1、Designation: D6703 13Standard Test Method forAutomated Heithaus Titrimetry1This standard is issued under the fixed designation D6703; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parenthese
2、s indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method describes a procedure for quantifyingthree Heithaus compatibility parameters that quantify thecolloidal stability of asphalts and asphalt
3、cross blends and agedasphalts.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 its use. It is theresponsibility of the user
4、 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:2D3279 Test Method forn-Heptane InsolublesD4124 Test Method for Separation of Asphalt into FourFractionsD5546 Test
5、 Method for Solubility of Asphalt Binders inToluene by CentrifugeE169 Practices for General Techniques of Ultraviolet-VisibleQuantitative Analysis3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 asphalt binder, nasphalt which may or may notcontain an asphalt modifier (see aspha
6、lt modifier).3.1.1.1 DiscussionThis term is often used in the Perfor-mance Graded Binder system.3.1.2 asphalt cross-blend, nany mixture of two or moreasphalts blended together to form a consistent material.3.1.3 asphaltene peptizability, nthe tendency of as-phaltenes to exist as a stable dispersion
7、in a maltene solvent,measured by the Heithaus parameter pa.3.1.4 asphaltene, ninsoluble fractions of asphalt that areprecipitated by use of selected solvents, such as n-heptane.3.1.5 asphalt state of peptization, na measure of theability of the combination of a maltene solvent and dispersedasphalten
8、es to form a stable dispersed system.3.1.6 colloidal suspension, nan intimate mixture of twosubstances, one of which, called the dispersed phase (orcolloid), is uniformly distributed in a finely divided statethrough the second substance, called the dispersion medium (ordispersing medium).3.1.7 compa
9、tibility, nthe state of peptization of an asphalt,which is measured quantitatively by the Heithaus parameter P.3.1.8 dispersed phase, none phase of a dispersion consist-ing of particles or droplets of one substance distributed througha second phase.3.1.9 dispersing medium, none phase of a dispersion
10、 thatdistributes particles or droplets of another substance, thedisperse phase.3.1.10 flocculation, nthe process of aggregation and co-alescence into a flocculent mass.3.1.11 Heithaus compatibility parameters, nthree param-eters: asphaltene peptizability (pa), maltene peptizing power(po), and asphal
11、t state of peptization (P), measured usingHeithaus titration methods.3.1.12 maltene, nsoluble fractions of asphalt that arerecovered from an eluate by use of selected solvents, such asn-heptane.3.1.13 maltene peptizing power, nthe ability of a maltenesolvent to disperse asphaltenes, measured by the
12、Heithausparameter po.4. Summary of Test Method4.1 Three 40 mL reaction vials are tared. Three samples ofasphalt of weights 0.400 g, 0.600 g and 0.800 g are transferredto each of three reaction vials. Toluene (3.000 mL) is added toeach reaction vial to dissolve the asphalt constituting threesolutions
13、 which differ by concentration. Each solution is1This test method is under the jurisdiction of ASTM Committee D04 on Roadand Paving Materials and is the direct responsibility of Subcommittee D04.47 onMiscellaneous Asphalt Tests.Current edition approved Dec. 1, 2013. Published February 2014. Original
14、lyapproved in 2001. Last previous edition approved in 2007 as D6703 07. DOI:10.1520/D6703-13.2For 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
15、Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1titrated with isooctane (2,2,4-trimethyl pentane) to promoteonset of flocculation of the solution.4.2 Titrations are performed by placing reaction vials s
16、epa-rately in the apparatus illustrated in Fig. 1. Each reaction vialis separately placed into a 250 mL water-jacketed reactionvessel (Fig. 1) to provide temperature control of the system.The sample circulation loop is made by pumping the solutionthrough a short path length quartz flow cell housed i
17、n anultraviolet-visible spectrophotometer then back to the reactionvial with high flow rate metering pump. A second reactionvessel is filled with titrant is placed into a second 250 mLwater-jacketed reaction vessel. A titration loop is made bypumping titrant into the sample reaction vial at a consta
18、nt flowrate using a low flow rate metering pump. During a titration theoutput signal from the spectrophotometer is recorded using aData acquisition system (computer) to record the change inpercent transmittance (%T) of detected radiation at 740 nmpassing through the quartz cell plotted versus time,
19、t, duringwhich the titrant.4.3 The spectrophotometer output signal measures turbidityof the sample solution as a titration experiment proceeds to aflocculation onset point, corresponding to the onset of floccu-lating asphaltene phase separating from the solution. Fig. 2illustrates a plot of %T versu
20、s t for three test solutions. Valuesof %T are observed to increase with time to the flocculationonset point, after which values of %T are observed to decrease.The time required to reach flocculation onset tfmultiplied bythe titrant flow rate gives the titrant flocculation volume VT.4.4 Given the wei
21、ghts of each asphalt sample, Wa, thevolume of toluene initially used to dissolve each sample VSandthe volume of titrant at onset of flocculation VT, values of Creferred to as the dilution concentration and FR referred to asthe flocculation ratio are calculated as C = Wa/(VS+ VT) and FR= VS/(VS+ VT).
22、 Values of C plotted along an x-axis versus FRplotted along a y-axis result in a linear regression line (Fig. 3).This line is extrapolated to both axes. The point at which theline intercepts the x-axis is defined as Cmin. The point at whichthe line intercepts the y-axis is defined as FRmax. These tw
23、ovalues are used to calculate the three Heithaus compatibilityparameters, designated pa, po, and P. The parameter pa, thepeptizability of asphaltenes, is defined as the quantity (1 FRmax). The parameter po, the peptizing power of maltenes, isdefined as the quantity FRmax(1/Cmin) + 1. The parameter P
24、,the overall compatibility of the system, is defined as po/(1 pa), or (1/Cmin+ 1).5. Significance and Use5.1 This test method is intended primarily as a laboratorydiagnostic tool for estimating the colloidal stability of bitumenasphalt, asphalt cross blends, aged asphalt, and heavy oilresiduum. Hist
25、orically, bituminous asphalt and heavy oil re-sidua have been modeled as colloidal suspensions in which apolar associated asphaltene moiety (the dispersed phase) issuspended in a maltene solvent moiety (the dispersing me-dium) (refer to Test Methods D3279, D4124, and D5546 forfurther definition of a
26、sphalt fraction materials). The extent towhich these two moieties remain in state of peptization is ameasure of the compatibility (colloidal stability) of the suspen-sion. Compatibility influences the physical properties of thesematerials, including rheological properties, for example, phaseangle an
27、d viscosity. This test method and other similar testmethods, along with the classical Heithaus test, measures theoverall compatibility of a colloidal system by determining aFIG. 1 Automated Titration ApparatusD6703 132parameter referred to as the state of peptization, P. The valueof P commonly varie
28、s between 2.5 to 10 for unmodified or neatasphalts. Materials calculated to have low values of P aredesignated incompatible. Materials calculated to have high Pvalues are designated compatible. Values in P are calculated asa function of two parameters that relate to the peptizability ofthe asphalten
29、e moiety (the asphaltene peptizability parameter,pa) and the solvent power of the maltene moiety (the maltenepeptizing power parameter, po). Values of paand poarecalculated as functions of the quantities Cminand FRmax. Valuesof Cminand FRmaxare determined from experimental variables,the weight of as
30、phalt (Wa), the volume of solvent (VS)todissolve the weight of asphalt, and the volume of titrant (VT)added to initiate flocculation.6. Apparatus6.1 UV-visible Spectrophotometer, wavelength scanningrange from 200 to 1000 nm, with adjustable aperture orattenuator.6.2 Digital Acquisition System (compu
31、ter).6.3 Water-Jacketed Reaction Vessel, 250-mL, two.6.4 TFE-fluorocarbon Covers, two.6.4.1 TFE-fluorocarbon Cover No. 1, (see Fig. 4), threadedto hold a 40 mL reaction vial. Three holes, 1.5 mm diameter,concentric to the covers center are tapped to set within theinside diameter of the vial when att
32、ached to the TFE-fluorocarbon cover,. One additional hole, 3.0 mm, is tapped offcenter, positioned just to the outside of where the reaction vialis positioned in the TFE-fluorocarbon cover. This hole allowsthe temperature probe to be inserted into the water-filledreaction vessel.6.4.2 TFE-fluorocarb
33、on Cover No. 2, as a lid for the second200-mL, water-jacketed reaction vessel, containing titrant.Dimensions: thickness, 2.0 mm; diameter, 70 mm. One hole1.5 mm in diameter tapped through the covers center. Thiscover is identical to the cover described in 6.4.1 except for thenumber of holes, and is
34、not threaded.FIG. 2 Onset of Flocculation Peaks Measured at Three Successively Increasing Concentrations (Solvent: Toluene, Titrant: Isooctane)FIG. 3 Flocculation Ratio Versus Dilution Concentration for One Stable Asphalt and One Less Stable AsphaltD6703 1336.5 High Flow Rate Metering PumpFlow rate
35、range from0.5 to 10.0 mL/min; flow rate consistency, 6 0.1 mL/min; andpiston chamber resistant to damage from solvent contact.6.6 Low Flow Rate Metering PumpFlow rate range from0.100 to 1.000 mL/min; flow rate consistency, 60.002 mL/min; and piston chamber resistant to damage from solventcontact.6.7
36、 Magnetic Stirring Plates, two.6.8 Refrigerated Water Bath CirculatorTemperaturevariation, 60.1C; temperature range from 0 to 100C.6.9 Quartz Flow Cell, 0.20 mm path length3with 6.35 mmflanged fittings.6.10 TFE-fluorocarbon Tubing, 0.559 mm inside diameter/1.575 mm outside diameter.6.11 Reaction Via
37、ls, 40 mL volume capacity.6.12 “4-hole” TFE-fluorocarbon cover and “1-hole” TFE-fluorocarbon cover.6.13 TFE-fluorocarbon-Coated Magnetic Stir Bars.6.14 Stopwatch.6.15 Syringe, 5.000 cc, glass, gas-sealed, and resistant tosolvents that it will be used to sample.6.16 TFE-fluorocarbon Tube Fittings (4)
38、, including stan-dard 6.35 mm flanged fittings for 0.559 mm inside diameter/1.575 mm outside diameter TFE-fluorocarbon tubing.6.17 Neoprene Tubing, 13 mm inside diameter.6.18 Tubing Clamps, sized to fit 13 mm inside diametertubing.6.19 Digital Probe Thermometer, C (calibrated to 60.2C).Probe length,
39、 80-mm, probe diameter, 3.0 mm.3The sole source of supply of the apparatus known to the committee at this timeis Starna Cells, Inc. If you are aware of alternative suppliers, please provide thisinformation to ASTM International Headquarters. Your comments will receivecareful consideration at a meeti
40、ng of the responsible technical committee,1whichyou may attend.FIG. 4 Reaction Vial (30 mL) with TFE-fluorocarbon Cover and Temperature ProbeD6703 1346.20 Graduated Cylinders, two. Volumes: 1.000 6 0.001mL and 10.0 6 0.1 mL.6.21 Argon Gas Supply.6.22 Laboratory JacksLaboratory jacks are used as stan
41、dsfor the metering pumps previously listed. The size require-ments of these laboratory jacks will vary depending on the sizeto the metering pumps.6.23 Beakers, two. Volume: 500 mL.6.24 Polypropylene Rinse Bottles, two. Volume: 200 mL.6.25 TFE-fluorocarbon Lined Caps, for 40 mL reactionvials.7. Reage
42、nts7.1 Purity of ReagentsHPLC grade chemicals shall beused in all sample preparations and tests. Unless otherwiseindicated, it is intended that all reagents conform to thespecifications of the Committee on Analytical Reagents of theAmerican Chemical Society where such specifications areavailable.4Ot
43、her grades may be used, provided it is firstascertained that the reagent is of sufficiently high purity topermit its use without lessening the accuracy of the determi-nation.7.2 Isooctane (2,2,4-trimethylpentane), HPLC grade.7.3 Toluene, HPLC grade.7.4 Toluene, reagent grade.8. Assembly8.1 Installat
44、ion Requirements:8.1.1 It is recommended that the following assembly beconducted in a fume hood. The fume hood should be ofsufficient size to accommodate all pieces of the apparatus andsupplies needed to perform the test method.8.1.2 The fume hood should be equipped with a pump orhouse vacuum line f
45、or the assembly of a vacuum trap, usedduring the procedural cleanup step (see 10.2.8).8.2 Assembly (Fig. 1):8.2.1 Circulation Loop AssemblyA sample (circulationloop) is assembled using a high flow rate metering pumpplumbed between a short path length flow cell and a TFE-fluorocarbon cover (fitted to
46、 a 40 mL reaction vial/200 mLwater-jacketed reaction vessel assembly) using 0.559 mminside diameter/1.575-mm outside diameter TFE-fluorocarbontubing fitted with standard 6.2 mm flange fittings adaptable to0.559 mm inside diameter/1.575 mm outside diameter tubing.8.2.1.1 Position one of the 200-mL, w
47、ater-jacketed reactionvessels on one of the stir plates, next to the cuvette cell housingof the UV-visible spectrophotometer.8.2.1.2 Position a 0.1-mm path length flow cell in the cellhousing of the spectrophotometer and secure it into place.8.2.1.3 Position the high flow rate metering pump on alabo
48、ratory jack next to the stir plate. Attach a 6.35 mm flangedfitting to one end of a 100 mm long piece of 0.559 mm insidediameter/1.575 mm outside diameter TFE-fluorocarbon tubingand attach the flanged fitting provided with the flow cell to theopposite end of this piece of tubing. Fasten the tubing b
49、etweenthe inflow end of the flow cell and the outflow end of the highflow rate metering pump.8.2.1.4 Attach a second flanged fitting provided with theflow cell to one end of a second 300 mm long piece of 0.559mm inside diameter/1.575 mm outside diameter TFE-fluorocarbon tubing, leaving the other tubing end free. Fastenthe flanged fitting end of this tubing to the outflow end of theflow cell.8.2.1.5 Attach a 6.35 mm flanged fitting to a third 200 mmlong piece of 0.559 mm inside diameter/1.575 mm outsidediameter TFE-fluorocarbon tubing, leaving the
