1、Designation: D 6925 07Standard 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 standard references notes and footnoteswhich provide explanatory material. These notes and footnotes(excluding those in tables and figures) shall not be consideredas requirements of the standard.1.4 This standard d
5、oes 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 St
6、andards: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 Compacted
7、 Bituminous MixturesD 4402 Test Method for Viscosity Determination ofAsphaltat Elevated Temperatures Using a Rotational ViscometerD 4753 Guide for Evaluating, Selecting, and SpecifyingBalances and Standard Masses for Use in Soil, Rock, andConstruction Materials Testing2.2 AASHTO Standards:3AASHTO PP
8、2 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 of Superpave Gy-ratory Compactor (SGC) Internal Angle of GyrationAASHTO T312 Preparing and Determining the Dens
9、ity 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 Methods for AsphaltConcrete53. Significance and Use3.1 This test method is used to prepare specimens fordeterminin
10、g 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 suited for the laboratory design and field control ofHMA.4. Apparatus4.1 Superpave Gyratory CompactorAn electrom
11、echani-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 for height measurement andnumber of gyrations, and (4) mold and base plate.4.1
12、.1 The reaction frame shall provide a non-compliantstructure against which the vertical loading ram can push whencompacting specimens. Reaction bearings shall be capable of1This test method is under the jurisdiction of ASTM Committee D04 on Roadand Paving Materials and is the direct responsibility o
13、f Subcommittee D04.20 onMechanical Tests of Bituminous Mixtures.Current edition approved Sept. 15, 2007. Published October 2007. Originallyapproved in 2003. Last previous edition approved in 2006 as D 6925 06.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Custom
14、er Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards 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
15、:/www.transportation.org.4Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.5Available from the Asphalt Institute (AI), 2696 Research Park Dr., Lexington,KY 40511.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box
16、C700, West Conshohocken, PA 19428-2959, United States.creating, and firmly maintaining during the compaction pro-cess, an external angle of gyration of 21.8 6 0.4 mrad (1.25 60.02 degrees).NOTE 1Research has shown external angle (measurement betweenthe external mold wall and the frame of the compact
17、or) to be differentfrom the internal angle (measurement between internal mold wall and topand bottom plate). 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 m
18、aychoose the internal angle as the basis for calibration. If internal angle ischosen for calibration the 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
19、 rotating base and drive motor shall be capable ofgyrating the specimen at a rate of 30.0 6 0.5 revolutions 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 capa
20、ble of providing and measuring a constant verticalpressure of 600 6 60 kPa during the first five gyrations, and600 6 18 kPa during the remainder of the compaction process.NOTE 2The report on the ruggedness evaluation of AASHTO TP46indicated that the pressure tolerance of 618 kPa resulted in signific
21、antlydifferent values of bulk specific gravity of the compacted specimens (Gmb)in some cases. However, since 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
22、 by pressure, operators should take care during verification ofcalibration to assure that the specified 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
23、measuring and recording the heightof the specimen during the compaction process to the nearest0.1 mm. The 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
24、Specimen MoldsSpecimen molds shall have steelwalls that are at least 7.5 mm thick and are hardened toRockwell 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 measure
25、d in accordance with ANSI B46.1).4.3 Mold Plates and Ram HeadsAll mold plates and ramheads shall be fabricated 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
26、of 149.50 mm to149.75 mm.4.4 ThermometersArmored, glass, or dial type thermom-eters with metal stems for 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
27、 g with a sensitivity of 0.1 g. The balance shallconform to Specification D 4753 as a Class GP2 balance.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
28、oven shall be available for heatingaggregates, asphalt binders, and equipment. This oven shallhave a range to a minimum of 204C, thermostatically con-trolled to 6 3C.4.7 MiscellaneousMiscellaneous equipment may include:flat bottom metal pans for heating aggregates; scoops forbatching aggregates; con
29、tainers for heating asphalt binders;mixing spoons; trowels; spatulas; welders gloves for handlinghot equipment; 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 pr
30、essure, angle of gyration, frequency ofgyration, height measurement system, and oven temperature.Verification of the mold and platen dimensions and smoothnessof finish is also required. Verification of calibration, systemstandardization, and quality checks shall be performed by themanufacturer, othe
31、r agencies providing standardization ser-vices, or in-house personnel.5.2 The equipment shall be standardized according to themanufacturers recommendations for angle, pressure, height,and rotation speed a minimum of every 100 hours use orannually, whichever is shorter. The mold and platen dimen-sion
32、s shall be standardized annually.NOTE 3Standardization should be performed if the SGC is trans-ported to a new location.NOTE 4Unknown SGC equipment should be evaluated using proce-dures described in AASHTO PP35 to assess its ability to producecompacted specimens at various compaction levels which ar
33、e 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 Compaction of Test Specimens(Laboratory Design)6.1 Preparation of AggregatesWeigh and combine theappropriate aggregate fracti
34、ons to the desired specimen weight.The 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 volumet
35、ric properties, the 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 5It may be necessary to produce a trial specimen to achievethis height requirement. Generally, 4500 to 4700 g of aggre
36、gate arerequired to achieve this height for aggregates with combined bulk specificgravities of 2.55 to 2.70 respectively. Some discrepencies in relativedensity between compactors have been resolved by adjusting the mass ofthe samples so that the compacted specimen heights are within 2 mm.NOTE 6Detai
37、ls of aggregate preparation may be found in any suitablemix design manual, such as the Asphalt Institutes MS-2.6The Superpave Gyratory Compactor, McGennis, R; Kennedy, TW; Anderson,VL; Perdomo, D, Journal of theAssociation ofAsphalt Paving Technologists Vol: 66D6925072NOTE 7The required number of gy
38、rations for purposes of determiningvolumetric 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
39、temperature.Heat the mixing container and all 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
40、 Pa-s for an asphalt binder density of 1.000g/cm3) measured in accordance with Test Method D 4402.NOTE 8Modified 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 ma
41、nufacturerto establish appropriate mixing and 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 with a spoon. Form acrater in the heated aggregate blend and weigh the requireda
42、mount of asphalt binder into the aggregate blend. Immediatelyinitiate mixing.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 f
43、or the mixingprocess.6.5 After completing the mixing process, subject the loosemix to short-term conditioning for 2 h 6 5 min at thecompaction temperature 6 3C. Stir the mix after 60 6 5 minto maintain uniform conditioning.6.6 Place a compaction mold assembly in an oven at therequired compaction tem
44、perature 65C for a minimum of 45min prior to the compaction 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
45、 of 280 6 30 mm2/s (approximately 0.28 60.03 Pa-s for an asphalt binder density of 1.000 g/cm3)measured in accordance with Test Method D 4402. See alsoNote 8.6.7 Verify the settings on the compactor. Unless notedotherwise, the SGC should be initialized to provide specimencompaction using the setting
46、s described in 4.1.6.8 At the end of the conditioning period, 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 transfe
47、rbowl 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
48、paperdisk.6.10 Load the compaction mold into the SGC and initiatethe compaction process. In most SGCs, this is an automaticprocess consisting of pressing a key to start the compactionprocess. The compactor will apply a vertical pressure, inducethe angle, and begin compaction. Compaction shall procee
49、d tothe desired endpointeither a required number of gyrations(for determination of volumetric properties), or a specifiedheight (for use in physical property testing).6.11 At the end of the compaction process, remove the moldassembly from the SGC. After a suitable cooling period,extrude the compacted specimen from the mold, and removethe paper disks.NOTE 9The purpose of the cooling period is to ensure that thespecimen will not deform when it is extruded. Cooling may be facilitatedusing a fan. For some specimens with high air voids (7 % or more) thatwill
