1、Designation: D 6521 05Standard Practice forAccelerated Aging of Asphalt Binder Using a PressurizedAging Vessel (PAV)1This standard is issued under the fixed designation D 6521; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the ye
2、ar 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 practice covers the accelerated aging (oxidation) ofasphalt binders by means of pressurized air and elevat
3、edtemperature. This is intended to simulate the type of changeswhich occur in asphalt binders during in-service oxidativeaging but may not accurately simulate the relative rates ofaging. It is intended for use with residue from Test MethodD 2872 (RTFOT), which is designed to simulate plant aging.NOT
4、E 1Modified asphalt binders may phase separate or form skinsduring oven conditioning in Test Method D 2872 (RTFOT); the resultsfrom subsequent testing of this residue may not be representative ofmodified asphalts short-term aged under field conditions. Phase separa-tion, or formation of skins, or bo
5、th can also occur during PAV aging.Therefore, the practice may not be suitable for some modified asphalts.NOTE 2PAV has not been validated for materials containing particu-late materials.1.2 The aging of asphalt binders during service is affectedby ambient temperature and air pressure and by mixture
6、-associated variables, such as the volumetric proportions of themix, the permeability of the mix, properties of the aggregates,and possibly other factors. This conditioning process is in-tended to provide an evaluation of the relative resistance ofdifferent asphalt binders to oxidative aging at sele
7、cted elevatedaging temperatures and pressures, but cannot account formixture variables or provide the relative resistance to aging atin-service conditions.1.3 The values stated in SI units are to be regarded as thestandard. Values in parentheses in inch-pound units are pro-vided for informational pu
8、rposes only.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.
9、Referenced Documents2.1 ASTM Standards:2D8 Terminology Relating to Materials for Roads and Pave-mentsD 1754 Test Method for Effect of Heat and Air on AsphalticMaterials (Thin-Film Oven Test)D 2872 Test Method for Effect of Heat andAir on a MovingFilm of Asphalt (Rolling Thin-Film Oven Test)D 4753 Gu
10、ide for Evaluating, Selecting and SpecifyingBalances and Standard Masses for Use in Soil, Rock andConstruction Materials TestingD 6373 Specification for Performance Graded AsphaltBinderE 1137/E 1137M Specification for Industrial Platinum Re-sistance Thermometers2.2 AASHTO Standards:3M 320 Specificat
11、ion for Performance-Graded AsphaltBinderMP 1a Specification for Performance-Graded AsphaltBinder2.3 CGA Standards:4CGA G-7.11997 Commodity Specification for Air, FourthEdition3. Terminology3.1 Definitions:3.1.1 Definitions of terms used in this practice may be foundin Terminology D8determined from c
12、ommon English usage,or combinations of both.1This 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 15, 2005. Published August 2005. Originally
13、approved in 2000. Last previous edition approved in 2004 as D 652104.2For 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 Summary page onthe ASTM
14、website.3Available from American Association of State Highway and TransportationOfficials (AASHTO), 444 N. Capitol St., NW, Suite 249, Washington, DC 20001.4Available from Compressed Gas Association (CGA), 1725 Jefferson DavisHwy., Suite 1004, Arlington, VA 22202-4102.1Copyright ASTM International,
15、100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4. Summary of Practice4.1 Asphalt binder is first aged using Test Method D 2872(RTFOT). A specified thickness of residue from the RTFOT isthen placed in standard TFOT stainless steel pans and aged atthe specified agi
16、ng temperature for 20 h in a vessel pressurizedwith air to 2.10 MPa. Aging temperature is selected accordingto the grade of this asphalt binder. The residue is then vacuumdegassed.5. Significance and Use5.1 This practice is designed to simulate the type of in-service oxidative aging that occurs in a
17、sphalt binders duringpavement service. Residue from this conditioning practice maybe used to estimate the physical or chemical properties ofasphalt binders after several years of in-service aging in thefield.5.2 Binders aged using this practice are used to determinespecification properties in accord
18、ance with SpecificationD 6373, AASHTO M 320, or AASHTO MP 1a.5.3 For asphalt binders of different grades or from differentsources, there is no unique correlation between the aging timeand temperature in this conditioning practice and in-servicepavement age and temperature. Therefore, for a given set
19、 ofin-service climatic conditions, it is not possible to select asingle PAV aging time and elevated temperature and pressurethat will predict the properties or the relative rankings of theproperties of all asphalt binders after a specific set of in-serviceexposure conditions.5.4 The relative degree
20、of hardening of different asphaltbinders varies with aging temperatures and pressures in thePAV. Therefore, two asphalt binders may age at a similar rateat one condition of temperature and pressure, but age differ-ently at another condition. Hence, the relative rates of aging fora set of asphalts at
21、 PAV conditions may differ significantlyfrom the actual in-service relative rates at lower temperaturesand pressures.6. Apparatus6.1 An equipment system consisting of a pressure vessel,ovens, pressure-controlling devices, temperature-controllingdevices, pressure and temperature measuring devices, an
22、d atemperature and pressure recording system (see Fig. 1).6.1.1 Pressure VesselA stainless steel pressure vesseldesigned to operate at 2.1 6 0.1 MPa between 90 and 110Cwith interior dimensions adequate to hold ten TFOT pans anda pan holder. The pressure vessel shall contain a pan holdercapable of ho
23、lding ten TFOT stainless steel pans in a horizontal(level) position, such that the asphalt binder film thickness isreasonably uniform. The holder shall be designed for easyinsertion and removal from the vessel when the holder, pans,FIG. 1 Schematic of PAV Test SystemD6521052and asphalt binder are at
24、 the aging temperature. A schematicshowing a possible configuration of the vessel, pan holder andpans, and specifying dimensional requirements is shown in Fig.2.NOTE 3The vessel may be a separate unit to be placed in a forceddraft oven for conditioning the asphalt binders or an integral part of thet
25、emperature control system (for example, by direct heating of the vessel orby surrounding the vessel with a permanently affixed heating unit, forcedair oven, or liquid bath). For practical purposes, it is recommended that thevessel have the dimensions of 250 mm in diameter and 265 mm in height.Resear
26、ch has shown that the volume of the vessel is not an importantfactor in hardening due to aging.6.1.2 Pressure and Temperature Controlling Devices:6.1.2.1 A pressure relief valve that prevents pressure in thevessel from exceeding the design pressure of the vessel, but inno case exceeding 2.5 MPa duri
27、ng the aging 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 reduce the pressure from the sourceof compressed air, so that the pressure within the loadedpressure vessel is maintained at 2.1
28、6 0.1 MPa gage (relative)pressure during the aging process.6.1.2.3 A slow-release bleed valve that allows the pressurein the vessel at the completion of the conditioning procedure tobe reduced from 2.1 MPa to local atmospheric pressure within8 to 15 min.6.1.3 Temperature Controlling DeviceA digital
29、tempera-ture control device as described in 6.1.4.1 or 6.1.4.2 formaintaining the temperature during the aging procedure withinthe pressure vessel at the aging temperature 60.5C.6.1.3.1 A heating device (forced-draft oven or fluid bath)capable of restoring the aging temperature within the vesselafte
30、r loading the pans and the pan holder and prior topressurizing the vessel within2hofplacing the loaded vesselin the heating device. Maintain the temperature within thepressure vessel at the aging temperature 60.5C. If an oven isused, the oven shall have sufficiently large interior dimensionsto allow
31、 forced air to freely circulate within the oven andaround the pressure vessel when the vessel is placed in theoven. The oven shall contain a stand or shelf that supports theloaded pressure vessel in a level position above the lowersurface of the oven.6.1.3.2 A pressure vessel with an integral temper
32、ature con-trol system that is capable of restoring the pre-aging tempera-ture, as determined in , within the vessel after loading the pansand the pan holder, prior to pressurizing the vessel within 2hours of placing the loaded vessel in the heating device, andmaintaining the temperature within the p
33、ressure vessel at theaging temperature 60.5C.NOTE 4Preheating the pressure vessel may be necessary to achievethe aging temperature within the required 2-h period.6.1.4 Temperature and Pressure Measuring Devices:6.1.4.1 Aplatinum RTD accurate to the nearest 0.1C and inaccordance with Specification E
34、1137 (IEC 751), or equal, formeasuring temperature inside the pressure vessel. The RTDshall be calibrated as an integral unit with its respective metreor electronic circuitry.6.1.4.2 Temperature Recording DeviceA strip chart re-corder or other data acquisition system capable of recordingtemperature
35、throughout the aging process to within 60.1C.Asan alternative, an electronic device capable of reporting onlymaximum and minimum temperatures (accurate to 60.1C)may be used.NOTE 1Distance “a” controls the levelness of the pan. The assembly shall be supported at three or more support points. The dist
36、ance “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 b1and b2shall be such that any active portion of the temperature transducer is $10 mm from any adjacent surface.NOTE 3Distance “c” shall be
37、 $12 mm.FIG. 2 Schematic Showing Location of Pans and RTD Within PAVD65210536.1.4.3 A pressure gage capable of measuring the pressurein the pressure vessel to within 60.02 MPa during the agingprocess.6.2 Stainless Steel PansTen standard stainless steel TFOTpans that are in accordance with Test Metho
38、d D 1754.NOTE 5Stainless steel pans are required for use in the PAV becausethey provide a safer environment for hydrocarbons under elevatedtemperatures and pressures.6.3 BalanceA balance that is in accordance with GuideD 4753, Class G2.6.4 Vacuum OvenA vacuum oven capable of maintainingtemperature u
39、p to 180C with an accuracy of 65C and 15 61.0 kPa absolute pressure shall be used (see Note 6).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 65C.6.4.1.2 Vacuum Measuring Devic
40、eA vacuum gage ordigital vacuum measuring system capable of measuring theabsolute pressure in the chamber to within 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 air aspir
41、ator, or ahouse vacuum system.NOTE 6An absolute pressure of 15 6 2.5 kPa is equal to a relativepressure gage indication of 25.5 6 0.75 in. Hg at standard sea leveltemperature and pressure. This relative pressure value changes withaltitude, that is, at an altitude of 1000 m (3281 ft) the relative pre
42、ssuregage indication will be approximately -22.3 6 0.75 in. Hg at an absolutepressure of 15 6 2.5 kPa. A temperature-corrected altitude conversion forrelative pressure gage indication is to subtract 0.80 in. Hg for each 250 mof altitude (subtract 0.67 in. Hg for each 500 ft of altitude).6.6 OvenAn o
43、ven capable of maintaining a temperatureof 168 6 5C, readable to 1C.7. Materials7.1 Commercial bottled air meeting the requirements of theCGA for Grade D air, and having a maximum dew point to-40C.NOTE 7In North America, CGA Grade D air is commonly referred toas OSHA breathing air. CGA Publication G
44、-7.11997 defines Grade D airas containing 19.523.5 % oxygen, balance is predominantly nitrogen.Carbon dioxide (CO2) is limited to 1000 ppm (v/v), carbon monoxide islimited to 10 ppm and oil (condensed) to 5 mg/m3at NTP.8. Hazards8.1 Use standard laboratory safety procedures in handlingthe hot asphal
45、t binder when preparing aging specimens andremoving the residue from the pressure vessel. Use specialprecaution when lifting the pressure vessel.9. Calibration and Standardization9.1 Temperature Sensors9.1.1 PAV Temperature SensorVerify the calibration ofthe RTD and its respective meter or electroni
46、c circuitry towithin 6 0.1C at least every six months using a calibratedtemperature measuring device traceable to a national standard.Verification shall be performed near the temperature of usewithin a range of 90.0 to 110.0C. A suggested method is toperform the following steps: 1) Select a calibrat
47、ed temperaturemeasuring device with an appropriate range and prepare astirred oil bath heated to the selected verification temperature;2) Fasten the sensor to the calibrated temperature measuringdevice and place the temperature sensor and the calibratedtemperature measuring device into the stirred o
48、il bath; 3)Allowthe bath, sensor, and calibrated temperature measuring deviceto come to thermal equilibrium (the temperature in the bathshall not change by more than 0.1C per minute during theverification process); 4) Record the temperature of the cali-brated temperature measuring device and the rea
49、dout from thesensor; 5) If necessary, adjust the calibration of the digitalindicator so that the indicator and the calibrated temperaturemeasuring device indicate the same temperature, or post acorrection notice to be used in adjusting the selected agingtemperature to compensate for any error.9.1.2 Vacuum Oven Temperature SensorVerify the cali-bration of the temperature sensor used in the vacuum chamberto within 6 1C at least every six months using a calibratedtemperature measuring device traceable to a national standard.Verification shall be
