1、Designation: D7906 14Standard Practice forRecovery of Asphalt from Solution Using Toluene and theRotary Evaporator1This standard is issued under the fixed designation D7906; 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 is intended to be used to recover asphaltfrom a solvent using the rotary evaporator to ensure thatcha
3、nges in the asphalt properties during the recovery processare minimized.1.2 UnitsThe values stated in SI units are to be regardedas standard. No other units of measurement are included in thisstandard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with it
4、s 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. Referenced Documents2.1 ASTM Standards:2D92 Test Method for Flash and Fire Points by ClevelandOpen Cup TesterD2
5、172/D2172M Test Methods for Quantitative Extraction ofBitumen From Bituminous Paving MixturesD3666 Specification for Minimum Requirements for Agen-cies Testing and Inspecting Road and Paving Materials3. Summary of Practice3.1 The solution of solvent and asphalt from a prior extrac-tion is first dist
6、illed by partially immersing the rotatingdistillation flask of the rotary evaporator in a heated oil bathwhile the solution is subjected to a partial vacuum. During thefinal stage of the process, vacuum is increased and nitrogen orcarbon dioxide gas is introduced to the solution to removeremaining t
7、oluene and prevent further aging of the asphalt. Therecovered asphalt can then be tested as required.4. Significance and Use4.1 To determine the characteristics of the asphalt in anasphalt paving mixture, it is necessary to extract the asphaltfrom the aggregate by means of a suitable solvent and the
8、n torecover the asphalt from the solvent without significantlychanging the asphalts properties. The asphalt recovered fromthe solvent by this practice can be tested using the samemethods as for the original asphalt cement, and comparisonsbetween the properties of the original and recovered asphaltca
9、n be made.4.2 Users are cautioned that the recovered binder propertiesfrom an asphalt mixture sample may not exactly represent theproperties of the original asphalt binder due to factors outsideof laboratory control such as aging, contamination, and mo-lecular changes caused by exposure to heat and
10、solvents.Consequently, recovered asphalt binder properties should notbe used as a basis for acceptance.NOTE 1The quality of the results produced by this is dependent on thecompetence of the personnel performing the procedure and the capability,calibration, and maintenance of the equipment used. Agen
11、cies that meetthe criteria of Specification D3666 are generally considered capable ofcompetent and objective testing, sampling, inspection, and so forth. Usersof this practice are cautioned that compliance with Specification D3666alone does not completely assure reliable results. Reliable results de
12、pendon many factors; following the suggestions of Specification D3666 orsome similar acceptable guideline provides a means of evaluating andcontrolling some of those factors.5. Apparatus5.1 Rotary Evaporator (see Fig. 1), equipped with distilla-tion flask, variable speed motor capable of rotating th
13、e distil-lation flask at a rate of at least 40 rpm, condenser (Note 2),solvent recovery flask, and heated oil bath. The angle of thedistillation flask from the horizontal to the bath is set atapproximately 30 6 10. The distillation flask when fullyimmersed in the oil bath should be at a depth of app
14、roximately40 mm.5.2 Distillation and Receiving Flasks, a distillation flaskwith a minimum capacity of 1 L is required for the sufficientrecovery of asphalt binder. It is recommended for the receivingflask to have a minimum capacity of 1-L to maximize theamount of solvent recovery.1This practice is u
15、nder the jurisdiction of ASTM Committee D04 on Road andPaving Materials and is the direct responsibility of Subcommittee D04.25 onAnalysis of Bituminous Mixtures.Current edition approved Jan. 1, 2014. Published February 2014. DOI: 10.1520/D7906-14.2For referenced ASTM standards, visit the ASTM websi
16、te, 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.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
17、1NOTE 2Avertical condenser is recommended for solvents with higherboiling points such as toluene.5.3 Vacuum Pump and Controller, capable of maintaining avacuum of 72.0 6 0.7 kPa down to 6.7 6 0.7 kPa.5.3.1 Vacuum Controller, built into rotary evaporator systemcontrolling and measuring the specified
18、vacuum.NOTE 3Alternatively, a house vacuum system and vacuum gauge maybe used if the rotary evaporator system does not include vacuum pump andcontroller.5.4 Gas Flowmeter, capable of indicating a gas flow of up to1 L/min.5.5 Sample Container, having adequate volume to hold thesample and added solven
19、t.5.6 Digital Thermometer, capable of measuring the oil bathtemperature up to 180C with an accuracy of 61C at a depthof 40 6 5 mm.5.7 Circulating Chiller, capable of cooling circulating waterto increase condensation of toluene.NOTE 4Circulating chiller is not required if condensing water isnormally
20、below 25C, as per manufacturers recommendation. Coldercirculating water temperatures below 25C can increase the rate ofcondensation of the toluene vapor.6. Reagents and Materials6.1 Purity of ReagentsReagent-grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatal
21、l reagents conform to the specifications of the Committee onAnalytical Reagents of the American Chemical Society wheresuch specifications are available.3Other grades may be usedprovided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the acc
22、uracy ofthe determination.6.2 Nitrogen Gas or Carbon Dioxide GasA pressurizedtank with pressure-reducing valve or other convenient source.6.3 OilThe oil for the heated oil bath should be USPWhite Oil, Silicone Fluid SWS-101 with flash point above215C or an equivalent (Note 5) or high-temperature coo
23、kingoil. The flash point is determined in accordance with TestMethod D92.NOTE 5Silicone oil will expand when heated.6.4 TolueneThe solvent for extracting the asphalt from themixtures should be an ACS grade that does not have 1,2-epoxybutane as a stabilizer. The stabilizer can cause problemswith asph
24、alt containing acids.7. Hazards7.1 Toluene is a toxic solvent and should be used under ahood in a well-ventilated area to avoid high vapor levels.Consult the current Threshold Limit Concentration Committeeof the American Conference of Governmental Industrial Hy-gienists for the current threshold lim
25、it values.3Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For Suggestions on the testing of reagents notlisted by the American Chemical Society, see Annual Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States
26、Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.NOTE 1The vacuum pump and vacuum controller are recommended for maintaining the required vacuum in 5.1. The diagram displays a Bchi modelrotary evaporator.FIG. 1 Rotary Evaporator and Recovery SystemD7906 14
27、27.2 Toluene is a highly flammable substance; avoid expo-sure of the solvent to open flames and sources of ignition. Storecontainer in a cool, dry location that is well ventilated. Keepcontainer closed and sealed until ready for use. Refer to themanufacturers material safety data sheet (MSDS) for mo
28、redetailed information.8. Sampling8.1 The sample shall be obtained and handled in accordancewith Test Method A in Test Methods D2172/D2172M, with theexception that toluene will be used as the solvent. Included inthe procedure is a micro-centrifugation of the solution afterextraction to remove furthe
29、r fine particles.9. Calibration9.1 VacuumUsing a calibrated manometer or vacuumgauge, annually check vacuum pressure capable of achievingand holding a vacuum of 72.0 6 0.7 kPa down to 6.7 6 0.7kPa.9.2 Gas Flowmetershould be able to read up to 1 L/minand calibrated annually at 600 mL/min with a calib
30、ratedflowmeter.9.3 Digital ThermometerCalibrate thermometer at leastannually to read bath temperature at sample level accurately.10. Procedure10.1 Primary Distillation:10.1.1 Heat the oil bath to a temperature of 150 6 5C.Circulate cooling water through the condenser (Note 6).NOTE 6The silicone oil
31、bath temperature should be checked at theapproximate location of the submerged flask.10.1.2 While the flask is above the oil bath, draw in theasphalt-toluene solution into the distillation flask by applying avacuum of 72.0 6 0.7 kPa. Draw 200 to 300 mL of asphalt-toluene solution into the flask (Not
32、e 7). An excessive amountsolution in the flask may result in a backflow of solution intothe condenser.NOTE 7The amount of solution may be increased depending upon thesize of the distillation flask.10.1.3 Begin rotating the flask at 40 rpm and lower the flaskinto the oil. Immerse the flask approximat
33、ely 40 mm into theoil bath (Note 8). Gradually increase vacuum to 45.3 6 0.7 kPawithout causing the solution to backflow into the condenserwhile applying vacuum.NOTE 8The rotation speed of the flask may need to be reduced to 30rpm for stiffer materials. The spin rate should be lowered to expose more
34、surface area of the asphalt and dislodge more traces of the solvent from theasphalt. The 40-rpm speed could cause the asphalt to not turn in the flask,such as with a stiff binder such as PG xx-16, xx-10, recycled asphaltpavement (RAP), or recycled asphalt shingles (RAS). Exposure of a newasphalt sur
35、face enhances the diffusion of the solvent.10.1.4 Maintain 200 to 300 mL of asphalt-toluene solutionin the flask until all the solution has entered the flask.Continuously and slowly feed the solution into the distillationflask. If this cannot be done, add the solution every 3 to 5 min(Note 9).NOTE 9
36、Be cautious to not let the asphalt solution go below 200 mLuntil all the solution has been introduced to the rotary evaporator. Thiscould cause overheating and premature aging of the asphalt if the volumefalls below 200 mL.10.1.5 Remove the recovered solvent in the recovery flaskwhen needed to preve
37、nt overfill solvent into the condenser(Note 10). When emptying the recovery flask, stop intake ofthe solution into the distillation flask and release the vacuum.Release the vacuum slowly as not to cause the asphalt tobackflow into the condenser.NOTE 10Recovered solvent should not be reused with othe
38、r extrac-tions because it contains trace elements of the previous extraction.10.2 Final Distillation to Remove Remaining Solvent:10.2.1 After the bulk of the solvent has been distilled fromthe asphalt and the drip from the condenser coils is approxi-mately one drop every 15 s, slowly increase vacuum
39、 to 6.7 60.7 kPa. Hold or release vacuum if foaming or bubbling occurs.When foaming subsides, apply maximum vacuum.10.2.2 After the condensate drip rate returns to approxi-mately one drop every 15 s, turn on the nitrogen or carbondioxide gas at a flow of 600 mL/min. Maintain this conditionof nitroge
40、n or carbon dioxide gas purge and maximum vacuumfor 45 6 2 min (Note 11 and Note 12).NOTE 11The purpose of the nitrogen or carbon dioxide is to removethe oxygen from the asphalt to help reduce premature aging of the sample.NOTE 12Because of the cooling effect of the nitrogen or carbondioxide, an inc
41、rease in the oil bath temperature is generally needed tomaintain a constant sample temperature.10.2.3 At the end of the 45 min, wipe the distillation flaskclean of oil and remove from the apparatus. Inverting the flask,place into the oven at 165 6 1C to allow the asphalt binder todrain into a sample
42、 cup (Note 13).NOTE 13This temperature and time is typical for asphalts such as PG58-34s to PG 82-16s. The temperature or time or both for draining theflask will need to be increased to 180C for stiffer RAP and 200C forRAS. Not recommended to exceed 200C.11. Keywords11.1 bituminous paving mixtures;
43、RAP; RAS; recovery;recycled asphalt pavement; recycled asphalt shingles; rotaryevaporatorD7906 143ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determ
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