1、Designation: D6521 18Standard Practice forAccelerated Aging of Asphalt Binder Using a PressurizedAging Vessel (PAV)1This standard is issued under the fixed designation D6521; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year
2、 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 conditioning of asphalt bindersto simulate accelerated aging (oxidation) by means of pres
3、sur-ized air and elevated temperature. This is intended to simulatethe changes in rheology which occur in asphalt binders duringin-service oxidative aging, but may not accurately simulate therelative rates of aging. It is normally intended for use withresidue from Test Method D2872 (RTFOT), which is
4、 designedto simulate plant aging.NOTE 1PAV conditioning has not been validated for materialscontaining particulate materials.1.2 The aging of asphalt binders during service is affectedby ambient temperature and by mixture-associated variables,such as the volumetric proportions of the mix, the permea
5、bilityof the mix, properties of the aggregates, and possibly otherfactors. This conditioning process is intended to provide anevaluation of the relative resistance of different asphalt bindersto oxidative aging at selected elevated aging temperatures andpressures, but cannot account for mixture vari
6、ables or providethe relative resistance to aging at in-service conditions.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 The text of this standard references notes and footnoteswhich provide explanatory material. These
7、notes and footnotes(excluding those in tables and figures) shall not be consideredas requirements of the standardNOTE 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
8、equipment used.Agencies that meet the 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 ensure reliable results.Reliable
9、results depend on many factors; following the suggestions ofSpecification D3666 or some similar acceptable guideline provides ameans of evaluating and controlling some of those factors.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is the
10、responsibility of the user of this standard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.6 This international standard was developed in accor-dance with internationally recognized principles on standar
11、d-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D8 Terminology Relating to Materials for Roads a
12、nd Pave-mentsD2872 Test Method for Effect of Heat and Air on a MovingFilm of Asphalt (Rolling Thin-Film Oven Test)D3666 Specification for Minimum Requirements for Agen-cies Testing and Inspecting Road and Paving MaterialsD4753 Guide for Evaluating, Selecting, and Specifying Bal-ances and Standard Ma
13、sses for Use in Soil, Rock, andConstruction Materials TestingD6373 Specification for Performance Graded AsphaltBinderE1137/E1137M Specification for Industrial Platinum Resis-tance Thermometers2.2 AASHTO Standard:3M 320 Specification for Performance-Graded AsphaltBinder2.3 CGA Standard:4CGA G-7.11997
14、 Commodity Specification for Air, FourthEdition1This practice is under the jurisdiction of ASTM Committee D04 on Road andPaving Materials and is the direct responsibility of Subcommittee D04.46 onDurability and Distillation Tests.Current edition approved July 1, 2018. Published July 2018. Originally
15、 approvedin 2000. Last previous edition approved in 2013 as D6521 13. DOI: 10.1520/D6521-18.2For 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 S
16、ummary 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.transportation.org.4Available from Compressed Gas Association (CGA), 4221 Walney Rd., 5thFloor, Chantilly, VA 2
17、0151-2923, http:/.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDe
18、velopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.13. Terminology3.1 Definitions:3.1.1 Definitions of terms used in this practice may be foundin Terminology D8, determined from common English usage,or c
19、ombinations of both.4. Summary of Practice4.1 Asphalt binder is normally first conditioned using TestMethod D2872 (RTFOT). Residue from the RTFOT is thenplaced in standard stainless steel pans and aged at the specifiedconditioning temperature for 20 h in a vessel pressurized withair to 2.10 MPa. The
20、 conditioning temperature is selectedaccording to the grade of asphalt binder. The residue is thenvacuum degassed.5. Significance and Use5.1 This practice is designed to simulate the in-serviceoxidative aging that occurs in asphalt binders during pavementservice. Residue from this conditioning pract
21、ice may be used toestimate the physical or chemical properties of asphalt bindersafter several years of in-service aging in the field.5.2 Binders conditioned using this practice are normallyused to determine specification properties in accordance withSpecification D6373 or AASHTO M 320.5.3 For aspha
22、lt binders of different grades or from differentsources, there is no unique correlation between the time andtemperature in this conditioning practice and in-service pave-ment age and temperature. Therefore, for a given set ofin-service climatic conditions, it is not possible to select asingle PAV co
23、nditioning time, temperature, and pressure thatwill predict the properties or the relative rankings of theproperties of asphalt binders after a specific set of in-serviceexposure conditions.5.4 The relative degree of hardening of different asphaltbinders varies with conditioning temperatures and pre
24、ssures inthe PAV. Therefore, two asphalt binders may age at a similarrate at one condition of temperature and pressure, but agedifferently at another condition. Hence, the relative rates ofaging for a set of asphalts at PAV conditions may differsignificantly from the actual in-service relative rates
25、 at lowerpavement temperatures and ambient pressures.6. Apparatus6.1 An equipment system consisting of a pressure vessel,ovens, pressure controlling devices, temperature controllingdevices, pressure and temperature measuring devices, and atemperature and pressure recording system (see Fig. 1).6.1.1
26、Pressure VesselA stainless steel pressure vesseldesigned to operate at 2.1 6 0.1 MPa between 90 and 110 C,FIG. 1 Schematic of PAV Test SystemD6521 182with interior dimensions adequate to hold ten PAV pans and apan holder. The pan holder shall be capable of holding ten PAVstainless steel pans in a ho
27、rizontal (level) position, such that theasphalt binder film thickness is reasonably uniform. The holdershall be designed for easy insertion and removal from thevessel when the holder, pans, and asphalt binder are at theconditioning temperature. A schematic showing a possibleconfiguration of the vess
28、el, pan holder and pans, and specifyingdimensional requirements is shown in Fig. 2.NOTE 3The vessel may be a separate unit to be placed in aforced-draft oven for conditioning the asphalt binders or an integral partof the temperature control system (for example, by direct heating of thevessel or by s
29、urrounding the vessel with a permanently affixed heatingunit, forced air oven, or liquid bath). For practical purposes, it isrecommended that the vessel have the dimensions of 250 mm in diameterand 265 mm in height.6.1.2 Pressure and Temperature Controlling Devices:6.1.2.1 A pressure relief valve th
30、at prevents pressure in thevessel from exceeding the design pressure of the vessel, but inno case exceeding 2.5 MPa during the conditioning procedure.6.1.2.2 A pressure regulator or regulating system capable ofcontrolling the pressure within the vessel to 60.02 MPa, andwith a capacity adequate to re
31、duce the pressure from the sourceof compressed air, so that the pressure within the loadedpressure vessel is maintained at 2.1 6 0.1 MPa gauge (relative)pressure during the conditioning process.6.1.2.3 A slow-release bleed valve or pressure controllerthat allows the pressure in the vessel at the com
32、pletion of theconditioning procedure to be reduced from 2.1 MPa to localatmospheric pressure within 8 to 15 min.6.1.3 Temperature Controlling DeviceA digital tempera-ture control device as described in 6.1.4.1 or 6.1.4.2 formaintaining the temperature during the conditioning procedurewithin the pres
33、sure vessel at the conditioning temperature60.5 C.6.1.3.1 A heating device (forced-draft oven or fluid bath)capable of restoring the conditioning temperature within thevessel after loading the pans and the pan holder and prior topressurizing the vessel within2hofplacing the loaded vesselin the heati
34、ng device. The device shall be capable of maintain-ing the temperature within the pressure vessel at the condition-ing temperature 60.5 C. If an oven is used, the oven shallhave sufficiently large interior dimensions to allow forced air tofreely circulate within the oven and around the pressure vess
35、elwhen the vessel is placed in the oven. The oven shall containa stand or shelf that supports the loaded pressure vessel in alevel position above the lower surface of the oven.6.1.3.2 A pressure vessel with an integral temperature con-trol system that is capable of restoring the pre-conditioningtemp
36、erature, as determined in 9.3, within the vessel afterloading the pans and the pan holder, prior to pressurizing thevessel within2hofplacing the loaded vessel in the heatingdevice, and maintaining the temperature within the pressurevessel at the conditioning temperature 60.5 C.NOTE 4Preheating the p
37、ressure vessel may be necessary to achievethe conditioning temperature within the required 2-h period.6.1.4 Temperature and Pressure Measuring Devices:6.1.4.1 A platinum resistive thermometric device (RTD)accurate to the nearest 0.1 C and manufactured in accordancewith Specification E1137/E1137M (IE
38、C 751), or equal, formeasuring temperature inside the pressure vessel. The RTDshall be calibrated as an integral unit with its respective metreor electronic circuitry.NOTE 1Distance “a” controls the levelness of the pan. The assembly shall be supported at three or more support points. The distance “
39、a,” measuredfrom each assembly support point to the bottom of the pan (top of shelf or pan support point), shall be controlled to 60.05 mm.NOTE 2Distances “b1” and “b2” shall be such that any active portion of the temperature transducer is 10 mm from any adjacent surface.NOTE 3Distance “c” shall be
40、12 mm.FIG. 2 Schematic Showing Location of Pans and RTD Within PAVD6521 1836.1.4.2 Temperature Recording DeviceA strip chart re-corder or other data acquisition system capable of recordingtemperature throughout the conditioning process to within60.1 C at a minimum interval of once per minute. As ana
41、lternative, an electronic device capable of reporting onlymaximum and minimum temperatures (accurate to 60.1 C)may be used.6.1.4.3 A pressure gauge capable of measuring the pressurein the pressure vessel to within 60.02 MPa during theconditioning process.6.2 Stainless Steel PansCylindrical pans, eac
42、h 140 61 mm (5.5 6 0.04 in.) in inside diameter and 9.5 6 1.5 mm (386116 in.) deep, with a flat bottom. Pans shall be manufacturedof stainless steel and shall have a metal thickness of approxi-mately 0.6 mm (0.024 in.).NOTE 5Stainless steel pans, rather than aluminum pans, are requiredfor use in the
43、 PAV because they provide a safer environment forhydrocarbons under elevated temperatures and pressures and they are notas easily warped or bent.NOTE 6Pans have a tendency to become warped or bent with use.Although tests show that a slight degree of warping does not significantlyaffect the results,
44、frequent inspection to eliminate warped or damagedpans is advisable. The indicated metal thickness has been found to provideadequate rigidity.6.3 BalanceA balance that is in accordance with GuideD4753, Class G2.6.4 Vacuum OvenA vacuum oven capable of maintainingtemperature up to 180 C with an accura
45、cy of 65 C and 15 61.0 kPa absolute pressure shall be used (see Note 7).6.4.1 Temperature and Vacuum Measuring Devices:6.4.1.1 Temperature Measuring DeviceA temperaturesensor capable of measuring the vacuum oven chamber tem-perature to within 65 C.6.4.1.2 Vacuum Measuring DeviceA vacuum gauge, ab-so
46、lute pressure gauge, or digital vacuum measuring systemcapable of measuring the absolute pressure in the chamber towithin 60.5 kPa (61.0 in. Hg).6.5 Vacuum SystemA vacuum system capable of generat-ing and maintaining pressure below 15 kPa absolute. Suitablevacuum systems include a vacuum pump, an ai
47、r aspirator, or ahouse vacuum system.NOTE 7A vacuum gauge provides the difference in pressure betweenambient atmospheric pressure and the absolute pressure within thevacuum oven. At sea level, where the atmospheric pressure is equal to101.3 kPa (29.9 in. Hg), and with an absolute pressure inside the
48、 ovenequal to 15.0 kPa (4.4 in. Hg), the vacuum gauge will read 86.3 kPa(25.5 in. Hg). At an altitude of 1000 m (3281 ft) where the ambientatmospheric pressure is 89.7 kPa (26.5 in. Hg), the vacuum gauge readingwill be 26.5 in. Hg minus 4.4 in. Hg or 22.1 in. Hg. A temperature-corrected altitude con
49、version for relative pressure gauge indication is tosubtract 0.85 in. Hg for each 250 m of altitude (subtract 0.52 in. Hg foreach 500 ft of altitude).6.6 OvenAn oven capable of maintaining a temperature of168 6 5 C, readable to 1 C.7. Materials7.1 Commercial bottled air meeting at least the minimumrequirements of the CGA for Grade D air, and having amaximum dew point to 40 C.NOTE 8In North America, CGA Grade D air is commonly referred toas OSHA breathing air. CGAPublication G-7.11997 defines Grade D airas containing 19.5 to
