ASTM D6925-2008 345 Standard Test Method for Preparation and Determination of the Relative Density of Hot Mix Asphalt (HMA) Specimens by Means of the Superpave Gyratory Compactor.pdf

1、Designation: D 6925 08Standard Test Method forPreparation and Determination of the Relative Density ofHot Mix Asphalt (HMA) Specimens by Means of theSuperpave Gyratory Compactor1This standard is issued under the fixed designation D 6925; the number immediately following the designation indicates the

2、 year oforiginal adoption or, in the case of revision, the year 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 test method covers the compaction of cylindri

3、calspecimens of hot mix asphalt (HMA) using the SuperpaveGyratory Compactor (SGC). This standard also refers to thedetermination of the relative density of the compacted speci-mens at any point in the compaction process. Compactedspecimens are suitable for volumetric and physical propertytesting.1.2

4、 The values stated in SI units are to be regarded as thestandard.1.3 The text of this test method references notes andfootnotes which provide explanatory material. These notes andfootnotes (excluding those in tables and figures) shall not beconsidered as requirements of the standard.1.4 This standar

5、d does not purport to address all of thesafety concerns, if any, associated 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 limitations prior to use.2. Referenced Documents2.1 ASTM

6、 Standards:2D 1188 Test Method for Bulk Specific Gravity and Densityof Compacted Bituminous Mixtures Using CoatedSamplesD 2041 Test Method for Theoretical Maximum SpecificGravity and Density of Bituminous Paving MixturesD 2726 Test Method for Bulk Specific Gravity and Densityof Non-Absorptive Compac

7、ted Bituminous MixturesD 3666 Specification for Minimum Requirements forAgen-cies Testing and Inspecting Road and Paving MaterialsD 4402 Test Method for Viscosity Determination ofAsphaltat Elevated Temperatures Using a Rotational ViscometerD 4753 Guide for Evaluating, Selecting, and SpecifyingBalanc

8、es and Standard Masses for Use in Soil, Rock, andConstruction Materials Testing2.2 AASHTO Standards:3AASHTO PP2 Practice for Short and Long Term Aging ofHot Mix Asphalt (HMA).AASHTO PP35 Provisional Practice for Evaluation of Su-perpave Gyratory Compactors (SGCs)AASHTO PP48 Practice for Evaluation o

9、f Superpave Gy-ratory Compactor (SGC) Internal Angle of GyrationAASHTO T312 Preparing and Determining the Density ofHot-Mix Asphalt (HMA) Specimens by means of theSuperpave Gyratory Compactor32.3 Other References:ANSI B46.1 American National Standards Institute4Asphalt Institute MS-2 Mix Design Meth

10、ods for AsphaltConcrete53. Significance and Use3.1 This test method is used to prepare specimens fordetermining the volumetric and physical properties of com-pacted HMA mix.3.2 This test method is useful for monitoring the density oftest specimens during the compaction process. This testmethod is su

11、ited for the laboratory design and field control ofHMA.NOTE 1The quality of the results produced by this standard aredependent on the competence of the personnel performing the procedureand the capability, calibration, and maintenance of the equipment used.Agencies that meet the criteria of Standard

12、 Practice D 3666 are generallyconsidered capable of competent and objective testing/sampling/inspection/etc. Users of this standard are cautioned that compliance withPractice D 3666 alone does not completely assure reliable results. Reliableresults depend on many factors; following the suggestions o

13、f PracticeD 3666 or some similar acceptable guideline provides a means of1This test method is under the jurisdiction of ASTM Committee D04 on Roadand Paving Materials and is the direct responsibility of Subcommittee D04.20 onMechanical Tests of Bituminous Mixtures.Current edition approved Feb. 1, 20

14、08. Published March 2008. Originallyapproved in 2003. Last previous edition approved in 2007 as D 6925 07.2For 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 standa

15、rds Document Summary page onthe ASTM website.3Available from American Association of State Highway and TransportationOfficials (AASHTO), 444 N. Capitol St., NW, Suite 249, Washington, DC 20001,http:/www.transportation.org.4Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4

16、th Floor, New York, NY 10036, http:/www.ansi.org.5Available from Asphalt Institute, 2696 Research Park Dr., Lexington, KY40511, http:/www.asphaltinstitute.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.evaluating and controlling

17、 some of those factors.4. Apparatus4.1 Superpave Gyratory CompactorAn electromechani-cal, electro-hydraulic, or electro-pneumatic compactor com-prised of the following system components: (1) reaction frame,and drive motor, (2) loading system, loading ram, and pressureindicator, (3) recording system

18、for height measurement andnumber of gyrations, and (4) mold and base plate.4.1.1 The reaction frame shall provide a non-compliantstructure against which the vertical loading ram can push whencompacting specimens. Reaction bearings shall be capable ofcreating, and firmly maintaining during the compac

19、tion pro-cess, an external angle of gyration of 21.8 6 0.4 mrad (1.25 60.02 degrees).NOTE 2Research has shown external angle (measurement betweenthe external mold wall and the frame of the compactor) to be differentfrom the internal angle (measurement between internal mold wall and topand bottom pla

20、te). The difference between these measurements varies fordifferent types of compactors. Some discrepancies in relative density havebeen resolved by use of the internal angle adjustment. Agencies maychoose the internal angle as the basis for calibration. If internal angle ischosen for calibration the

21、 recommendation of the Superpave expert taskgroup is to use an internal angle of 20.2 6 0.4 mrad (1.16 6 0.02 degrees).(See AASHTO PP48 for the procedure to determine the internal angle).4.1.2 The rotating base and drive motor shall be capable ofgyrating the specimen at a rate of 30.0 6 0.5 revoluti

22、ons perminute. The compactor shall be designed to permit the speci-men mold to gyrate freely on its tilted axis during compaction.4.1.3 The loading system, ram, and pressure indicator shallbe capable of providing and measuring a constant verticalpressure of 600 6 60 kPa during the first five gyratio

23、ns, and600 6 18 kPa during the remainder of the compaction process.NOTE 3The report on the ruggedness evaluation of AASHTO TP46indicated that the pressure tolerance of 618 kPa resulted in significantlydifferent values of bulk specific gravity of the compacted specimens (Gmb)in some cases. However, s

24、ince the pressure is directly set at 600 kPa, thetolerance of 618 kPa should apply only to the ability of the SGC tomaintain vertical pressure during compaction. To minimize potentialerrors caused by pressure, operators should take care during verification ofcalibration to assure that the specified

25、pressure has been attained.4.1.4 The axis of the loading ram shall be perpendicular tothe platen of the compactor.4.1.5 The height measurement and recording system shallbe capable of continuously measuring and recording the heightof the specimen during the compaction process to the nearest0.1 mm. Th

26、e height shall be recorded once per gyration.4.1.6 The system shall record test information, such asspecimen heights per gyration. This may be accomplishedthrough data acquisition or printing.4.2 Specimen MoldsSpecimen molds shall have steelwalls that are at least 7.5 mm thick and are hardened toRoc

27、kwell C48 or better. Molds shall have an inside diameter of149.90 mm to 150.00 mm and be at least 250 mm high. Theinside finish of the molds shall be smooth (rms of 1.60 mm orsmoother when measured in accordance with ANSI B46.1).4.3 Mold Plates and Ram HeadsAll mold plates and ramheads shall be fabr

28、icated from steel with a minimum Rockwellhardness of C48. The mold plates and ram heads shall be flat.Mold plates and ram heads (if in contact with the HMAspecimen) shall have an outside diameter of 149.50 mm to149.75 mm.4.4 ThermometersArmored, glass, or dial type thermom-eters with metal stems for

29、 determining the temperature ofaggregates, asphalt binders, and asphalt mixtures between10C and 232C, with a minimum sensitivity of 3C.4.5 BalanceThe balance shall have a minimum capacityof 10 000 g with a sensitivity of 0.1 g. The balance shallconform to Specification D 4753 as a Class GP2 balance.

30、4.6 OvensTwo ovens are recommended. One oven shallbe a forced draft oven capable of maintaining the temperaturerequired, nominally 135C, for short term aging as described in6.5. At least one more oven shall be available for heatingaggregates, asphalt binders, and equipment. This oven shallhave a ran

31、ge to a minimum of 204C, thermostatically con-trolled to 63C.4.7 MiscellaneousMiscellaneous equipment may include:flat bottom metal pans for heating aggregates; scoops forbatching aggregates; containers for heating asphalt binders;mixing spoons; trowels; spatulas; welders gloves for handlinghot equi

32、pment; 150 mm paper disks; lubricants for movingparts; laboratory timers; and mechanical mixers.5. Standardization5.1 Items requiring periodic verification of calibration in-clude the vertical pressure, angle of gyration, frequency ofgyration, height measurement system, and oven temperature.Verifica

33、tion of the mold and platen dimensions and smoothnessof finish is also required. Verification of calibration, systemstandardization, and quality checks shall be performed by themanufacturer, other agencies providing standardization ser-vices, or in-house personnel.5.2 It is required that the user ve

34、rify the calibration of thefollowing items following the manufacturers recommenda-tions: angle, pressure, height, and rotational speed.NOTE 4If no manufacturer recommendations are available, the fol-lowing schedule should be sufficient to assure the user that the SGC isoperating using the proper par

35、ameters:Angle of gyration monthlyVertical Pressure monthlyHeight Measurement System monthlyFrequency of Gyration quarterlyMold and platen dimensions annuallyCalibration shall be performed if the gyratory compactor is transportedto a new location.NOTE 5Unknown SGC equipment shall be evaluated using p

36、roce-dures described in AASHTO PP35 to assess its ability to producecompacted specimens at various compaction levels which are equivalentto two models of SGC (Pine and Troxler), which have been used by mostof the state DOTs in the past, and are known to have met thespecifications.6. Preparation and

37、Compaction of Test Specimens(Laboratory Design)6.1 Preparation of AggregatesWeigh and combine theappropriate aggregate fractions to the desired specimen weight.6The Superpave Gyratory Compactor, McGennis, R; Kennedy, TW; Anderson,VL; Perdomo, D, Journal of theAssociation ofAsphalt Paving Technologis

38、ts Vol: 66D6925082The specimen weight will vary based on the ultimate disposi-tion of the test specimens. If a target air void level is desired,specimen weights will be adjusted to create a given density ina known volume. If the specimens are to be used for determi-nation of volumetric properties, t

39、he weights will be adjusted toresult in a compacted specimen having dimensions of 150 mmin diameter and 115 6 5 mm in height at the required numberof gyrations.NOTE 6It may be necessary to produce a trial specimen to achievethis height requirement. Generally, 4500 to 4700 g of aggregate arerequired

40、to achieve this height for aggregates with combined bulk specificgravities of 2.55 to 2.70 respectively.NOTE 7Details of aggregate preparation may be found in any suitablemix design manual, such as the Asphalt Institutes MS-2.NOTE 8The required number of gyrations for purposes of determiningvolumetr

41、ic properties of an asphalt mixture specimen is based primarilyon design traffic. Table 1 shows recommended number of gyrations fordesign traffic levels.6.2 Place the blended aggregate specimens and asphaltbinder in an oven and bring to the required mixing temperature.Heat the mixing container and a

42、ll necessary mixing imple-ments to the required temperature.6.2.1 The laboratory mixing temperature range is typicallydefined as the range of temperatures where the unaged asphaltbinder has a kinematic viscosity of 170 6 20 mm2/s (approxi-mately 0.17 6 0.02 Pa-s for an asphalt binder density of 1.00

43、0g/cm3) measured in accordance with Test Method D 4402.NOTE 9Modified asphalt binders, especially those produced withpolymer additives, generally do not adhere to the equiviscous ranges notedin 6.2.1 and 6.6.1. The user should refer to the asphalt binder manufacturerto establish appropriate mixing a

44、nd compaction temperature ranges. In nocase should the mixing temperature exceed 175C.6.3 Charge the heated mixing bowl with the dry, heatedaggregate and mix the dry aggregates. Form a crater in theheated aggregate blend and weigh the required amount ofasphalt binder into the aggregate blend. Immedi

45、ately initiatemixing.6.4 Mix the asphalt binder and aggregate as quickly andthoroughly as possible to yield an asphalt mixture having auniform distribution of asphalt binder. Because of the largebatch weights, a mechanical mixer is preferable for the mixingprocess.6.5 After completing the mixing pro

46、cess, subject the loosemix to short-term conditioning for 2 h 6 5 min at thecompaction temperature 63C. Stir the mix after 60 6 5 minto maintain uniform conditioning.6.6 Place a compaction mold assembly in an oven at therequired compaction temperature 65C for a minimum of 45min prior to the compacti

47、on of the first mixture specimen(during the time the mixture is in the conditioning processdescribed in 6.5).6.6.1 The compaction temperature range is defined as therange of temperatures where the unaged asphalt binder has akinematic viscosity of 280 6 30 mm2/s (approximately 0.28 60.03 Pa-s for an

48、asphalt binder density of 1.000 g/cm3)measured in accordance with Test Method D 4402. See alsoNote 9.6.7 Verify the settings on the compactor. Unless notedotherwise, the SGC should be initialized to provide specimencompaction using the settings described in 4.1.6.8 At the end of the conditioning per

49、iod, remove the loosemix sample and the compaction mold assembly from the oven.Place a paper disk inside the mold to aid separation of thespecimen from the base plate after compaction.6.9 Quickly place the mixture into the mold using a transferbowl or other suitable device. Take care to minimize segrega-tion of the mixture in the mold. After the mixture has beencompletely loaded into the mold place a paper disk on themixture to avoid material adhering to the ram head or top moldplate. If necessary, place the top mold plate on top of the paperdisk.6.10 L