1、Designation:D652108D652113 Standard Practice for Accelerated Aging of Asphalt Binder Using a Pressurized Aging Vessel (PAV) 1 This standard is issued under the xed designation D6521; the number immediately following the designation indicates the year of original adoption or, in the case of revision,
2、 the year of last revision.Anumber in parentheses indicates the year of last reapproval.A superscript epsilon () indicates an editorial change since the last revision or reapproval. 1. Scope 1.1 This practice covers the accelerated aging (oxidation) of asphalt binders by means of pressurized air and
3、 elevated temperature.Thisisintendedtosimulatethechangesinrheologywhichoccurinasphaltbindersduringin-serviceoxidativeaging but may not accurately simulate the relative rates of aging. It is normally intended for use with residue from Test Method D2872 (RTFOT), which is designed to simulate plant agi
4、ng. NOTE 1Modied asphalt binders may phase separate or form skins during oven conditioning in Test Method D2872 (RTFOT); the results from subsequent testing of this residue may not be representative of modied asphalts short-term aged under eld conditions. Phase separation, or formation of skins, or
5、both can also occur during PAV conditioning. Therefore, the practice may not be suitable for some modied asphalts. NOTE 2PAV conditioning has not been validated for materials containing particulate materials. 1.2 The aging of asphalt binders during service is affected by ambient temperature and by m
6、ixture-associated variables, such asthevolumetricproportionsofthemix,thepermeabilityofthemix,propertiesoftheaggregates,andpossiblyotherfactors.This conditioning process is intended to provide an evaluation of the relative resistance of different asphalt binders to oxidative aging at selected elevate
7、d aging temperatures and pressures, but cannot account for mixture variables or provide the relative resistance to aging at in-service conditions. 1.3 The values stated in SI units are to be regarded as the standard. Values in parentheses in inch-pound units are provided for informational purposes o
8、nly. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 2. Refere
9、nced Documents 2.1 ASTM Standards: 2 D8Terminology Relating to Materials for Roads and Pavements D2872Test Method for Effect of Heat and Air on a Moving Film of Asphalt (Rolling Thin-Film Oven Test) D4753Guide for Evaluating, Selecting, and Specifying Balances and Standard Masses for Use in Soil, Ro
10、ck, and Construction Materials Testing D6373Specication for Performance Graded Asphalt Binder E1137/E1137MSpecication for Industrial Platinum Resistance Thermometers 2.2 AASHTO Standards: 3 M320Specication for Performance-Graded Asphalt Binder 2.3 CGA Standards: 4 CGA G-7.11997Commodity Specication
11、for Air, Fourth Edition 1 This practice is under the jurisdiction ofASTM Committee D04 on Road and Paving Materials and is the direct responsibility of Subcommittee D04.46 on Durability and Distillation Tests. Current edition approved Jan. 1, 2008Sept. 1, 2013. Published January 2008September 2013.
12、Originally approved in 2000. Last previous edition approved in 20052008 as D652105.D652108. DOI: 10.1520/D6521-08.10.1520/D6521-13. 2 ForreferencedASTMstandards,visittheASTMwebsite,www.astm.org,orcontactASTMCustomerServiceatserviceastm.org.ForAnnualBookofASTMStandards volume information, refer to th
13、e standards Document Summary page on the ASTM website. 3 Available from American Association of State Highway and Transportation Officials (AASHTO), 444 N. Capitol St., NW, Suite 249, Washington, DC 20001, http:/www.transportation.org. 4 Available from Compressed Gas Association (CGA), 4221 Walney R
14、d., 5th Floor, Chantilly, VA 20151-2923, http:/. This document is not anASTM standard and is intended only to provide the user of anASTM standard an indication of what changes have been made to the previous version. Because it may not be technically possible to adequately depict all changes accurate
15、ly, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version of the standard as published by ASTM is to be considered the official document. Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United State
16、s 13. Terminology 3.1 Denitions: 3.1.1 Denitions of terms used in this practice may be found in Terminology D8, determined from common English usage, or combinations of both. 4. Summary of Practice 4.1 Asphalt binder is normally rst conditioned using Test Method D2872 (RTFOT). Residue from the RTFOT
17、 is then placed in standard stainless steel pans and aged at the specied conditioning temperature for 20 h in a vessel pressurized with air to 2.10 MPa. The conditioning temperature is selected according to the grade of asphalt binder. The residue is then vacuum degassed. 5. Signicance and Use 5.1 T
18、his practice is designed to simulate the in-service oxidative aging that occurs in asphalt binders during pavement service. Residuefromthisconditioningpracticemaybeusedtoestimatethephysicalorchemicalpropertiesofasphaltbindersafterseveral years of in-service aging in the eld. 5.2 Binders conditioned
19、using this practice are normally used to determine specication properties in accordance with Specication D6373 or AASHTO M 320. 5.3 For asphalt binders of different grades or from different sources, there is no unique correlation between the time and temperature in this conditioning practice and in-
20、service pavement age and temperature. Therefore, for a given set of in-service climatic conditions, it is not possible to select a single PAV conditioning time, temperature and pressure that will predict the properties or the relative rankings of the properties of asphalt binders after a specic set
21、of in-service exposure conditions. 5.4 TherelativedegreeofhardeningofdifferentasphaltbindersvarieswithconditioningtemperaturesandpressuresinthePAV. Therefore,twoasphaltbindersmayageatasimilarrateatoneconditionoftemperatureandpressure,butagedifferentlyatanother condition. Hence, the relative rates of
22、 aging for a set of asphalts at PAV conditions may differ signicantly from the actual in-service relative rates at lower pavement temperatures and ambient pressures. 6. Apparatus 6.1 An equipment system consisting of a pressure vessel, ovens, pressure-controlling devices, temperature-controlling dev
23、ices, pressure and temperature measuring devices, and a temperature and pressure recording system (see Fig. 1). 6.1.1 Pressure VesselA stainless steel pressure vessel designed to operate at 2.1 6 0.1 MPa between 90 and 110C with interior dimensions adequate to hold ten PAVpans and a pan holder.The p
24、an holder shall be capable of holding ten PAVstainless steel pans in a horizontal (level) position, such that the asphalt binder lm thickness is reasonably uniform. The holder shall be designed for easy insertion and removal from the vessel when the holder, pans, and asphalt binder are at the condit
25、ioning temperature. A schematic showing a possible conguration of the vessel, pan holder and pans, and specifying dimensional requirements is shown in Fig. 2. NOTE3Thevesselmaybeaseparateunittobeplacedinaforceddraftovenforconditioningtheasphaltbindersoranintegralpartofthetemperature controlsystem(fo
26、rexample,bydirectheatingofthevesselorbysurroundingthevesselwithapermanentlyaffixedheatingunit,forcedairoven,orliquid bath). For practical purposes, it is recommended that the vessel have the dimensions of 250 mm in diameter and 265 mm in height. 6.1.2 Pressure and Temperature Controlling Devices: 6.
27、1.2.1 Apressure relief valve that prevents pressure in the vessel from exceeding the design pressure of the vessel, but in no case exceeding 2.5 MPa during the conditioning procedure. 6.1.2.2 Apressure regulator or regulating system capable of controlling the pressure within the vessel to60.02 MPa,
28、and with acapacityadequatetoreducethepressurefromthesourceofcompressedair,sothatthepressurewithintheloadedpressurevessel is maintained at 2.16 0.1 MPa gauge (relative) pressure during the conditioning process. 6.1.2.3 A slow-release bleed valve or pressure controller that allows the pressure in the
29、vessel at the completion of the conditioning procedure to be reduced from 2.1 MPa to local atmospheric pressure within 8 to 15 min. 6.1.3 Temperature Controlling DeviceAdigital temperature control device as described in 6.1.4.1 or 6.1.4.2 for maintaining the temperature during the conditioning proce
30、dure within the pressure vessel at the conditioning temperature60.5C. 6.1.3.1 A heating device (forced-draft oven or uid bath) capable of restoring the conditioning temperature within the vessel after loading the pans and the pan holder and prior to pressurizing the vessel within 2 h of placing the
31、loaded vessel in the heating device. The device shall be capable of maintaining the temperature within the pressure vessel at the conditioning temperature 60.5C. If an oven is used, the oven shall have sufficiently large interior dimensions to allow forced air to freely circulate within theovenandar
32、oundthepressurevesselwhenthevesselisplacedintheoven.Theovenshallcontainastandorshelfthatsupports the loaded pressure vessel in a level position above the lower surface of the oven. 6.1.3.2 A pressure vessel with an integral temperature control system that is capable of restoring the pre-conditioning
33、 temperature,asdeterminedin9.3,withinthevesselafterloadingthepansandthepanholder,priortopressurizingthevesselwithin 2 hours of placing the loaded vessel in the heating device, and maintaining the temperature within the pressure vessel at the conditioning temperature60.5C. D652113 2FIG. 1Schematic of
34、 PAV Test System NOTE 1Distance a controls the levelness of the pan. The assembly shall be supported at three or more support points. The distance a, measured from each assembly support point to the bottom of the pan (top of shelf or pan support point), shall be controlled to60.05 mm. NOTE 2Distance
35、s b 1 and b 2 shall be such that any active portion of the temperature transducer is 10 mm from any adjacent surface. NOTE 3Distance c shall be 12 mm. FIG. 2Schematic Showing Location of Pans and RTD Within PAV D652113 3NOTE 4Preheating the pressure vessel may be necessary to achieve the conditionin
36、g 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 0.1C and manufactured in accordance with Specication E1137/E1137M (IEC 751), or equal, for measuring temperature inside the p
37、ressure vessel. The RTD shall be calibrated as an integral unit with its respective metre or electronic circuitry. 6.1.4.2 TemperatureRecordingDeviceAstripchartrecorderorotherdataacquisitionsystemcapableofrecordingtemperature throughout the conditioning process to within60.1C at a minimum interval o
38、f once per minute.As an alternative, an electronic device capable of reporting only maximum and minimum temperatures (accurate to 60.1C) may be used. 6.1.4.3 Apressuregaugecapableofmeasuringthepressureinthepressurevesseltowithin60.02MPaduringtheconditioning process. 6.2 StainlessSteelPansCylindrical
39、pans,each14061mm(5.560.04in.)ininsidediameterand9.561.5mm(3/861/16 in.) deep, with a at bottom. Pans shall be manufactured of stainless steel and shall have a metal thickness of approximately 0.6 mm (0.024 in.). NOTE 5Stainless steel pans rather than aluminum pans are required for use in the PAV bec
40、ause they provide a safer environment for hydrocarbons under elevated temperatures and pressures and they are not as 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 signicantly affect the results, freque
41、nt inspection to eliminate warped or damaged pans is advisable. The indicated metal thickness has been found to provide adequate rigidity. 6.3 BalanceA balance that is in accordance with Guide D4753, Class G2. 6.4 Vacuum OvenAvacuum oven capable of maintaining temperature up to 180C with an accuracy
42、 of65C and 156 1.0 kPa absolute pressure shall be used (see Note 7). 6.4.1 Temperature and Vacuum Measuring Devices: 6.4.1.1 Temperature Measuring DeviceAtemperature sensor capable of measuring the vacuum oven chamber temperature to within65C. 6.4.1.2 Vacuum Measuring DeviceAvacuum gauge, absolute p
43、ressure gauge or digital vacuum measuring system capable of measuring the absolute pressure in the chamber to within60.5 kPa (61.0 in. Hg). 6.5 VacuumSystemAvacuumsystemcapableofgeneratingandmaintainingpressurebelow15kPaabsolute.Suitablevacuum systems include a vacuum pump, an air aspirator, or a ho
44、use vacuum system. NOTE7Avacuumgaugeprovidesthedifferenceinpressurebetweenambientatmosphericpressureandtheabsolutepressurewithinthevacuumoven. At sea level, where the atmospheric pressure is equal to 101.3 kPa (29.9 in. Hg), and with an absolute pressure inside the oven equal to 15.0 kPa (4.4 in. Hg
45、), the vacuum gauge will read 86.3 kPa (25.5 in. Hg).At an altitude of 1000 m (3281 ft) where the ambient atmospheric pressure is 89.7 kPa (26.5 in. Hg), the vacuum gauge reading will be 26.5 in. Hg minus 4.4 in. Hg or 22.1 in. Hg.Atemperature-corrected altitude conversion for relative pressure gaug
46、e indication is to subtract 0.85 in. Hg for each 250 m of altitude (subtract 0.52 in. Hg for each 500 ft of altitude). 6.6 OvenAn oven capable of maintaining a temperature of 1686 5C, readable to 1C. 7. Materials 7.1 Commercial bottled air meeting at least the minimum requirements of the CGA for Gra
47、de D air, and having a maximum dew point to -40C. NOTE 8In NorthAmerica, CGAGrade D air is commonly referred to as OSHA breathing air. CGAPublication G-7.11997 denes Grade D air as containing 19.523.5 % oxygen, balance being predominantly nitrogen. Carbon dioxide (CO 2 ) is limited to 1000 ppm (v/v)
48、, carbon monoxide is limited to 10 ppm and oil (condensed) to 5 mg/m 3 at NTP. 8. Hazards 8.1 Use standard laboratory safety procedures in handling the hot asphalt binder when preparing and conditioning specimens and removing the residue from the pressure vessel. Use special precaution when lifting
49、the pressure vessel. 9. Calibration and Standardization 9.1 Temperature Sensors 9.1.1 PAV Thermometric DeviceVerify the calibration of the thermometric device to within60.1C at least every six months usingacalibratedthermometricdevicetraceabletoanationalstandard.Vericationshallbeperformednearthetemperatureofuse within a range of 90.0 to 110.0C. NOTE 9The sensors for the thermometric devices in commercially manufactured PAV vessels cannot, or to avoid damage to the sensors and ttings, shouldn
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