1、Designation: D7981 15Standard Practice forCompaction of Prismatic Asphalt Specimens by Means ofthe Shear Box Compactor1This standard is issued under the fixed designation D7981; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the y
2、ear of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers the fabrication of prismatic speci-mens of asphalt mixture using the Shear Box Compactor(S
3、BC). Compacted specimens are suitable for volumetric andphysical property testing. This standard practice should not beused for acceptance or rejection of a material or for purchasingpurposes.1.2 UnitsThe values stated in SI units are to be regardedas standard. No other units of measurement are incl
4、uded in thisstandard with exception of degrees () where angle is specified.1.3 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 determin
5、e the applica-bility of regulatory limitations prior to use.1.4 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.2. Referenced Documents2
6、.1 ASTM Standards:2D1188 Test Method for Bulk Specific Gravity and Density ofCompacted Bituminous Mixtures Using Coated SamplesD2041 Test Method for Theoretical Maximum SpecificGravity and Density of Bituminous Paving MixturesD2726 Test Method for Bulk Specific Gravity and Densityof Non-Absorptive C
7、ompacted Bituminous MixturesD3666 Specification for Minimum Requirements for Agen-cies Testing and Inspecting Road and Paving MaterialsD6752 Test Method for Bulk Specific Gravity and Densityof Compacted Bituminous Mixtures Using AutomaticVacuum Sealing MethodD6857 Test Method for Maximum Specific Gr
8、avity andDensity of Bituminous Paving Mixtures Using AutomaticVacuum Sealing MethodD6925 Test Method for Preparation and Determination ofthe Relative Density ofAsphalt Mix Specimens by Meansof the Superpave Gyratory CompactorE644 Test Methods for Testing Industrial Resistance Ther-mometers2.2 AASHTO
9、 Standards:3AASHTO TP79 Standard Method of Test for Determiningthe Dynamic Modulus and Flow Number for Hot MixAsphalt (HMA) Using the Asphalt Mixture PerformanceTesterAASHTO T321 Standard Method of Test for Determiningthe Fatigue Life of Compacted Hot Mix Asphalt (HMA)Subjected to Repeated Flexural
10、BendingAASHTO T342 Standard Method of Test for DeterminingDynamic Modulus of Hot MixAsphalt Concrete Mixtures3. Terminology3.1 Definitions:3.1.1 load cyclethe angular movement of the shearingplatens in the compactor going from the vertical position to theposition of maximum shear angle at one side,
11、then going to themaximum shear angle at the other side and back to the verticalposition (90 6 0.25 with reference to the horizontal plane).3.1.2 shear anglethe external angle measured between avertical plane (angle of 90 with respect to a horizontal plane)and the plane formed by a shearing plate in
12、the compactorwhen it has reached its maximum travel. Set at 4.4. Summary of Practice4.1 A sample of loose asphalt mixture is compacted in afully automatic apparatus by the combination of a staticvertical force and a horizontal cyclic shear force applied totwin vertical parallel platens up to a fixed
13、 maximum shearangle, to produce a prismatic specimen of compacted asphalt to1This practice is under the jurisdiction of ASTM Committee D04 on Road andPaving Materials and is the direct responsibility of Subcommittee D04.20 onMechanical Tests of Asphalt Mixtures.Current edition approved Aug. 1, 2015.
14、 Published September 2015. DOI:10.1520/D7981-15.2For 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 ASTM website.3Available fr
15、om American Association of State Highway and TransportationOfficials (AASHTO), 444 N. Capitol St., NW, Suite 249, Washington, DC 20001,http:/www.transportation.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1a target uncorrected d
16、ensity (that is, based on the geometricvolume of the specimen).5. Significance and Use5.1 Asphalt prisms compacted with the Shear Box Compac-tor can be used to obtain specimens for further testing,including bulk specific gravity following Test Methods D6752and D2726, Dynamic modulus following AASHTO
17、 T342,dynamic modulus, flow number, and flow time followingAASHTO TP79, and fatigue performance characteristics fol-lowing AASHTO T321.5.2 Specimens to perform other standard tests could also beobtained, as long as their volume is contained within thevolume of a prism having maximum width, length an
18、d height(WLH) of 150 mm, 450 mm, and 185 mm, respectively.NOTE 1The aggregate orientation in the samples produced by thismethod maybe different from samples produced by other laboratorycompaction methods. This should be considered when comparing me-chanical test results from different compaction met
19、hods.NOTE 2The 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 Specification D3666 are generallyconsidered capable of com
20、petent and objective testing/sampling/inspection/etc. Users of this standard are cautioned that compliance withSpecification D3666 alone does not completely assure reliable results.Reliable results depend on many factors chr(59). Following the sugges-tions of Specification D3666 or some similar acce
21、ptable guidelineprovides a means of evaluating and controlling some of those factors.6. Apparatus6.1 Shear Box CompactorA compactor capable of fabri-cating asphalt prisms comprised of the following systemcomponents: (1) reaction frame, (2) fully integrated loadingsystem, including loading rams, cont
22、roller and data acquisitionto record vertical force applied, height measurements andnumber of cycles, and (3) top and bottom compaction platensand wearing plates. The compactor must comply with thefollowing specifications:6.1.1 Vertical Stress adjustable by the user up to 1.0 MPa.NOTE 3The maximum v
23、ertical force required considering the speci-men dimensions should be 67.5 kN (measured and controlled to anaccuracy of 6 5% of applied load), The loading system used to achievethe required load can be electro-pneumatic, electro-mechanic, or hydrau-lic.6.1.2 Shear Force of at least 50 kN, with the c
24、apability toperform horizontal cyclic loading at a rate of 3 to 4 cyclesevery minute.6.1.3 Shear Angle fixed at 4 (6 0.25).6.1.4 The compactor must be capable of producing com-pacted prismatic specimens 450 mm (6 1.0 mm) long, 150 mm(6 1.0 mm) wide and with a height ranging from 120 mm to185 mm (6 1
25、.0 mm).6.1.5 The controller must be capable to automatically ter-minate a compaction run after meeting one of two terminationcriteria: sample height or, number of loading cycles. Thesample height and vertical load shall be recorded.6.1.6 The reaction frame shall be rigid and capable ofsustaining the
26、 maximum forces generated during the compac-tion process with system compliance of less than 0.1 mm per 1kN. It shall also be able to sustain shear reaction forces beingapplied to the mold side plates and pivots.6.1.7 The loading system (Fig. 1) shall consist of a con-FIG. 1 Example Schematics of Sh
27、ear Box Pivot PointsD7981 152trolled dual axis loading system (vertical and horizontal). Aconstant vertical force shall be applied to achieve a verticalstress as per specified above . The horizontal force shall beperpendicular to the vertical load axis, and applied through asystem that ensures the r
28、otational parallel movement of thewalls of the mold during the compaction process. The pivotpoints shall be concentrically located at both end of the moldwalls such that 62 mm of parallelism can be achieved see Fig.1.6.1.8 The horizontal loading system shall be capable ofinducing a preset constant m
29、aximum degree of rotation (maxi-mum shear angle) during a compaction of 4 (6 0.25).6.1.9 The vertical actuator or the reaction element shall slidefreely and parallel to the horizontal loading axis Fig. 2. Thevertical force applied shall be measured during the compactionprocess with suitable transduc
30、ers.6.1.10 The shear box compactor system shall also include aspecimen extraction unit.6.2 Mold Plates, Wear Plates used on top and bottom of thespecimen and Ram HeadsAll mold plates and ram headsshall be fabricated from steel with a minimum Rockwellhardness of C48. The mold plates and vertical ram
31、heads shallbe flat ( 0.1 mm over 500 mm).6.3 Loading ChuteA purpose built heat resistant chuteapproximately 445 mm long, 140 mm wide and 295 mm high,with horizontal slots near the bottom of the chute approxi-mately 75 mm apart and 75 mm tall, and with quick-releaseholding gates at the base to ensure
32、 the mix is transferreduniformly from the heating trays to the compaction moldassembled within the shear box compactor.6.4 ThermometersA platinum resistance thermometer(PRT), thermocouple, or dial-type thermometer with a range ofat least 10 to 232C. Calibrate the thermometer system (probeand readout
33、) in accordance with Test Methods E644.6.5 BalanceAt least one balance with a minimum capacityof 30 000 g with a sensitivity of 0.1 g.6.6 OvensAt least one oven, capable of achieving up to204C, and thermostatically controlled to 63C must beavailable for heating aggregates, bitumen binders, and equip
34、-ment. If short term oven aging is going to be conducted on themixture, an additional forced draft oven capable of maintainingthe requested temperature must be available.6.7 Tamping Rod or similar toolDiameter 10.0 mm,Length 450 mm, Shape Round, Material Mild steel.6.8 MiscellaneousMiscellaneous equ
35、ipment may include:flat bottom metal pans for heating aggregate and asphaltmixtures; scoops; containers for heating bituminous binders;mixing spoons; spatulas; protection gloves for handling hotequipment; portable aids to lift moderately heavy items in alaboratory setting; and mechanical mixers.7. H
36、azards7.1 This practice may involve hazardous materials, opera-tions and equipment. It does not intend to cover all the safetyconcerns associated with its use. It is the responsibility of theuser of this practice to consult and establish appropriate safetyand health practices and determine the appli
37、cability of regula-tory limitations prior to its use. Observe standard laboratorysafety precautions when preparing and testing asphalt speci-mens.8. Preparation of Apparatus8.1 Follow carefully the manufacturers recommendationsfor turning on the shear box compactor.FIG. 2 Example Schematics of Shear
38、 Box Compactor Loading SystemD7981 1538.2 If the bottom platen and bottom wear plate are notinstalled, raise the ejector to near the top of the mold and installthe bottom platen, with the wide side facing upwards, and thenplace a wear plate on top.8.3 Lower the lower platen to position it at the bot
39、tom of themold.9. Preparation and Conditioning of the Loose Mixture9.1 To prepare and condition the sample prior tocompaction, follow local or national standards for preparationof samples, adjusting the quantities of materials such that thetotal mixture produced in the laboratory or obtained from ap
40、lant is sufficient to produce the required compacted specimenvolume and a companion loose mix sample suitable to deter-mine the Theoretical Maximum Specific Gravity of the mixtureaccording to Test Method D2041 or D6857.NOTE 4For typical asphalt mixtures, the total weight required shouldbe between 20
41、 and 30 kg, depending on the density of the constituents andthe target specimen height.9.2 Place the mold plates and wearing plates in the oven atthe selected compaction temperature at least 45 min prior toloading the mix in the compactor.10. Procedure10.1 Loading a Specimen in the Shear Box Compact
42、or:10.1.1 Considering the mass required to compact the pris-matic specimens and to facilitate the transfer of the loosemixture to the compaction mold, distribute the total mass to beused during compaction in approximately equal amounts inseparate pans, ensuring that the weight of each pan is easilym
43、anageable by the person performing the compaction.NOTE 5As a general recommendation, a total of 3 to 4 pans with netweights of asphalt between 6 and 8 kg have been found to be reasonablymanageable during compaction. If splitting of the sample is not requireddue to lifting aids available in the premi
44、ses, this process can be omitted.NOTE 6Consider pouring and compacting a hot sample into the moldto allow all machine components to heat up, prior to fabricating samplesfor actual testing.NOTE 7To avoid samples sticking to the side of the mold, considerusing a release agent for rubber and polymer mo
45、dified mixes.10.1.2 Place the required mass (typically 25 to 30 kg) ofheated mix into the preheated specimen trays.10.1.3 Place the preheated loading chute on top of thecompaction mold (ensuring that the bottom gates are secured inplace).10.1.4 Using the specimen trays, feed one half of the loosemix
46、ture carefully into the chute, alternating the side of thechute into which the mix is poured in.10.1.5 Once the sample in the chute has been poured in,ensure that the mix is level and evenly spread along and acrossthe chute.NOTE 8To avoid segregation of the mix; try to achieve a uniformsurface in th
47、e chute with the least amount of intervention possible.10.1.6 Release the discharge gates in the chute to allow themix to flow into the compaction mold, and then slowly lift andremove the chute from the mold. Using a long tamping rod orsimilar tool, poke the mix five times near each of the fourverti
48、cal corners of the mold, and ensure that the specimensurface is level.10.1.7 Place the preheated loading chute back on top of thecompaction mold, repeat 10.1.4 to 10.1.6 for the second half ofthe loose mixture.10.1.8 Place the preheated wear plate and top platen withthe wider side facing downward on
49、 top of the mix. Slide themold into the frame and lock the mold to the frame followingthe instructions from the compactor manufacturer. The moldwalls shall be perpendicular (90 6 0.25 with reference to thehorizontal plane) before the compaction begins.10.2 Compaction of a Specimen:10.2.1 Enter the vertical stress to be applied during com-paction. This stress will be kept constant during the compac-tion process.NOTE 9A typical value of vertical stress suggested to be used duringcompaction is 600 kPa. Enter other specimen information as required i
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