since t
9、he 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 thespecimen to remain at close to room temper
10、ature 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 0.07 lb of retained water can bedried in about 30 minutes. For most field cor
11、es that are notcompletely saturated the drying time is generally less than 15minutes.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 flow.3.3 This method can be used for 10
12、0 mm 4 in. diameter,150 mm 6 in. diameter cylindrical, and cubical compactedbituminous specimens.3.4 This method can also be used for drying loose asphaltmixtures, aggregate samples and other solid specimens. Followmanufacturers recommended procedures for drying specimensother than compacted bitumin
13、ous 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 Vacuum Chamber, with a pump c
14、apable of evacuating asealed and enclosed chamber to a pressure of 6 mm Hg 6Torr, when at sea level. The chamber shall be large enough toaccommodate specimens of 150 mm 6 in. width or diameterand 180 mm 7 in. in height. The device shall have anautomatic vacuum, airflow and temperature control featur
15、es to1This 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 Mixtures.Current edition approved June 1, 2011. Published July 2011. DOI: 10.1520/D7227_D7227M-11.2For
16、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 ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700,
17、 West Conshohocken, PA 19428-2959, United States.ensure proper drying of the specimen at close to roomtemperatures. Automatic controls of the unit shall be calibratedby the manufacturer prior to initial use. The device shall havethe capability to display vacuum readings in the chamber andnumber of c
18、ycles.4.3 Water 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 9 F for m
19、easuring surface temperature of the speci-mens.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 PracticeD5361.6. Test Specimen6.1 To speed up the drying process, keep and main
20、tain thespecimens to be dried between 15 C and 30C 60F and85F.6.2 If desired, specimens may be separated from otherpavement layers in accordance with D5361.7. 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
21、and selftest procedures.7.2 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. 6 Torr or less. If the indicated pressureis higher than 6 mm. Hg 6 Torr, check
22、 the system for itemsthat might need service, such as oil level and quality, seals, orwater in the chamber. Refer to the manufacturers troubleshooting instructions for obtaining a proper pressure reading inthe chamber. For drying other construction materials, followmanufacturers recommendations for
23、pressure requirements inthe chamber.7.3 Drying Specimens: Use a handheld infrared thermom-eter to ensure that the surface temperature of the specimen isbetween 15C and 30C 60F and 85F. If the specimen isbelow 15C 60F or above 30C 85F, place the specimensFIG. 1 Water Removal Plate and Sample Holder I
24、nstalled in Sample ChamberD7227/D7227M 112in a room temperature environment until the surface tempera-ture approaches the required testing temperature of 15C to30C 60F and 85F.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 sp
25、ecimen on top of the specimen supportplate inside the chamber.7.3.3 Place the lid 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
26、unit will automaticallystop. The unit is calibrated at the factory to sense a “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 th
27、is pressure againstthe “dry specimen condition” pressure determined duringfactory 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 0.0004 lb or less of 24-
28、hour ovendrying at 50C 122 F.7.4 Electronic Cold Trap: Liquid and ice, or both, willaccumulate 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
29、trap. Always place the divider backinto the cold trap before drying the next specimen.8. Report8.1 Report the following information:8.1.1 At the end of the drying process, report the endingpressure in mm Hg Torr, and total number of cycles displayedon the screen. This information may be used by the
30、manufac-turer or the user for trouble shooting the device, if needed.ASTM International 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 an
31、y such patent rights, and the riskof infringement of such rights, are entirely 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 i
32、nvited either for revision of this standard or for additional standardsand should 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 receiv
33、ed a fair hearing you shouldmake your views known to the ASTM Committee on Standards, 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
34、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). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).D7227/D7227M 113
