# ASTM D2493D2493M-16

Designation: D2493/D2493M − 16Standard Practice forViscosity-Temperature Chart for Asphalt Binders1This standard is issued under the fixed designation D2493/D2493M; the number immediately following the designation indicates theyear of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of lastreapproval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.1. Scope1.1 The viscosity-temperature chart covered by this stan-dard is a convenient means of plotting data for estimating theviscosity of asphalt binders at any temperature within a limitedrange. Conversely, the chart may be used to ascertain thetemperature at which a desired viscosity is attained.1.2 The chart is suitable for asphalt binders and for asphaltsrecovered from laboratory aging tests or extracted from pave-ments.1.3 The chart is based on a viscosity-temperature relation-ship that can be plotted using any appropriate set of units. Forconvenience, charts based on both conventional and SI unitsare provided.1.4 The range of the chart is sufficient for roofing asphalts.1.5 The range of the chart is sufficient for asphalt binderswhose viscosity exceeds 0.01 Pa.S (10 centipoise).1.6 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard. The values stated ineach system may not be exact equivalents; therefore, eachsystem shall be used independently of the other. Combiningvalues from the two systems may result in nonconformancewith the standard.2. Referenced Documents2.1 ASTM Standards:2D341 Practice for Viscosity-Temperature Charts for LiquidPetroleum ProductsD2170 Test Method for Kinematic Viscosity of Asphalts(Bitumens)D2171 Test Method for Viscosity of Asphalts by VacuumCapillary ViscometerD4402 Test Method for Viscosity Determination of Asphaltat Elevated Temperatures Using a Rotational ViscometerD4957 Test Method forApparent Viscosity ofAsphalt Emul-sion Residues and Non-Newtonian Bitumens by VacuumCapillary ViscometerD7175 Test Method for Determining the Rheological Prop-erties of Asphalt Binder Using a Dynamic Shear Rheom-eter3. Significance and Use3.1 The viscosity-temperature chart is a convenient meansof plotting the viscosity data for estimating the viscosity ofasphalt binders, recovered asphalts, and roofing asphalts at anytemperature within a limited range. It is also a convenientmeans to estimate the temperature at which a desired viscosityis attained. Charts may be constructed manually or usingcomputer graphing software.3.2 Kinematic viscosity-temperature charts are described inPractice D341.4. Description4.1 Fig. 1 shows an example viscosity-temperature chart.For Fig. 1, the chart coordinates are logarithm of the logarithmof the viscosity in centipoise as the ordinate, and logarithm ofthe absolute temperature in degrees Rankine (degrees F +459.7) as the abscissa. However, the viscosity in poise and thetemperature in degrees Fahrenheit are shown in the chart forconvenience.4.2 Fig. 2 shows an example viscosity-temperature chart.For Fig. 2, the chart coordinates are logarithm of the logarithmof the viscosity in mPa·S as the ordinate, and logarithm of theabsolute temperature in degrees Kelvin (degrees C + 273.2) asthe abscissa. However, viscosity in Pa·S and the temperature indegrees Celsius are shown in the chart for convenience.4.3 The temperature range of the charts may be extended orabbreviated as necessary.5. Procedure5.1 If the viscosities are not known they should be deter-mined in accordance with Test Methods D2170, D2171,D4402, D4957,orD7175. Viscosities determined at tempera-tures other than the temperatures specified in each of these testmethods may be used.1This practice is under the jurisdiction of ASTM Committee D04 on Road andPaving Materials and is the direct responsibility of Subcommittee D04.44 onRheological Tests.Current edition approved Dec. 1, 2016. Published January 2017. Originallyapproved in 1966. Last previous edition approved in 2009 as D2493/D2493M – 09.DOI: 10.1520/D2493_D2493M-16.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at service@astm.org. For Annual Book of ASTMStandards volume information, refer to the standard’s Document Summary page onthe ASTM website.Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States15.2 For temperatures above 60 °C [140 °F], plot twoviscosity-temperature points and carefully draw a straight linethrough the points. Plot at least three viscosity-temperaturepoints if the included temperature range is below 60 °C[140 °F]. Carefully draw a straight line or curve through thepoints.Apoint on this line, within the temperature range of thepoints plotted, shows the viscosity at the corresponding desiredtemperature.NOTE 1—These charts are appropriate for use at higher temperatures,where asphalts are primarily viscous. At lower temperatures most asphaltbinders become viscoelastic. When this occurs, viscosity alone is insuf-ficient to describe an asphalt binder’s flow properties. Caution should beused when applying this standard below that temperature.NOTE 2—Some asphalt binders have viscosity-temperature relation-ships too complex to be represented by only three points, as shown in Fig.1. In this case, determine the viscosity at sufficient temperatures toproduce a curve adequate for the purpose intended.NOTE 3—Viscosities determined by extrapolation of data may beunreliable.5.3 The viscosity values represented by the data points mayhave been obtained at different shear rates. This chart does notreflect the shear rate at which the viscosities were determined.6. Keywords6.1 asphalt; rheology; viscosity; viscosity-temperature chartFIG. 1 Viscosity-Temperature Chart for Asphalt Binders on Which a Typical Experimental Curve Has Been PlottedD2493/D2493M − 162APPENDIX(Nonmandatory Information)X1. SUGGESTIONS FOR DATA ANALYSISX1.1 The chart in Fig. 1 includes the region where theviscosity of asphalt binders depends not only on thetemperature, but also on the shearing conditions. Therefore, thedata plotted on the viscosity-temperature chart must be ob-tained under standardized shearing conditions, for example, atthe same shear rate, or the same shear stress. Constant shearingconditions also imply the use of the same viscometer, orviscometers of the same type and size, to avoid differences inviscosity values caused by differences in the extent of break-down of the micellar structure of the asphalt due to shearing inthe measurement process.X1.2 Viscosities of asphalt binders are often reported at anarbitrary shear rate of 0.05 s−1. Interpolation or extrapolation ofmeasured viscosity data is often required to obtain values forthis shear rate. A useful model for interpolating or extrapolat-ing asphalt rheological measurements is the empirical “PowerLaw” relationship:τ 5 η1γ˙c(X1.1)where:τ = the shearing stress,γ˙ = the rate of shear,η1= the apparent viscosity at a shear rate of 1 s−1, andc = the slope of a plot of log τ versus log γ˙.The parameter c is called the complex flow index, and is anindicator of the rheological character of the material. ForNewtonian liquids, whose viscosities do not vary with shearrate, c =1. If c 1, the apparent viscosityincreases with shear rate.FIG. 2 Viscosity-Temperature Chart for Asphalt Binders on Which a Typical Experimental Curve Has Been PlottedD2493/D2493M − 163X1.3 Because a small error in the value of c can cause alarge error in an extrapolated viscosity value, it is recom-mended that the Power Law slope be determined usingreplicate tests on the material. The average value of c can bedetermined by regression analysis of the log τ versus log γ˙ data.If the data for replicate tests do not superimpose on a plot of allthe data on the same chart, the calibration and operatingprocedure for the viscometer should be checked before pro-ceeding further with the data analysis. If there are a smallnumber of outliers, these can be discarded, and the remainderof the data used in the regression analysis. Fig. X1.1 shows anexample of data containing outliers that should be ignored.X1.3.1 The objective of screening for outliers should be toretain all data that legitimately belong in the population ofresults characteristic of the test method used, and to eliminateonly those that differ so drastically that their inclusion distortsthe shear stress versus shear rate relationship. Therefore, thecriterion for rejecting data should be conservative. If a statis-tical technique is used, the significance level of the test shouldbe no greater than one percent.X1.4 Large extrapolations of rheological data to obtainvalues at constant shear rate are often unavoidable becausemost viscometers allow a limited range of shear stress, and thelarge variation in viscosity over a range of temperatures resultsin large differences in observed shear rate at different testtemperatures. A procedure which circumvents this problem isto plot the apparent viscosity at constant power input per unitvolume as a function of temperature. This avoids long extrapo-lations of the shear stress/shear rate relationships. H. E.Schweyer and others have recommended that apparent viscosi-ties at a constant power input of 100 W/m3be used. However,this value has no theoretical significance, and may not beappropriate for all viscometers. A value which minimizes theamount of extrapolation needed to estimate the apparentviscosities in the temperature range of interest should beselected.X1.5 To estimate the apparent viscosity at constant powerinput, first determine the Power Law constants η1and c from aplot or regression analysis of log shear stress versus log shearrate. Calculate the apparent viscosity at power input P from:ηP5 η1FPη1Gc21c11(X1.2)where:ηP= apparent viscosity, Pa.s at power input P, W/m3,η1= apparent viscosity, Pa.s at 1 s−1shear rate, andc = complex flow index.X1.6 The effect of temperature on apparent viscosity can beshown by plotting the constant power input viscosities at twoor more temperatures on the chart in Fig. 1. Because of thenonlinearity of the scales on this chart, the viscosities must beplotted in the units shown. Many asphalts will have a straightline viscosity versus temperature relationship on the chart.However, a minimum of three points should be plotted, toensure that the nature of the relationship is shown. Because ofthe possibility of curvature, particularly at very high viscositylevels, extrapolation is not recommended.X1.7 Alternatively, a regression analysis of log log η versuslog T (absolute temperature) can be performed. To be consis-tent with Fig. 1, the viscosity values must be converted tomPa.s or cP before taking the logarithms. A straight regressionline of this type is shown in Fig. X1.2.FIG. X1.1 Power Law Shear Stress versus Shear Rate Relation-shipFIG. X1.2 Viscosity versus Temperature RelationshipD2493/D2493M − 164ASTM 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 determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. 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