1、Designation: D8044 16Standard Test Method forEvaluation of Asphalt Mixture Cracking Resistance usingthe Semi-Circular Bend Test (SCB) at IntermediateTemperatures1This standard is issued under the fixed designation D8044; the number immediately following the designation indicates the year oforiginal
2、adoption or, 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 procedures for preparation,testing, and
3、measurement of asphalt mixture cracking resis-tance at Long Term Pavement Performance (LTPP) databaseintermediate temperatures using semi-circular bend (SCB)geometry laboratory prepared or pavement core asphalt mixsamples tested monotonically. The SCB sample is a half-diskwith a notch cut parallel t
4、o the loading and vertical axis. Thetest method describes the determination of the critical strainenergy release rate, Jc, and other parameters determined fromthe load-displacement curve. These parameters can be used torank the resistance of asphalt mixtures to cracking.1.2 The text of this standard
5、 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.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in th
6、isstandard.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 limitations prior to use.2. R
7、eferenced Documents2.1 ASTM Standards:2D979/D979M Practice for Sampling Bituminous PavingMixturesD2041/D2041M Test Method for Theoretical MaximumSpecific Gravity and Density of Bituminous Paving Mix-turesD2726/D2726M Test Method for Bulk Specific Gravity andDensity of Non-Absorptive Compacted Bitumi
8、nous Mix-turesD3203/D3203M Test Method for Percent Air Voids in Com-pacted Dense and Open Bituminous Paving MixturesD3666 Specification for Minimum Requirements for Agen-cies Testing and Inspecting Road and Paving MaterialsD5361/D5361M Practice for Sampling Compacted AsphaltMixtures for Laboratory T
9、estingD6373 Specification for Performance Graded AsphaltBinderD6857/D6857M Test Method for Maximum Specific Grav-ity and Density of Bituminous Paving Mixtures UsingAutomatic Vacuum Sealing MethodD6925 Test Method for Preparation and Determination ofthe Relative Density of Asphalt Mix Specimens by Me
10、ansof the Superpave Gyratory CompactorE4 Practices for Force Verification of Testing MachinesE29 Practice for Using Significant Digits in Test Data toDetermine Conformance with SpecificationsE178 Practice for Dealing With Outlying ObservationsE399 Test Method for Linear-Elastic Plane-Strain Fracture
11、Toughness KIcof Metallic MaterialsE2309/E2309M Practices for Verification of DisplacementMeasuring Systems and Devices Used in Material TestingMachinesE3029 Practice for Determining Relative Spectral Correc-tion Factors for Emission Signal of Fluorescence Spec-trometers2.2 AASHTO Standards:3R30 Prac
12、tice for Mixture Conditioning of Hot Mix Asphalt(HMA)M320 Standard Specification for Performance-Graded As-phalt BinderM332 Standard Specification for Performance-Graded UsingMultiple Stress Creep Recovery (MSCR) Test1This test method is under the jurisdiction of ASTM Committee D04 on Roadand Paving
13、 Materials and is the direct responsibility of Subcommittee D04.20 onMechanical Tests of Asphalt Mixtures.Current edition approved July 1, 2016. Published August 2016. DOI: 10.1520/D8044-16.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at servi
14、ceastm.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., NW, Suite 249, Washington, DC 20001,http:/www.transportatio
15、n.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13. Terminology3.1 Definitions:3.1.1 Jccritical strain energy release rate (kJ/m2), valueused to evaluate mixture resistance to cracking.3.1.2 Ustrain energy to failure (kJ) is the
16、area under theloading portion of the load versus deflection curves, up to themaximum load measured for each notch depth.4. Summary of Test Method4.1 A semi-circular specimen is loaded monotonically untilfracture failure occurs under a constant rate of deformation ina three-point bending load configu
17、ration. The load and defor-mation are continuously recorded and are used to compute thestrain energy for a given notch depth. The test is repeated atmultiple notch depths to compute the critical strain energyrelease rate, Jc. High Jcvalues are desirable for fracture-resistant mixtures. A Jcvalue ran
18、ging from 0.5 to 0.60 kJ/m2istypically recommended to ensure adequate fracture resistanceof the mixture.4.2 This test procedure considers the elasto-plastic/visco-elastic relationship of asphalt mixtures and fracture mechanics(Mull, et al., 2006, Anderson 2005 and suggested by Wu et al.,2005).5. Sig
19、nificance and Use5.1 The critical strain energy release rate, Jc, is used tocompare the cracking resistance of asphalt mixtures preparedwith different binder and aggregate types prepared to meet thevolumetric requirements of differing traffic levels tested atintermediate temperatures.5.2 This engine
20、ering property is a performance indicator ofintermediate temperature cracking.NOTE 1The 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 t
21、he criteria of Specification D3666 are generallyconsidered capable of competent 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; follo
22、wing the suggestions ofSpecification D3666 or some similar acceptable guideline provides ameans of evaluating and controlling some of those factors.6. Apparatus6.1 Load Test SystemA load test system consisting of anaxial loading device, environmental chamber, and control anddata acquisition system.
23、The test system shall meet the mini-mum requirements specified in Table 1. (See Practices E2309/E2309M.)6.1.1 Axial Loading DeviceThe load apparatus shall becapable of maintaining a constant deformation rate of 0.5mm/min.6.1.2 Environmental ChamberA chamber capable ofmaintaining 60.3 C of the climat
24、ic intermediate temperaturecalculated in 8.4.6.1.3 Control and Data Acquisition SystemThe systemshall include a data acquisition system comprising analog todigital conversion or digital input, or both, for storage andanalysis on a computer. The system shall be capable ofmeasuring and recording three
25、 signals during the test includingload, displacement, and chamber temperature at a samplingrate of 10 Hz. The minimum resolution of the measurements isprovided in Table 1.6.2 Measurement Devices:6.2.1 Load Measuring DeviceThe load measuring deviceshall consist of an electronic load cell, designed fo
26、r placementbetween the load platen and piston, with the minimum capacityand sensitivity stated in Table 1. The load cell shall becalibrated in accordance with Practices E4.6.2.2 Axial DeformationsAxial deformations shall bemeasured with linear variable differential transformers (LVDT)or other device
27、s capable of measuring displacement within therange and tolerance provided in Table 1. The LVDT shall becalibrated in accordance with Practice E3029, Class B.6.2.3 TemperatureChamber temperature shall be mea-sured with Resistance Temperature Detectors (RTD) or othersuitable devices accurate to withi
28、n 6 0.3C.6.3 Gyratory CompactorA gyratory compactor and asso-ciated equipment for preparing laboratory specimens in accor-dance with Test Method D6925 shall be used.6.4 SawThe saw shall be capable of producing threedifferent notch sizes ranging from 0 to 50 mm. The width of thesaw blade shall be 3.5
29、mm.6.5 Test FixtureThe loading frame shall consist of aloading rod and two sample support rods. The schematic of thetest apparatus is shown in Fig. 1. The diameters of the loadingand supports rods shall be 25 mm and the anvil span shall be127 mm.6.6 Reaction Surface TreatmentPolytetrafluoroethylene(
30、PTFE) strips are used to reduce friction between the specimenand the lower two support rollers.7. Sampling, Test Specimens, and Test Units7.1 Semi-circular bend testing may be performed on fieldcores or laboratory prepared test specimens. (See PracticesD5361/D5361M and D979/D979M.)7.2 Laboratory-com
31、pacted asphalt mixture samples:7.2.1 Specimen SizeThe specimens shall be 150 mm indiameter by 120 mm thick.7.2.2 Air Void ContentPrepare a minimum of three gyra-tory specimens at the target air void content using the Super-pave Gyratory Compactor (SGC) according to Test MethodD6925 at the target air
32、 void content 6 0.5%. The typical airvoid target for the test specimens is 7.0 %.NOTE 2The specimen air voids are calculated using Test MethodsTABLE 1 Test System Minimum RequirementsMeasurement Range AccuracyLoad Measurementand Control0to10kN 1%Displacement Measurementand Control0to30mm 0.5%Tempera
33、ture Measurementand Control Range5to35C 0.3CD8044 162D2041/D2041M, D2726/D2726M, D3203/D3203M, and D6857/D6857M.7.2.3 The semi-circular shaped specimens are prepared byfirst cutting a 150 mm diameter by 120 mm thick specimen intotwo equal circular test samples 57 mm thick. These samples arecut along
34、 its central axis into two equal semi-circular samples.The height (radius) of the two samples shall be within 1 mm ofeach other.NOTE 3Some practitioners believe that the test should be conductedon specimens with two cut faces. If this approach is used, increase thecompacted sample height by approxim
35、ately 15 6 5 mm such that thesemi-circular shaped specimens with two cut faces have a final thicknessof 57 6 1 mm.7.3 Samples Cored from Asphalt Pavement:7.3.1 Roadway cores can be used if pavement layer thick-ness is between 38 and 60 mm. Cores shall be taken full depthso that no prying action is n
36、eeded to extract the cores from thepavement. Care shall be taken to avoid stress or damage to theinterface during coring, handling, and transportation. The coresshall be trimmed such that only a single layer is tested.FIG. 1 Shop Drawing of SCB Test FixtureD8044 1637.3.2 Roadway core specimens shall
37、 be approximately150 mm diameter with all surface of the perimeter perpendicu-lar to the surface of the core within 6 mm. If the thickness ofthe core being tested is greater than 57 mm, it shall be trimmedwith a wet masonry saw to a height of 57 mm.7.3.3 The semi-circular shaped specimens are prepar
38、ed byslicing the 150 mm diameter specimen prepared in 7.2.3 alongits central axis into two equal semi-circular samples. Theheight (radius) of the two halves shall be within 1 mm of eachother.7.4 NotchingA straight vertical notch is cut along thesymmetrical axis of each semi-circular specimen. The lo
39、cationof the notch shall be in the center of the specimen within0.3 mm. The three nominal notch depths are 25 mm, 32 mm,and 38 mm. The notch depth tolerance is 6 1.0 mm. The widthof the notch shall be 3.5 mm.NOTE 4Ruggedness testing between four laboratories has shown theJcfor split samples to have
40、a within laboratory COV of 9.9 % forspecimens with notch widths between 1.3 mm and 3.4 mm. The specimensshould be symmetrical about the cut notch.7.5 AgingLaboratory-prepared test specimens shall belong term temperature-conditioned in according to AASHTOR30. Roadway cores need not be aged prior to t
41、esting.7.6 A minimum of four semi-circular specimens shall betested at each of the following notch depths: 25 mm, 32 mm,and 38 mm.NOTE 5A loose mix aging method is under development that may beable to achieve the AASHTO R30 level of aging in 12 to 24 h, NCHRP9-54 Long Term Aging of Asphalt Mixtures
42、for Performance Testing andPrediction. The long term temperature aging is needed to account forbinder source, RAP, RAS and rejuvenators on mix performance (Reinke,et al., 2009, 2015, Cooper, et al. 2014, 2015).8. Procedure8.1 Inspect the fixture to ensure all contact surfaces areclean and free of de
43、bris. Place the PTFE tape or pads to reducefriction caused by interactions between the specimen andtesting fixture during loading. The PTFE pads can be placedbetween the specimen and the bottom support rollers.8.2 Load the specimen in the fixture, ensuring the specimenis centered and making uniform
44、contact (level) on the supportrollers (as shown in Fig. 2).8.3 Set the environmental chamber temperature and allow itto stabilize to the test temperature 60.3C.Adummy specimenwith a temperature sensor mounted to its center can bemonitored to determine when the specimen reaches the testtemperature 60
45、.3C. In the absence of a dummy specimen, thespecimens should be placed in the environmental chamber setat the test temperature for a minimum of 2 6 0.5 h to reach therequired temperature equilibrium.NOTE 6Dummy specimens are typically the same material as the testspecimens.8.4 Select test temperatur
46、e based on the climatic intermedi-ate temperature performance grade temperature as defined inSpecification D6373, AASHTO M320, or M332 and providedbelow in Eq 1:PG IT 5PG HT1PG LT214 (1)where:PG IT = Intermediate performance grade temperature (C),PG HT = Climatic high performance grade temperature,
47、andPG LT = Climatic low performance grade temperature.8.5 After temperature equilibrium is reached, apply a pre-load of 45 6 10 N for a maximum duration of 30 s to specimento ensure the sample is seated properly. After ensuring thesample is level, release the load.8.6 Begin to apply load to specimen
48、 in displacement controlat a rate of 0.5 mm/min ensuring that time, force, anddisplacement are measured and recorded at a sampling rate of10 Hz. Test may be terminated when the applied load decreasesto 25 % of the peak load.9. Calculation or Interpretation of Results9.1 The critical value of J-integ
49、ral (Jc) is determined usingEq 2:Jc521bSdUdaD(2)where:Jc= critical strain energy release rate (kJ/m2),b = sample thickness (m),a = notch depth (m),U = strain energy to failure (kJ), anddU/da = change of strain energy with notch depth (kJ/m).D8044 164FIG. 2 Examples of SCB Test Fixtures for a Universal Testing Machine (a and b) and a Marshall Press (c) or AMPT (d)D8044 1659.1.1 Strain energy to failure, U, is the area under theloading portion of the load versus deflection curves, up to themaximum load measured for each notch depth (shown in Fig.3
