1、Designation: D 7313 07Standard 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 or
2、, 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-ag
3、gregate 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 par
4、ameter 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 tempe
5、ratures 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 Materi
6、als,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 standard references notes and footnoteswhich provide explanatory material. These notes and footnotes(excluding those in tables and figures) shall not be consideredas requirement
8、s of the standard.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 standar
9、d 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 6373 Specification for Performance Graded AsphaltBinderD 6925 Test
10、 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 Plane-Strain FractureToughness KIcof Metallic MaterialsE 1823 Terminology Relating to Fatigue and Fracture Test-ing2.2
11、 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 DefinitionsTerminologies E 1823 and D8are appli-cable to this test method.3.1.1 crack mouthportion of the notch that
12、is on the flatsurface of the specimen, that is, opposite the notch tip (see Fig.3).3.1.2 crack mouth opening displacement, CMODthe rela-tive displacement of the crack mouth.3.1.3 disk-shaped compact tension geometrya geometrythat utilizes a disk-shaped specimen with a single edge notch asdescribed i
13、n Test Method E 399.3.1.4 2 fracture energy, Gfthe energy required to create aunit surface area of a crack.1This 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 edi
14、tion approved March 15, 2007. Published April 2007.2Wagoner, 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 refer
15、enced 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.4Available from American Association of State Highway and Transportatio
16、nOfficials (AASHTO), 444 N. Capitol St., 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.3.1.5 notch tipend of notch where the crack will initiateand propagate.4. Signi
17、ficance and Use4.1 The test method was developed 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 tempera
18、tures of10C (50F) or below (see Note 1). The specimen geometry isreadily adapted to 150-mm diameter specimens, such asfabricated from Superpavet gyratory compactors (Test MethodD 6925), that are used for the asphalt concrete design process.The specimen geometry can also be adapted for forensicinvest
19、igations using field cores of pavements where thin liftsare present. This geometry has been found to produce satisfac-tory results for asphalt mixtures with nominal maximumaggregates size ranging from 4.75 to 19 mm.55Wagoner, M. P., Buttlar, W. G., Paulino, G. H., and Blankenship, P., “AnInvestigati
20、on 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 theNational Academies, Washington DC, 2005, pp. 183-192.FIG. 1 Schematic of Load
21、ing ClevisD7313072NOTE 1The 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 hard
22、asphalt binder utilized in hot climates may require higher temperatures toprovide any meaningful information.5. Apparatus5.1 LoadingSpecimens shall be tested in a loading framecapable of delivering a minimum of 20 kN (4500 lb) in tension.The load apparatus shall be capable of maintaining a constantc
23、rack mouth opening displacement within 2 % of the targetvalue throughout the test. Closed-loop servo-hydraulic orservo-pneumatic test frames are highly recommended, but notrequired if the CMOD rate meets the specifications listedabove. The load cell shall have a resolution of 20 N (4.5 lb) orbetter.
24、5.2 Loading FixturesAn example of a loading clevissuitable for testing of the specimen is shown in Fig. 1. TheFIG. 2 Example of Clip-on Gage and Attachment ProceduresD7313073specimen is loaded through the pins which are allowed to rollfreely on the flat surfaces of the loading clevis. Any clevisdesi
25、gn 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 i
26、n.) 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
27、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(c)illustrates the test set-up with the specimen in the fixtures andclip-on gage attached.5.3.2 At th
28、e 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 shall havethe ability to acquire the data a
29、t 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 and water-cooling to minimize damage to
30、 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 (2FIG. 3 DC(T) Specimen DimensionsD7313074in.). The
31、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 (0.06 in.) of thelocation described i
32、n Fig. 3 and perpendicular to the faceswithin 61.5 mm (0.06 in.). The starter notch shall be no widerthan 1.5 mm (0.06 in.) with a narrower notch being highlyrecommended (see Note 2). To expedite the fabrication, alarger notch width can be used to cut up to 90 % of notchlength with the remaining cut
33、 being 1.5 mm (0.06 in.) in width.NOTE 2The 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 crack
34、 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 6
35、 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 ne
36、arest 6 0.5 mm (0.02 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 6 0.5 mm(6 0.02 in.) and averaged.7. Procedure7.1 ConditioningThe specimens shall be placed in atemperature
37、controlled chamber for a minimum of 2 h and amaximum of 16 h at the desired test temperature. The tem-perature shall be within 6 0.2C (6 0.4F) throughout theconditioning and testing times. A suggested test temperature of10C (18F) greater than the low temperature performancegrade of the asphalt binde
38、r, 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 lb).7.3 Perform test with a constant crack mouth openingdisplacement rate of 0.017 mm/s (0.00067 in./s).7.4 The
39、test is complete when the post-peak load level hasreduced to 0.1 kN (22 lb). The validity of the test is a functionof the ability to reach the specified load level (see Note 3).NOTE 3The complete failure of the specimen, that is, completeseparation of the specimen into two pieces, is not feasible du
40、e 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, the load level may never reduce to this value withinthe
41、typical range of a CMOD transducer due to crack blunting (notch tipFIG. 3 DC(T) Specimen Dimensions (continued)D7313075opening 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 wou
42、ld 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.8.1.1
43、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 1,
44、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 (60.000013in
45、./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.-lb),x = CMODfit(mm (in.),y = load (kN (lb), and
46、n = data point where load reaches 0.1 kN (22 lb).8.3 Compute fracture energy, Gf, using the following equa-tion:Gf5AREAB W a!(4)where:Gf= fracture energy (J/m2(in.-lb/in.2),AREA = area under loadCMODfitcurve (Eq 3),B = specimen thickness (m (in.), andWa = initial ligament length (m (in.).9. Report9.
47、1 Report the following information:9.1.1 Material tested (that is, nominal maximum aggregatesize, asphalt binder type, and so forth),9.1.2 Diameter, D, to the nearest 0.5 mm (0.02 in.),9.1.3 Thickness, B, to the nearest 0.5 mm (0.02 in.),9.1.4 Initial ligament length, (W-a), to the nearest 0.5 mm(0.
48、02 in.),9.1.5 Fracture energy, Gf, to the nearest 1 J/m2(0.005in.-lb/in.2),9.1.6 Peak load, to the nearest 0.1 kN (22 lb), and9.1.7 Time at peak load, to the nearest 0.1 s.FIG. 4 Example of CMOD-Time RegressionD731307610. Precision and Bias10.1 PrecisionThe within-laboratory repeatability stan-dard
49、deviation has been determined to be 78.5 J/m2(0.447in.-lb/in.2), based on 1 lab, 5 test replicates, and 2 differentsamples.6The between-laboratory reproducibility of this testmethod is being determined and will be available on or beforeDecember 2011. Therefore, this standard should not be used foracceptance or rejection of a material for purchasing purposes.10.2 BiasNo information can be presented on the bias ofthe procedure in Test Method D 7313 for measuring thefracture energy (Gf) because no material having
