1、Designation: D7313 13Standard Test Method forDetermining Fracture Energy of Asphalt-Aggregate MixturesUsing the Disk-Shaped Compact Tension Geometry1This standard is issued under the fixed designation D7313; the number immediately following the designation indicates the year oforiginal adoption or,
2、in the case of revision, the year 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 test method covers the determination of fractureenergy (Gf) of asphalt-aggre
3、gate 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 parame
4、ter 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 temperat
5、ures 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 E399for Plane-Strain Fracture Toughness of Metallic Materials,
6、Appendix A6, with modifications to allow fracture testing ofasphalt concrete.1.3 The test method describes the testing apparatus,instrumentation, specimen fabrication, and analysis proceduresrequired to determine fracture energy of asphalt concrete andsimilar quasi-brittle materials.1.4 The text of
7、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 test method.1.5 The values stated in SI units are to be regarded as thestandard. The values given in paren
8、theses are for informationonly.1.6 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 limitatio
9、ns prior to use.2. Referenced Documents2.1 ASTM Standards:3D8 Terminology Relating to Materials for Roads and Pave-mentsD3666 Specification for Minimum Requirements for Agen-cies Testing and Inspecting Road and Paving MaterialsD6373 Specification for Performance Graded AsphaltBinderD6925 Test Method
10、 for Preparation and Determination ofthe Relative Density of Hot Mix Asphalt (HMA) Speci-mens by Means of the Superpave Gyratory CompactorE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE399 Test Method for Linear-Elastic Plane-Strain FractureToughness KIcof Metallic Materia
11、lsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE1823 Terminology Relating to Fatigue and Fracture Testing2.2 AASHTO Standard:AASHTO T322 Standard Method of Test for Determiningthe Creep Compliance and Strength of Hot Mix Asphalt(HMA) Using the Indir
12、ect Tensile Test Device43. Terminology3.1 DefinitionsTerminologies E1823 and D8 are 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).1This test method is under the jurisdiction of ASTM Commit
13、tee D04 on Roadand Paving Materials and is the direct responsibility of Subcommittee D04.26 onFundamental/Mechanistic Tests.Current edition approved Dec. 1, 2013. Published January 2014. Originallyapproved in 2007. Last previous edition approved in 2007 as D7313 07a. DOI:10.1520/D7313-13.2Wagoner, M
14、. 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 website, www.astm.org, or
15、contact 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., NW, Suite 249, Washin
16、gton, DC 20001,http:/www.transportation.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.2 crack mouth opening displacement (CMOD) therelative displacement of the crack mouth.3.1.3 disk-shaped compact tension geometrya geometry
17、that utilizes a disk-shaped specimen with a single edge notch asdescribed in Test Method E399.3.1.4 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 d
18、eveloped for determining thefracture resistance of asphalt-aggregate 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).
19、 The specimen geometry isreadily adapted to 150 mm diameter specimens, such asfabricated from Superpave (trademark) gyratory compactorsFIG. 1 Schematic of Loading ClevisD7313 132(Test Method D6925), that are used for the asphalt concretedesign process. The specimen geometry can also be adapted forfo
20、rensic investigations using field cores of pavements wherethin lifts are present. This geometry has been found to produceFIG. 2 Example of Clip-on Gage and Attachment ProceduresD7313 133satisfactory results for asphalt mixtures with nominal maxi-mum aggregates size ranging from 4.75 to 19 mm.5NOTE 1
21、The stiffness of the asphalt binder tends to influence theassessment of a valid test as described in 7.4. For instance a soft asphaltbinder, 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
22、in hot climates may require higher temperatures toprovide any meaningful information.NOTE 2The quality of the results produced by this test method aredependent on the competence of the personnel performing the procedureand the capability, calibration, and maintenance of the equipment used.Agencies t
23、hat meet the criteria of Specification D3666 are generallyconsidered capable of competent and objective testing/sampling/inspection/etc. Users of this test method are cautioned that compliancewith Specification D3666 alone does not completely assure reliableresults. Reliable results may depend on ma
24、ny factors; following thesuggestions of Specification D3666 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. The
25、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 lo
26、ad 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 clevis5Wagoner,
27、 M. P., Buttlar, W. G., Paulino, G. H., and Blankenship, P., “AnInvestigation of the Fracture Resistance of Hot-Mix Asphalt Concrete Using aDisk-Shaped Compact Tension Test,” Transportation Research Record: Journal ofthe Transportation Research Board, No. 1929, Transportation Research Board of theNa
28、tional Academies, Washington DC, 2005, pp. 183-192.FIG. 3 DC(T) Specimen DimensionsD7313 134design 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 CMOD Displacement GageA displacement gage shallb
29、e used to measure the relative displacement of the crackmouth across two points, initially 5 mm (0.2 in.) apart. Thegage shall be attached securely to gage points, yet have theability to be released without damage if the specimen breaks.5.3.1 A recommended gage would be a clip-on gage, de-scribed in
30、 Test Method E399, which is attached to gage pointsvia knife edges. Gage points (see Fig. 2(a) shall be 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
31、(c)illustrates the test set-up with the specimen in the fixtures andclip-on gage attached.5.3.2 At the beginning of the test, the displacement gageshall have a minimum displacement of 6.35 mm (0.25 in.).5.4 Data AcquisitionTwo channels of data acquisition arerequired: load and CMOD. The acquisition
32、system shall havethe ability to acquire the data at a minimum of 25 data pointsper second.NOTE 3A third channel is recommended for temperature data acqui-sition. The acquisition system should have the ability to acquire the dataat a minimum of 25 data points per second.6. Test Specimens6.1 Test spec
33、imens 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 and water-cooling to minimize damage to the specimen.6.2.1 Specimen ThicknessThe target thickness for labora-
34、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 thickness shall be measured at four equally spacedpoints around the circumference to the nearest 60.5 mm(60.02
35、 in.) and shall not vary by more than 2.0 mm (0.079 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 in Fig. 3 and perpendicular to the faceswithin 61.5 mm (60.06 in.). The starter notch shall be nowider than
36、1.5 mm (0.06 in.) with a narrower notch beinghighly recommended (see Note 4). To expedite the fabrication,a larger notch width can be used to cut up to 90 % of notchlength with the remaining cut being 1.5 mm (0.06 in.) in width.NOTE 4The fabrication of the notch is a critical step in providing avali
37、d fracture energy values. If the notch varies significantly betweenreplicates, then the value of the fracture energy will be influenced. Thenotch length is also critical since providing a fatigue crack of a knownFIG. 3 DC(T) Specimen Dimensions (continued)D7313 135length, as recommended by Test Meth
38、od E399, is difficult to produce inthese materials. However, a notch which is relatively narrow compared tothe maximum aggregate size will produce satisfactory results.6.2.3 Flat Surface at Crack MouthThe flat surface at thecrack mouth shall be cut 90 6 5 to the notch.6.2.4 Loading HolesThe loading
39、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 nearest 60.5 mm (60.02 in.)around the circumferen
40、ce 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 controlled chamber for a minimum of 8 h and amaxi
41、mum 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, as defined in Specification D6373,is recommended
42、.7.2 After temperature conditioning, insert the specimen inloading fixtures and apply a small seating load of no greaterthan 0.2 kN (45 lbf).7.3 Perform test with a constant crack mouth openingdisplacement rate of 0.017 mm/s (0.00067 in./s).7.4 The test is complete when the post-peak load level hasr
43、educed to 0.1 kN (22 lbf). The validity of the test is a functionof the ability to reach the specified load level (see Note 5).NOTE 5The complete failure of the specimen, that is, completeseparation of the specimen into two pieces, is not feasible due to theclosed-loop control through the CMOD. If t
44、he specimen completely failswithout careful controls, the equipment could be damaged. Therefore, aminimum load limit was established to provide satisfactory test results. Athigher temperatures, the load level may never reduce to this value withinthe typical range of a CMOD transducer due to crack bl
45、unting (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 would not be valid.8. Interpretation of Fracture Energy8.1 Variability of the test results can be reduced
46、 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.8.1.1 Plot CMOD versus time (see Fig. 4).8.1.2 Use least squares regression (Eq 1) to fit a line throughthe
47、data to determine the slope (a1) and intercept (a0).Yi5 a01a1Xi(1)where:Yi= CMOD data (mm (in.),Xi= test time (s), anda0,a1= regression parameters.8.1.3 Using the regression parameters from Eq 1, create asmooth line to represent the CMOD data by using Eq 2.CMODfit5 a1Time (2)FIG. 4 Example of CMOD-T
48、ime RegressionD7313 136where: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 (60.000013in./s).8.2 Plot Load-CMODfitdata and compute the area undert
49、his curve (see Fig. 5). A suggested technique is using thequadrangle rule as shown in Eq 3.AREA 5(i51nxi112 xi!yi!10.5xi112 xi!yi112 yi! (3)where:AREA = area under loadCMODfitcurve (mm-kN (in.-lbf),x = CMODfit(mm (in.),y = load (kN (lbf), andn = data point where load reaches 0.1 kN (22 lbf).8.3 Compute fracture energy, Gf, using the following equa-tion:Gf5AREABW 2 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 len
