1、Designation: D 7312 07Standard Test Method forDetermining the Permanent Shear Strain and ComplexShear Modulus of Asphalt Mixtures Using the SuperpaveShear Tester (SST)1This standard is issued under the fixed designation D 7312; the number immediately following the designation indicates the year ofor
2、iginal 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 standard provides performance-related test proce-dures
3、for the determination of stiffness complex shear modulusand permanent shear strain of asphalt mixtures using theSuperpave Shear Tester (SST). This standard is applicable tothe testing and analysis of modified and unmodified asphaltmixtures.1.2 This standard is applicable to specimens prepared in ala
4、boratory or cored from a pavement for post-constructionanalysis. It is intended for use with specimens having thefollowing minimum dimensions:Nominal Maximum AggregateSize in Asphalt MixtureSpecimenDiameterSpecimenHeight19 mm 150 mm 50 mm12.5 mm, 9.5 mm, 4.75 mm 150 mm 38 mmNOTE 1Nominal maximum agg
5、regate size is defined in AASH-TO R35 as one sieve larger than the first sieve to retain more than 10 %of the total aggregate. Asphalt mixtures with a nominal maximumaggregate size greater than 19 mm can be tested using this procedure, butit is not recommended. The larger aggregate sizes may signifi
6、cantlyinterfere with the material response, thereby affecting the repeatability ofthe test.NOTE 2The SST shall accommodate test specimens of 150 mm indiameter and 50 mm in height. The specimen height of 50 mm ispreferred, but may not be available in roadway cores where layerthickness may be less. If
7、 the specimen height is less than 50 mm, useplaten to platen fixturing (Linear Variable Differential Transformers(LVDTs) or extensometers). Specimen heights less than 38 mm cannot betested because of equipment constraints.NOTE 3The diameter-to-height ratio for shear test specimens shouldbe 3:1 or gr
8、eater. This effectively eliminates the use of 100 mm diameterspecimens (because of minimum height requirement for testing discussedin Note 2).1.3 The between laboratory reproducibility of this testmethod has not been determined, therefore this standard shouldnot be used for acceptance or rejection o
9、f a material forpurchasing purposes.1.4 This standard 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 limi
10、tations prior to use.2. Referenced Documents2.1 ASTM Standards:2D75 Practice for Sampling AggregatesD 140 Practice for Sampling Bituminous MaterialsD 979 Practice for Sampling Bituminous Paving MixturesD 2041 Test Method for Theoretical Maximum SpecificGravity and Density of Bituminous Paving Mixtur
11、esD 2726 Test Method for Bulk Specific Gravity and Densityof Non-Absorptive Compacted Bituminous MixturesD 3203 Test Method for Percent Air Voids in CompactedDense and Open Bituminous Paving MixturesD 3549 Test Method for Thickness or Height of CompactedBituminous Paving Mixture SpecimensD 5361 Prac
12、tice for Sampling Compacted Bituminous Mix-tures for Laboratory TestingD 6752 Test Method for Bulk Specific Gravity and Densityof Compacted Bituminous Mixtures Using AutomaticVacuum Sealing MethodD 6857 Test Method for Maximum Specific Gravity andDensity of Bituminous Paving Mixtures Using Automatic
13、Vacuum Sealing MethodD 6925 Test Method for Preparation and Determination ofthe Relative Density of Hot Mix Asphalt (HMA) Speci-mens by Means of the Superpave Gyratory CompactorE1 Specification for ASTM Liquid-in-Glass ThermometersE4 Practices for Force Verification of Testing Machines2.2 AASHTO Sta
14、ndards:31This test method is under the jurisdiction of ASTM Committee D04 on Roadand Paving Materials and is the direct responsibility of Subcommittee D04.26 onFundamental/Mechanistic Tests.Current edition approved March 1, 2007. Published March 2007.2For referenced ASTM standards, visit the ASTM we
15、bsite, 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.3Available from American Association of State Highway and TransportationOfficials (AASHTO), 444 N. Capitol St.
16、, NW, Suite 249, Washington, DC 20001,http:/www.transportation.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.AASHTO R35 Superpave Volumetric Design for Hot MixAsphalt (HMA)AASHTO R30 Short and Long Term Aging of Hot MixAsphalt
17、(HMA)3. Terminology3.1 Definitions:3.1.1 complex shear modulusa complex number that de-fines the relationship between shear stress and strain for alinear viscoelastic material, G*.3.1.2 permanent shear strainthe non-recoverable shearstrain resulting from a shear load.3.1.3 phase anglea measure of th
18、e time lag between theapplied stress and resulting strain, or applied strain andresulting stress, in a viscoelastic material.4. Summary of Test Method4.1 This test method includes two procedures.4.1.1 In the frequency sweep test, the test initiates from azero shear load and zero shear strain. Repeat
19、ed sinusoidal shearloading oscillates around zero through ten frequencies at agiven temperature while a varying axial load is applied toprevent dilation of the specimen. The loads and deformationsare used to calculate the complex shear modulus and phaseangle of the specimen at each frequency.4.1.2 I
20、n the repeated shear at constant height test, a repeatedhaversine shear stress is applied to the specimen while avarying axial load prevents dilation. The accumulated sheardeformation at the end of the test is measured to determine thepermanent shear strain.5. Significance and Use5.1 The test proced
21、ures and associated analysis techniquesdescribed in this method can be used to determine complexshear modulus and permanent shear strain of asphalt mixtures.The shear frequency sweep test at constant height can be usedto determine the complex shear modulus of a mixture. Therepeated shear test at con
22、stant height can be used to determinepermanent shear strain under repeated loading.NOTE 4The complex shear modulus is used to characterize the shearbehavior of the mixture, and the permanent shear strain relates topavement rutting.6. Apparatus6.1 Shear Test SystemThe shear test system shall consisto
23、f a loading device, specimen deformation measurementequipment, an environmental chamber, and a control and dataacquisition system. At a minimum, it shall accommodate testspecimens 150 mm in diameter and 38 to 50 mm in height.6.1.1 Loading DeviceThe loading device shall be capableof simultaneously ap
24、plying both vertical and horizontal loadsto a specimen. It shall also be capable of applying static,ramped (increasing or decreasing), and repetitive loads ofvarious waveforms. At a minimum, the loading device shall becapable of applying horizontal shear load pulses in a haversinewave form with a lo
25、ad duration of 0.1 s with 0.6 s between loadpulses. Loading shall be provided by two hydraulic actuators(one each horizontal and vertical) and shall be controlled byclosed-loop feedback using either stress or strain controlthroughout the entire range of frequencies and temperatures.The loading devic
26、e shall be capable of meeting the minimumrequirements specified in Table A1.1.6.1.2 Environmental ChamberThe environmental cham-ber shall be capable of maintaining the temperature of the testspecimen as specified in Table A1.1 during the testing se-quence.6.1.3 Data Acquisition and Control SystemThe
27、 data ac-quisition and control system shall automatically control user-selected measurement parameters, within the accuracy speci-fied in TableA1.1, during the testing sequence, and shall recordload cycles, applied horizontal and vertical loads, specimendeformation in two directions (vertical and ho
28、rizontal), envi-ronmental conditions, and the required frequency of datasampling.At the conclusion of the test, the data acquisition andcontrol system shall provide all applicable test data. The loadshall be measured by load cells, and the axial and sheardeformations shall be measured by Linear Vari
29、able DifferentialTransformers (LVDTs) meeting the requirements of TableA1.1.NOTE 5The user can view the wave or pulse parameters on theoscilloscope during the test and/or plot the raw data after the test toconfirm that the test met the user-selected load and strain levels.6.2 Conditioning ChamberThe
30、 conditioning chambershall be capable of maintaining the specimen conditioningtemperatures as specified in Table A1.1.6.3 Platen-Specimen Assembly Device (Optional)Theplaten-specimen assembly device is used to facilitate bondingthe specimen to the loading platens with adhesive. The deviceshall maint
31、ain the platens in a parallel position (relative to eachother) during the gluing operation. The platens must remainparallel so that stresses do not develop in the specimen whenthe specimen-platen assembly is clamped in the test system. Ata minimum, the device shall accommodate test specimens 150mm i
32、n diameter with a height of 38 to 50 mm.6.4 Aluminum Loading PlatensTop and bottom aluminumloading platens at least 6.35 mm greater in diameter than thediameter of the specimen to be tested and at least 20 mm thick.The bearing face of each platen shall be planar to 0.025 mmacross the entire surface.
33、6.5 AdhesiveQuick-set adhesive with a minimum hard-ened modulus of 2000 MPa for bonding the platens to thespecimen ends.NOTE 6Devcon410240 5-Minute Plastic Steel Epoxy Cement andDevcon410110 2-Hour Plastic Steel Epoxy Cement or equivalents havebeen used satisfactorily. A ruggedness experiment compar
34、ing these twoepoxies showed that glue type was not significant56.6 ThermometerA calibrated liquid-in-glass thermom-eter of suitable range with subdivisions readable to 0.1C(0.2F) or any other thermometric device of equal accuracy,precision, and sensitivity shall be used. Thermometers shallconform to
35、 the requirements of Specification E1.4”Devcon” and all its related uses and terms are trademarked and copyright ITWDevcon, 685 Galt Industrial Blvd. City: St. Louis State: MO ZIP: 63132-1021.5Anderson and McGennis, Journal of the Association of Asphalt PavingTechnologists, Vol 72, 2003.D73120727. T
36、est Specimens7.1 Prepare test specimens according to 7.2, 7.3 or 7.4,asappropriate. Test at least three specimens for each procedure (Aor B).NOTE 7Testing additional samples, typically five total, will produce amore accurate test result.7.2 Laboratory-Mixed, Laboratory-Compacted (LMLC)SpecimensSampl
37、e asphalt binder and aggregates in accor-dance with Practices D 140 and D75, respectively. Use theappropriate proportions of asphalt binder and aggregates ac-cording to the final asphalt mix design.7.2.1 Prepare aggregate batches of the appropriate mass toproduce a compacted specimen 150 mm in diame
38、ter and135 6 5 mm in height at the appropriate air void content. Heatthe aggregate batches to the appropriate mixing temperature.NOTE 8Appendix X1 contains information on the calculation of theappropriate aggregate batch weight to achieve the correct specimendimension at the proper percentage of air
39、 voids.7.2.2 Heat the asphalt binder to the appropriate mixingtemperature. Mix the correct proportions of asphalt binder andcombined aggregates to match the asphalt mix design.7.2.3 Condition the asphalt mixture for 4 h 6 5 min at 1356 3C in accordance with AASHTO R30.7.2.4 Compact the asphalt mixtu
40、re specimen following TestMethod D 6925 to produce test specimens with the required airvoids.Test Air Voids in Test SpecimenShear Frequency Sweep (Procedure A) 7.0 6 0.5 %Repeated Shear at Constant Height (Procedure B) 3.0 6 0.5 %NOTE 9Compaction procedures other than the Superpave gyratorycompactor
41、 and other target air void percentages may be used. However,the user should be careful with comparing asphalt mixtures with differenttarget air voids or compaction. The test procedures and analyses aresensitive to both the percentage of air voids and the compactionprocedure.NOTE 10Specimens are ofte
42、n compacted to a target air void percent-age that is higher than the anticipated percentage of air voids in the cut testspecimen. This is done because cutting the top and bottom of a compactedspecimen removes lower density material, thereby raising the density(lowering the air voids) of the test spe
43、cimen. The magnitude of thedifference between the target percentage of air voids for the compactedspecimen and the target percentage of air voids for the test specimen isdependent upon the nominal maximum aggregate size of the mixture,mixture gradation and other factors. Coarse mixes, and/or mixes w
44、ith alarger nominal maximum aggregate size, tend to have greater differencesbetween the compacted specimen air voids and the test specimen air voids.In general, a 1.0 % offset (compact to a target of 4.0 % air voids or 8.0 %air voids) should be sufficient to achieve the appropriate percentage of air
45、voids in the test specimen.7.2.5 Allow the compacted mixture specimens to coolcompletely to room temperature. Cut the specimens to theproper test dimensions. Determine and record the height of thetest specimens in accordance with Test Method D 3549.Toverify that the specimen faces are parallel, dete
46、rmine theminimum and maximum height of each individual specimen. Ifthe difference between the minimum and maximum height ismore than 2.0 mm, then discard that specimen and prepareanother.7.2.6 Determine the maximum specific gravity of the mix-ture in accordance with Test Method D 2041 or D 6857 and
47、thebulk specific gravity of each test specimen in accordance withTest Method D 2726 or D 6752. Calculate the air void contentof each specimen in accordance with Test Method D 3203.7.3 Field-Mixed, Laboratory-Compacted (FMLC)SpecimensObtain HMA samples in accordance with PracticeD 979. Compact specim
48、ens according to Test Method D 6925to the appropriate percentage of air voids (see 7.2.4 and Notes8-10).7.3.1 Allow the compacted mixture specimens to coolcompletely to room temperature. Cut the specimens to theproper test dimensions. Determine and record the height of thetest specimens in accordanc
49、e with Test Method D 3549.Toverify that the specimen faces are parallel, determine theminimum and maximum height of each individual specimen. Ifthe difference between the minimum and maximum height ismore than 2.0 mm, then discard that specimen and prepareanother.7.3.2 Determine the maximum specific gravity of the mix-ture in accordance with Test Method D 2041 or D 6857 and thebulk specific gravity of each test specimen in accordance withTest Method D 2726 or D 6752. Calculate the air void contentof each specimen in accordance with Test Method D 3203.7.4 Fiel
