1、Designation: D 7313 07aStandard Test Method forDetermining Fracture Energy of Asphalt-Aggregate MixturesUsing the Disk-Shaped Compact Tension Geometry1This standard is issued under the fixed designation D 7313; the number immediately following the designation indicates the year oforiginal adoption o
2、r, 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 determination of fractureenergy (Gf) of asphalt-a
3、ggregate mixtures using the disk-shaped compact tension geometry. The disk-shaped compacttension geometry is a circular specimen with a single edgenotch loaded in tension. The fracture energy can be utilized asa parameter to describe the fracture resistance of asphaltconcrete. The fracture energy pa
4、rameter is particularly usefulin the evaluation of mixtures with ductile binders, such aspolymer-modified asphalt concrete, and has been shown todiscriminate between these materials more broadly than theindirect tensile strength parameter (AASHTO T322, Wag-oner2). The test is generally valid at temp
5、eratures of 10C(50F) and below, or for material and temperature combina-tions which produce valid material fracture, as outlined in 7.4.1.2 The specimen geometry and terminology (disk-shapedcompact tension, DC(T) is modeled after Test Method E 399for Plane-Strain Fracture Toughness of Metallic Mater
6、ials,Appendix A6, with modifications to allow fracture testing ofasphalt concrete.1.3 The test method describes the testing apparatus, instru-mentation, specimen fabrication, and analysis procedures re-quired to determine fracture energy of asphalt concrete andsimilar quasi-brittle materials.1.4 The
7、 standard unit of measurement for fracture energy isJoules/meter2(J/m2) inch-pound/inch2(in.-lbf/in.2).1.5 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 require
8、ments of the test method.1.6 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.7 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
9、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 Standards:3D8 Terminology Relating to Materials for Roads and Pave-mentsD 3666 Specification for Minimum Requirements forAgen-cies Te
10、sting and Inspecting Road and Paving MaterialsD 6373 Specification for Performance Graded AsphaltBinderD 6925 Test Method for Preparation and Determination ofthe Relative Density of Hot Mix Asphalt (HMA) Speci-mens by Means of the Superpave Gyratory CompactorE 399 Test Method for Linear-Elastic Plan
11、e-Strain FractureToughness KIcof Metallic MaterialsE 1823 Terminology Relating to Fatigue and Fracture Test-ing2.2 AASHTO Standard:AASHTO T322 Standard Method of Test for Determiningthe Creep Compliance and Strength of Hot Mix Asphalt(HMA) Using the Indirect Tensile Test Device43. Terminology3.1 Def
12、initionsTerminologies E 1823 and D8are appli-cable to this test method.3.1.1 crack mouthportion of the notch that is on the flatsurface of the specimen, that is, opposite the notch tip (see Fig.3).3.1.2 crack mouth opening displacement (CMOD)therelative displacement of the crack mouth.1This test met
13、hod 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 Dec. 1, 2007. Published January 2008. Originallyapproved in 2007. Last previous edition approved in 2007 as
14、 D 7313 07.2Wagoner, M. P., Buttlar, W. G., Paulino, G. H., and Blankenship, P., “Labora-tory Testing Suite for Characterization of Asphalt Concrete Mixtures Obtained fromField Cores,” Journal of the Association of Asphalt Paving Technologists, 2006.3For referenced ASTM standards, visit the ASTM web
15、site, 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.4Available 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.3.1.3 disk-shaped compact tension geometrya geometrythat utilizes a disk-shaped specimen with a single edge notch asdes
17、cribed in Test Method E 399.3.1.4 2 fracture energy, Gfthe energy required to create aunit surface area of a crack.3.1.5 notch tipend of notch where the crack will initiateand propagate.4. Significance and Use4.1 The test method was developed for determining thefracture resistance of asphalt-aggrega
18、te mixtures. The fractureresistance can help differentiate mixtures whose service lifemight be compromised by cracking. The test method isgenerally valid for specimens that are tested at temperatures of10C (50F) or below (see Note 1). The specimen geometry isreadily adapted to 150-mm diameter specim
19、ens, such asfabricated from Superpave (trademark) gyratory compactors(Test Method D 6925), that are used for the asphalt concretedesign process. The specimen geometry can also be adapted forforensic investigations using field cores of pavements wherethin lifts are present. This geometry has been fou
20、nd to produceFIG. 1 Schematic of Loading ClevisD 7313 07a2satisfactory results for asphalt mixtures with nominal maxi-mum aggregates size ranging from 4.75 to 19 mm.5NOTE 1The stiffness of the asphalt binder tends to influence theassessment of a valid test as described in 7.4. For instance a soft as
21、phaltbinder, which may be required for a very cold climate might not lead to amixture that would produce valid results at 10C and conversely, a hardasphalt binder utilized in hot climates may require higher temperatures toprovide any meaningful information.NOTE 2The quality of the results produced b
22、y this test method aredependent on the competence of the personnel performing the procedureand the capability, calibration, and maintenance of the equipment used.5Wagoner, M. P., Buttlar, W. G., Paulino, G. H., and Blankenship, P., “AnInvestigation of the Fracture Resistance of Hot-Mix Asphalt Concr
23、ete Using aDisk-Shaped Compact Tension Test,” Transportation Research Record: Journal ofthe Transportation Research Board, No. 1929, Transportation Research Board of theNational Academies, Washington DC, 2005, pp. 183-192.FIG. 2 Example of Clip-on Gage and Attachment ProceduresD 7313 07a3Agencies th
24、at meet the criteria of Specification D 3666 are generallyconsidered capable of competent and objective testing/sampling/inspection/etc. Users of this test method are cautioned that compliancewith Specification D 3666 alone does not completely assure reliableresults. Reliable results may depend on m
25、any factors; following thesuggestions of Specification D 3666 or some similar acceptable guidelinesprovides a means of evaluating and controlling some of those factors.5. Apparatus5.1 LoadingSpecimens shall be tested in a loading framecapable of delivering a minimum of 20 kN (4500 lbf) intension. Th
26、e load apparatus shall be capable of maintaining aconstant crack mouth opening displacement within 2 % of thetarget value throughout the test. Closed-loop servo-hydraulicor servo-pneumatic test frames are highly recommended, butnot required if the CMOD rate meets the specifications listedabove. The
27、load cell shall have a resolution of 20 N (4.5 lbf) orbetter.5.2 Loading FixturesAn example of a loading clevissuitable for testing of the specimen is shown in Fig. 1. Thespecimen is loaded through the pins which are allowed to rollfreely on the flat surfaces of the loading clevis. Any clevisdesign
28、may be used if the design demonstrates the ability toaccomplish the same result. The recommended dimensions ofthe loading clevis are shown in Fig. 1.5.3 Displacement GageAdisplacement gage shall be usedto measure the relative displacement of the crack mouth acrosstwo points, initially 5 mm (0.2 in.)
29、 apart. The gage shall beattached securely to gage points, yet have the ability to bereleased without damage if the specimen breaks.5.3.1 A recommended gage would be a clip-on gage, de-scribed in Test Method E 399, which is attached to gage pointsvia knife edges. Gage points (see Fig. 2(a) shall be
30、glued to thespecimen so that the clip-on gage is set to the proper gagelength, which is typically 5 mm (0.2 in.). Fig. 2(b) illustratesthe attachment of the clip-on gage to the gage points. Fig. 2(c)illustrates the test set-up with the specimen in the fixtures andclip-on gage attached.FIG. 3 DC(T) S
31、pecimen DimensionsD 7313 07a45.3.2 At the beginning of the test, the displacement gageshall have a minimum displacement of 6.35 mm (0.25 in.). Theresolution shall be within 0.1 % of full scale.5.4 Data AcquisitionTwo channels of data acquisition arerequired: load and CMOD. The acquisition system sha
32、ll havethe ability to acquire the data at a minimum of 25 data pointsper second.6. Test Specimens6.1 Test specimens shall be fabricated in accordance withthe dimensions shown in Fig. 3.6.2 Specimen FabricationThe equipment used for speci-men fabrication shall utilize diamond-impregnated cuttingfaces
33、 and water-cooling to minimize damage to the specimen.6.2.1 Specimen ThicknessThe target thickness for labora-tory compacted specimens shall be 50 6 5mm(26 0.2 in.).The target thickness for field cores should be the lift thicknessor 50 6 5mm(26 0.2 in.) if the lift is greater than 50 mm (2in.). The
34、thickness shall be measured at four equally spacedpoints around the circumference to the nearest 60.5 mm(60.02 in.) and shall not vary by more than 2.5 mm (0.1 in.).6.2.2 NotchThe starter notch shall be fabricated along thediameter of the specimen within 61.5 mm (60.06 in.) of thelocation described
35、in Fig. 3 and perpendicular to the faceswithin 61.5 mm (60.06 in.). The starter notch shall be nowider than 1.5 mm (0.06 in.) with a narrower notch beinghighly recommended (see Note 3). To expedite the fabrication,a larger notch width can be used to cut up to 90 % of notchlength with the remaining c
36、ut being 1.5 mm (0.06 in.) in width.NOTE 3The fabrication of the notch is a critical step in providing avalid fracture energy. If the notch varies significantly between replicates,then the value of the fracture energy will be influenced. The notch lengthis also critical since providing a fatigue cra
37、ck of a known length, asrecommended by Test Method E 399, is difficult to produce in thesematerials. However, a notch which is relatively narrow compared to themaximum aggregate size will produce satisfactory results.6.2.3 Flat Surface at Crack MouthThe flat surface at thecrack mouth shall be cut 90
38、 6 5 to the notch.6.2.4 Loading HolesThe loading holes shall be fabricated90 6 5 to the faces of the specimen. The location of theloading holes shall not be greater than 5 mm (0.2 in.) from thespecified locations.6.2.5 Specimen Diameter, DMeasurements shall be takenat no less than two points to the
39、nearest 60.5 mm (60.02 in.)around the circumference of the specimen and then averaged.6.2.6 Initial ligament length, (W-a)Measurements shall betaken on both sides of the specimen to the nearest 60.5 mm(60.02 in.) and averaged.7. Procedure7.1 ConditioningThe specimens shall be placed in atemperature
40、controlled chamber for a minimum of 2 h and amaximum of 16 h at the desired test temperature. The tem-perature shall be within 60.2C (60.4F) throughout theconditioning and testing times. A suggested test temperature of10C (18F) greater than the low temperature performancegrade of the asphalt binder,
41、 as defined in Specification D 6373,is recommended.7.2 After temperature conditioning, insert the specimen inloading fixtures and apply a small seating load of no greaterthan 0.2 kN (45 lbf).FIG. 3 DC(T) Specimen Dimensions (continued)D 7313 07a57.3 Perform test with a constant crack mouth openingdi
42、splacement rate of 0.017 mm/s (0.00067 in./s).7.4 The test is complete when the post-peak load level hasreduced to 0.1 kN (22 lbf). The validity of the test is a functionof the ability to reach the specified load level (see Note 4).NOTE 4The complete failure of the specimen, that is, completeseparat
43、ion of the specimen into two pieces, is not feasible due to theclosed-loop control through the CMOD. If the specimen completely failswithout careful controls, the equipment could be damaged. Therefore, aminimum load limit was established to provide satisfactory test results. Athigher temperatures, t
44、he load level may never reduce to this value withinthe typical range of a CMOD transducer due to crack blunting (notch tipopening without crack growth). In this case, the fracture energy may notbe the dominate source of energy consumption and the test analysismethods presented in this specification
45、would not be valid.8. Interpretation of Fracture Energy8.1 Variability of the test results can be reduced by datasmoothing or elimination of extraneous electronic noise cap-tured during the test. The following procedures outline amethod to reduce the electronic noise associated with theCMOD data.8.1
46、.1 Plot CMOD versus time (see Fig. 4).8.1.2 Use least squares regression (Eq 1) to fit a line throughthe data to determine the slope (a1) and intercept (a0).Yi5 a01 a1 Xi(1)where:Yi= CMOD data (mm (in.),Xi= test time (s), anda0,a1= regression parameters.8.1.3 Using the regression parameters from Eq
47、1, create asmooth line to represent the CMOD data by using Eq 2.CMODfit5 a1 Time (2)where:CMODfit= smoothed CMOD data (mm (in.),a1= slope of line (mm/s (in./s), andTime = Xifrom Eq 1.8.1.4 For a valid test, the rate (a1) shall be within 2 % of theexpected rate defined in 7.3 (60.00034 mm/s (60.00001
48、3in./s).8.2 Plot Load-CMODfitdata and compute the area underthis curve (see Fig. 5). A suggested technique is using thequadrangle rule as shown in Eq 3.AREA 5(i51nxi11 xi! yi! 1 0.5 xi11 xi! yi11 yi! (3)where:AREA = area under loadCMODfitcurve (mm-kN (in.-lbf),x = CMODfit(mm (in.),y = load (kN (lbf)
49、, andn = data point where load reaches 0.1 kN (22 lbf).8.3 Compute fracture energy, Gf, using the following equa-tion:Gf5AREAB W a!(4)where:Gf= fracture energy (J/m2(in.-lbf/in.2),AREA = area under loadCMODfitcurve (Eq 3),B = specimen thickness (m (in.), andWa = initial ligament length (m (in.).9. Report9.1 Report the following information:9.1.1 Material tested (that is, nominal maximum aggregatesize, asphalt binder type, and so forth),FIG. 4 Example of CMOD-Time RegressionD 7313 07a69.1.2 Diameter, D, to
