ASTM D7552-09(2014)

Standard Test Method for Determining the Complex Shear Modulus (G*) Of Bituminous Mixtures Using Dynamic Shear Rheometer

SIGNIFICANCE AND USE
5.1 The complex shear modulus of bituminous mixtures is a fundamental property of the material. Test results at critical temperatures (Tcritical) are used for specifications for some mixes. Mixtures with stiffer binders, aged mixtures, mixtures with higher amounts of fines (material finer than 75µ), and mixtures with lower voids all tend to have higher complex shear modulus values than mixtures with less stiff binders, unaged mixes, mixtures with low levels of fines and higher air voids. In general, mixtures with higher complex shear modulus values at a given service temperature will exhibit lower permanent deformation values than similar mixtures tested at the same temperature that have lower complex shear modulus values.  
Note 2: The quality of the results produced by this standard are dependent on the competence of the personnel performing the procedure and the capability, calibration, and maintenance of the equipment used. Agencies that meet the criteria of Practice D3666 are generally considered capable of competent and objective testing/sampling/inspection/etc. Users of this standard are cautioned that compliance with Practice D3666 alone does not completely assure reliable results. Reliable results depend on many factors; following the suggestions of Practice D3666 or some similar acceptable guideline provides a means of evaluating and controlling some of those factors.
SCOPE
1.1 This test method covers the determination of the complex shear modulus of bituminous mixtures using torsion rectangular geometry on a dynamic shear rheometer (DSR). It is applicable to bituminous mixtures having complex shear modulus values greater than 1 × 104 Pa when tested over a range of temperatures from 10°C to 76°C at frequencies of 0.01 to 25 Hz and strains of 0.001 % to 0.1 %. The determination of complex shear modulus is typically determined at 20°C to 70°C at 0.01% strain at 10 discrete frequency values covering 0.01 to 10 Hz. From these data, temperature or frequency master curves can be generated as required. This test method is intended for determining the complex shear modulus of bituminous mixtures as required for specification testing or quality control of bituminous mixture production.  
1.2 This test method is appropriate for laboratory prepared and compacted mixtures, field produced and laboratory compacted mixtures or field cores, regardless of binder type or grade and regardless of whether RAP is used in the mixture. Due to the geometry of the specimens being tested this test method is not applicable to open-graded or SMA mixtures. It has been found to be appropriate for dense-graded mixtures, whether coarse- or fine-graded, with 19 mm or smaller nominal maximum aggregate size.  
1.3 The between-laboratory reproducibility of this test method is being determined and will be available on or before June 2012. Therefore, this test method should not be used for acceptance or rejection of materials for purchasing purposes.  
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.5 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.

General Information

• Status: Historical
• Publication Date: 31-Jul-2014
• ICS: 75.140 - Waxes, bituminous materials and other petroleum products
• ICS: 91.100.50 - Binders. Sealing materials
• Technical Committee: D04 - Road and Paving Materials
• Drafting Committee: D04.26 - Fundamental/Mechanistic Tests

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D7552 − 09 (Reapproved 2014)
Standard Test Method for
Determining the Complex Shear Modulus (G*) Of
Bituminous Mixtures Using Dynamic Shear Rheometer
This standard is issued under the fixed designation D7552; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, 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 priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
1.1 This test method covers the determination of the com-
plex shear modulus of bituminous mixtures using torsion
2. Referenced Documents
rectangular geometry on a dynamic shear rheometer (DSR). It
is applicable to bituminous mixtures having complex shear 2.1 ASTM Standards:
modulus values greater than1×10 Pa when tested over a C670Practice for Preparing Precision and Bias Statements
rangeoftemperaturesfrom10°Cto76°Catfrequenciesof0.01 for Test Methods for Construction Materials
to25Hzandstrainsof0.001%to0.1%.Thedeterminationof D140Practice for Sampling Bituminous Materials
complex shear modulus is typically determined at 20°C to D2041Test Method for Theoretical Maximum Specific
70°C at 0.01% strain at 10 discrete frequency values covering Gravity and Density of Bituminous Paving Mixtures
0.01 to 10 Hz. From these data, temperature or frequency D2726Test Method for Bulk Specific Gravity and Density
mastercurvescanbegeneratedasrequired.Thistestmethodis of Non-Absorptive Compacted Bituminous Mixtures
intended for determining the complex shear modulus of bitu- D3203Test Method for Percent Air Voids in Compacted
minous mixtures as required for specification testing or quality Dense and Open Bituminous Paving Mixtures
control of bituminous mixture production. D3666Specification for Minimum Requirements for Agen-
cies Testing and Inspecting Road and Paving Materials
1.2 This test method is appropriate for laboratory prepared
D6752Test Method for Bulk Specific Gravity and Density
and compacted mixtures, field produced and laboratory com-
of Compacted Bituminous Mixtures Using Automatic
pacted mixtures or field cores, regardless of binder type or
Vacuum Sealing Method
grade and regardless of whether RAP is used in the mixture.
D6857Test Method for Maximum Specific Gravity and
Due to the geometry of the specimens being tested this test
Density of Bituminous Paving Mixtures UsingAutomatic
method is not applicable to open-graded or SMA mixtures. It
Vacuum Sealing Method
has been found to be appropriate for dense-graded mixtures,
D6925Test Method for Preparation and Determination of
whethercoarse-orfine-graded,with19mmorsmallernominal
the Relative Density ofAsphalt Mix Specimens by Means
maximum aggregate size.
of the Superpave Gyratory Compactor
1.3 The between-laboratory reproducibility of this test
D6926Practice for Preparation of Bituminous Specimens
method is being determined and will be available on or before
Using Marshall Apparatus
June 2012. Therefore, this test method should not be used for
D7175Test Method for Determining the Rheological Prop-
acceptance or rejection of materials for purchasing purposes.
erties of Asphalt Binder Using a Dynamic Shear Rheom-
1.4 The values stated in SI units are to be regarded as eter
D7312Test Method for Determining the Permanent Shear
standard. No other units of measurement are included in this
standard. Strain and Complex Shear Modulus of Asphalt Mixtures
Using the Superpave Shear Tester (SST)
1.5 This standard does not purport to address all of the
E77Test Method for Inspection and Verification of Ther-
safety concerns, if any, associated with its use. It is the
mometers
responsibility of the user of this standard to establish appro-
E563Practice for Preparation and Use of an Ice-Point Bath
as a Reference Temperature
This test method is under the jurisdiction of ASTM Committee D04 on Road
and Paving Materials and is the direct responsibility of Subcommittee D04.26 on
Fundamental/Mechanistic Tests. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Aug. 1, 2014. Published November 2014. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 2009. Last previous edition approved in 2009 as D7552–09. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/D7552-09R14. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7552 − 09 (2014)
E644Test Methods for Testing Industrial Resistance Ther- 3.1.11 verification, n—aprocessthatestablisheswhetherthe
mometers results of a previously calibrated measurement instrument,
measurement system, or material measure are stable. Usually
2.2 Other Standards:
performed internally within the operating laboratory.
DIN Standard 43760Standard for Calibration of Platinum
Resistance Thermometers
4. Summary of Test Method
4.1 This standard contains the procedure used to measure
3. Terminology
the complex shear modulus of a bituminous mixture using a
3.1 Definitions of Terms Specific to This Standard:
DSR in oscillatory mode and using torsional rectangular
3.1.1 asphalt binder, n—an asphalt-based cement that is
geometry. The DSR must be temperature-controlled using a
produced from petroleum residue either with or without the
forced air system.
addition of non-particulate modifiers.
4.2 The standard is suitable for use when the complex shear
3.1.2 calibration, n—a process that establishes the relation-
modulus is greater than1×10 Pa at the test temperature.The
ship (traceability) between the results of a measurement
complex shear modulus is typically determined at 20°C to
instrument, measurement system, or material measure and the
70°C, although other test temperatures may be used.
corresponding values assigned to a reference standard. Cali-
4.3 Test specimens, nominally 49 6 2 mm in length, 12 6
bration is typically performed by the manufacturer or an
2 mm in width and 9 6 1.5 mm in thickness may be cut from
external commercial calibration service.
gyratory or Marshall laboratory specimens or from field cores
3.1.3 complex shear modulus (G*), n—a complex number
(see Figs. 1-3). Specimens can be obtained from bituminous
that is defined by the ratio of shear stress to shear strain.
mixture samples compacted using other devices as long as it is
3.1.4 dummy test specimen, n—a rectangular prismatic or
possibletodeterminetheairvoidsofthemixturesamples.The
cylindrical specimen of bituminous mix prepared as discussed
test specimens are mounted with the 49 6 2 mm length
inSection9.2,intowhichasmallholeisdrilledandintowhich
forming a vertical dimension in the DSR.
a PRT wire is inserted. The dummy specimen is then mounted
4.4 During testing, one of the fixtures is rotated with
inthetorsionfixtureoftheDSRforthepurposeofdetermining
respect to the other at a pre-selected % strain and a range of
the temperature in the bituminous mixture. In addition the
frequencies at the selected temperatures. The test shall be
dummy specimen can be used to ascertain the amount of time
conducted at 0.01% strain unless otherwise stated. The %
needed to bring a test specimen to the appropriate test
strain stipulated in this test method has been found to produce
temperature.
acceptable results for the bituminous materials investigated to
3.1.4.1 Discussion—The dummy test specimen is not used
date.
to measure the modulus characteristics of the bituminous
mixture but is used to determine temperature corrections and
NOTE 1—Different strain values, within the capabilities of individual
equilibrium times. equipment, may be selected for testing materials beyond the scope of
those tested to date. Regardless of % strain or test temperatures chosen or
3.1.5 loading cycle, n—refers to the application of sinusoi-
test materials investigated, the basic testing process described herein will
dal stress or strain loading for a specified duration.
not change.
3.1.6 shear stress, n—the force per unit area that produces
4.5 The test specimen is maintained at the test temperature
the flow.
60.1°C by enclosing the upper and lower fixtures in a
thermally controlled environmental test chamber.
3.1.7 portable thermometer, n—refers to an electronic de-
vicethatisseparatefromthedynamicshearrheometerandthat
5. Significance and Use
consists of a detector (probe containing a thermocouple or
5.1 Thecomplexshearmodulusofbituminousmixturesisa
resistive element), associated electronic circuitry, and readout
fundamental property of the material. Test results at critical
system.
temperatures (T ) are used for specifications for some
critical
3.1.8 reference thermometer, n—refers to a NIST-traceable
mixes. Mixtures with stiffer binders, aged mixtures, mixtures
liquid-in-glass or electronic thermometer that is used as a
with higher amounts of fines (material finer than 75µ), and
laboratory standard.
mixtures with lower voids all tend to have higher complex
3.1.9 temperature correction, n—difference in temperature
shear modulus values than mixtures with less stiff binders,
between the temperature indicated by the DSR and the test
unaged mixes, mixtures with low levels of fines and higher air
specimen as measured by the portable thermometer inserted
voids.Ingeneral,mixtureswithhighercomplexshearmodulus
between the test plates.
values at a given service temperature will exhibit lower
3.1.10 thermal equilibrium, n—condition where the tem-
permanent deformation values than similar mixtures tested at
perature of the test specimen mounted between the test plates
the same temperature that have lower complex shear modulus
is constant with time.
values.
Depending upon whether a stress or strain controlled rheometer is being used,
Available from Beuth Verlag GmbH (DIN-- DIN Deutsches Institut fur either the upper or lower fixture will be the one which is rotated. This test method
Normunge.V.),Burggrafenstrasse6,10787,Berlin,Germany,http://www.en.din.de. is applicable to both stress and strain controlled rheometers. When a stress
controlled rheometer is used, the test is performed in strain controlled mode.
D7552 − 09 (2014)
FIG. 1 Schematic of Preparing Torsion Rectangular Specimens
NOTE 2—The quality of the results produced by this standard are
test specimen is mounted in the fixture, the length of specimen
dependent on the competence of the personnel performing the procedure
betweenthetwomountingpointsisthelengthofthespecimen.
and the capability, calibration, and maintenance of the equipment used.
Thewidthandthicknessofthespecimenisdeterminedpriorto
AgenciesthatmeetthecriteriaofPracticeD3666aregenerallyconsidered
mounting the specimen in the DSR using a digital caliper and
capableofcompetentandobjectivetesting/sampling/inspection/etc.Users
of this standard are cautioned that compliance with Practice D3666 alone
is reported to the nearest 0.01 mm. These values are entered
does not completely assure reliable results. Reliable results depend on
into the software of the instrument where the test specimen
many factors; following the suggestions of Practice D3666 or some
dimensionsarerequested.Duetothepotentialforvariabilityin
similar acceptable guideline provides a means of evaluating and control-
the width and thickness due to the sample preparation
ling some of those factors.
procedure, the width and thickness is determined in the central
6. Interferences
portion of the test specimen.
6.1 Due to the nature of test geometry this test cannot be
used to determine the complex shear modulus of rectangular
7. Apparatus
specimens obtained from SMA (Stone Mastic or Matrix
7.1 The apparatus for performing the test as described in
Asphalt) or OGFC (Open Graded Friction Course) mixtures.
this method shall be the equipment described in Test Method
Without confining pressure these specimens fall apart when
D7175 under the section heading of Apparatus except as
brought to test temperature. At this point in time there is no
amended below.
suitable method for imparting confining pressure on the test
specimens.
7.2 Test Fixtures—Two fixtures capable of securing the
6.1.1 The calculation of the complex shear modulus from
rectangular test specimens with the long dimension of the test
the data obtained from the DSR is highly dependent upon an
article in a vertical plane are required.
accurate measurement of the dimensions of the test specimen.
7.3 A torque wrench capable of applying a torque load of
In the procedure, the length of the test specimen is the gap
0.25 N·m (250 mN·m) 6 0.05 N·m of torque to tighten the test
distance between the mounting fixtures after the zero gap
measurement of the torsion fixture has been made. Once the specimen in the mounting fixture without crushing.
D7552 − 09 (2014)
FIG. 2 Sample Preparation to Obtain 50-mm Wide by 12-mm Thick Rectangular Specimen
FIG. 3 Sample Preparation to Obtain 50-mm Wide by 12-mm Wide by 10-mm Thick Specimen.
7.4 Environmental Chamber—A chamber for controlling used in a forced air environmental chamber, a suitable dryer
the temperature of the test specimens. The medium used to must be included to prevent condensation of moisture on the
control the chamber shall be compressed laboratory air or testspecimen.Theenvironmentalchamberandthetemperature
commerciallybottledair.Chilled,compressedlaboratoryairor controller shall control the temperature of the test specimen
liquid nitrogen (LN2) is required if testing temperatures below mounted between the grips, including any thermal gradients
approximately 30°C is to be conducted.When laboratory air is within the test specimen, at the test temperature 6 0.1°C. Due
D7552 − 09 (2014)
to the geometry and type of material being tested, water baths 8.2.2 Acetone or ethanol may be used as needed for
and Peltier fixtures cannot be used to control the test tempera- removing solvent residue from the surfaces of the mounting
ture of the specimens. Some companies manufacture a Peltier clamps.
heated submersion cell, which uses water or some other liquid
8.3 Reference Thermometer—Either a NIST-traceable
medium to condition the test specimen. Testing the mixture
liquid-in-glass thermometer(s) (Section 8.3.1) or NIST-
while submerged could introduce errors in the results due to
traceable digital electronic thermometer (Section 8.3.2) shall
weakening of the mix due to moisture interaction.
bemaintainedinthelaboratoryasatemperaturestandard.This
7.5 Temperatur
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM 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 accurately, 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.
Designation: D7552 − 09 D7552 − 09 (Reapproved 2014)
Standard Test Method for
Determining the Complex Shear Modulus (G*) Of
Bituminous Mixtures Using Dynamic Shear Rheometer
This standard is issued under the fixed designation D7552; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number 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 test method covers the determination of the complex shear modulus of bituminous mixtures using torsion rectangular
geometry on a dynamic shear rheometer (DSR). It is applicable to bituminous mixtures having complex shear modulus values
greater than 1 × 10 Pa when tested over a range of temperatures from 10°C to 76°C at frequencies of 0.01 to 25 Hz and strains
of 0.001 % to 0.1 %. The determination of complex shear modulus is typically determined at 20°C to 70°C at 0.01% strain at 10
discrete frequency values covering 0.01 to 10 Hz. From these data, temperature or frequency master curves can be generated as
required. This test method is intended for determining the complex shear modulus of bituminous mixtures as required for
specification testing or quality control of bituminous mixture production.
1.2 This test method is appropriate for laboratory prepared and compacted mixtures, field produced and laboratory compacted
mixtures or field cores, regardless of binder type or grade and regardless of whether RAP is used in the mixture. Due to the
geometry of the specimens being tested this test method is not applicable to open-graded or SMA mixtures. It has been found to
be appropriate for dense-graded mixtures, whether coarse- or fine-graded, with 19 mm or smaller nominal maximum aggregate
size.
1.3 The between-laboratory reproducibility of this test method is being determined and will be available on or before June 2012.
Therefore, this test method should not be used for acceptance or rejection of materials for purchasing purposes.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.5 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. Referenced Documents
2.1 ASTM Standards:
C670 Practice for Preparing Precision and Bias Statements for Test Methods for Construction Materials
D140 Practice for Sampling Bituminous Materials
D2041 Test Method for Theoretical Maximum Specific Gravity and Density of Bituminous Paving Mixtures
D2726 Test Method for Bulk Specific Gravity and Density of Non-Absorptive Compacted Bituminous Mixtures
D3203 Test Method for Percent Air Voids in Compacted Dense and Open Bituminous Paving Mixtures
D3666 Specification for Minimum Requirements for Agencies Testing and Inspecting Road and Paving Materials
D6752 Test Method for Bulk Specific Gravity and Density of Compacted Bituminous Mixtures Using Automatic Vacuum
Sealing Method
D6857 Test Method for Maximum Specific Gravity and Density of Bituminous Paving Mixtures Using Automatic Vacuum
Sealing Method
D6925 Test Method for Preparation and Determination of the Relative Density of Hot Mix Asphalt (HMA) Specimens by Means
of the Superpave Gyratory Compactor
D6926 Practice for Preparation of Bituminous Specimens Using Marshall Apparatus
This test method is under the jurisdiction of ASTM Committee D04 on Road and Paving Materials and is the direct responsibility of Subcommittee D04.26 on
Fundamental/Mechanistic Tests.
Current edition approved July 1, 2009Aug. 1, 2014. Published August 2009November 2014. Originally approved in 2009. Last previous edition approved in 2009 as
D7552 – 09. DOI: 10.1520/D7552-09.10.1520/D7552-09R14.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7552 − 09 (2014)
D7175 Test Method for Determining the Rheological Properties of Asphalt Binder Using a Dynamic Shear Rheometer
D7312 Test Method for Determining the Permanent Shear Strain and Complex Shear Modulus of Asphalt Mixtures Using the
Superpave Shear Tester (SST)
E77 Test Method for Inspection and Verification of Thermometers
E563 Practice for Preparation and Use of an Ice-Point Bath as a Reference Temperature
E644 Test Methods for Testing Industrial Resistance Thermometers
2.2 Other Standards:
DIN Standard 43760 Standard for Calibration of Platinum Resistance Thermometers
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 asphalt binder, n—an asphalt-based cement that is produced from petroleum residue either with or without the addition
of non-particulate modifiers.
3.1.2 calibration, n—a process that establishes the relationship (traceability) between the results of a measurement instrument,
measurement system, or material measure and the corresponding values assigned to a reference standard. Calibration is typically
performed by the manufacturer or an external commercial calibration service.
3.1.3 complex shear modulus (G*), n—a complex number that is defined by the ratio of shear stress to shear strain.
3.1.4 dummy test specimen, n—a rectangular prismatic or cylindrical specimen of bituminous mix prepared as discussed in
Section 9.2, into which a small hole is drilled and into which a PRT wire is inserted. The dummy specimen is then mounted in
the torsion fixture of the DSR for the purpose of determining the temperature in the bituminous mixture. In addition the dummy
specimen can be used to ascertain the amount of time needed to bring a test specimen to the appropriate test temperature.
Available from Beuth Verlag GmbH (DIN-- DIN Deutsches Institut fur Normung e.V.), Burggrafenstrasse 6, 10787, Berlin, Germany, http://www.en.din.de.
3.1.4.1 Discussion—
The dummy test specimen is not used to measure the modulus characteristics of the bituminous mixture but is used to determine
temperature corrections and equilibrium times.
3.1.5 loading cycle, n—refers to the application of sinusoidal stress or strain loading for a specified duration.
3.1.6 shear stress, n—the force per unit area that produces the flow.
3.1.7 portable thermometer, n—refers to an electronic device that is separate from the dynamic shear rheometer and that consists
of a detector (probe containing a thermocouple or resistive element), associated electronic circuitry, and readout system.
3.1.8 reference thermometer, n—refers to a NIST-traceable liquid-in-glass or electronic thermometer that is used as a laboratory
standard.
3.1.9 temperature correction, n—difference in temperature between the temperature indicated by the DSR and the test specimen
as measured by the portable thermometer inserted between the test plates.
3.1.10 thermal equilibrium, n—condition where the temperature of the test specimen mounted between the test plates is constant
with time.
3.1.11 verification, n—a process that establishes whether the results of a previously calibrated measurement instrument,
measurement system, or material measure are stable. Usually performed internally within the operating laboratory.
4. Summary of Test Method
4.1 This standard contains the procedure used to measure the complex shear modulus of a bituminous mixture using a DSR in
oscillatory mode and using torsional rectangular geometry. The DSR must be temperature-controlled using a forced air system.
4.2 The standard is suitable for use when the complex shear modulus is greater than 1 × 10 Pa at the test temperature. The
complex shear modulus is typically determined at 20°C to 70°C, although other test temperatures may be used.
4.3 Test specimens, nominally 49 6 2 mm in length, 12 6 2 mm in width and 9 6 1.5 mm in thickness may be cut from gyratory
or Marshall laboratory specimens or from field cores (see Figs. 1-3). Specimens can be obtained from bituminous mixture samples
compacted using other devices as long as it is possible to determine the air voids of the mixture samples. The test specimens are
mounted with the 49 6 2 mm length forming a vertical dimension in the DSR.
D7552 − 09 (2014)
FIG. 1 Schematic of Preparing Torsion Rectangular Specimens
FIG. 2 Sample Preparation to Obtain 50-mm Wide by 12-mm Thick Rectangular Specimen
D7552 − 09 (2014)
FIG. 3 Sample Preparation to Obtain 50-mm Wide by 12-mm Wide by 10-mm Thick Specimen.
4.4 During testing, one of the fixtures is rotated with respect to the other at a pre-selected % strain and a range of frequencies
at the selected temperatures. The test shall be conducted at 0.01 % strain unless otherwise stated. The % strain stipulated in this
test method has been found to produce acceptable results for the bituminous materials investigated to date.
NOTE 1—Different strain values, within the capabilities of individual equipment, may be selected for testing materials beyond the scope of those tested
to date. Regardless of % strain or test temperatures chosen or test materials investigated, the basic testing process described herein will not change.
4.5 The test specimen is maintained at the test temperature 60.1°C by enclosing the upper and lower fixtures in a thermally
controlled environmental test chamber.
5. Significance and Use
5.1 The complex shear modulus of bituminous mixtures is a fundamental property of the material. Test results at critical
temperatures (T ) are used for specifications for some mixes. Mixtures with stiffer binders, aged mixtures, mixtures with
critical
higher amounts of fines (material finer than 75μ), and mixtures with lower voids all tend to have higher complex shear modulus
values than mixtures with less stiff binders, unaged mixes, mixtures with low levels of fines and higher air voids. In general,
mixtures with higher complex shear modulus values at a given service temperature will exhibit lower permanent deformation
values than similar mixtures tested at the same temperature that have lower complex shear modulus values.
NOTE 2—The quality of the results produced by this standard are dependent on the competence of the personnel performing the procedure and the
capability, calibration, and maintenance of the equipment used. Agencies that meet the criteria of Standard Practice D3666 are generally considered
capable of competent and objective testing/sampling/inspection/etc. Users of this standard are cautioned that compliance with Practice D3666 alone does
not completely assure reliable results. Reliable results depend on many factors; following the suggestions of Practice D3666 or some similar acceptable
guideline provides a means of evaluating and controlling some of those factors.
6. Interferences
6.1 Due to the nature of test geometry this test cannot be used to determine the complex shear modulus of rectangular specimens
obtained from SMA (Stone Mastic or Matrix Asphalt) or OGFC (Open Graded Friction Course) mixtures. Without confining
pressure these specimens fall apart when brought to test temperature. At this point in time there is no suitable method for imparting
confining pressure on the test specimens.
Depending upon whether a stress or strain controlled rheometer is being used, either the upper or lower fixture will be the one which is rotated. This test method is
applicable to both stress and strain controlled rheometers. When a stress controlled rheometer is used, the test is performed in strain controlled mode.
D7552 − 09 (2014)
6.1.1 The calculation of the complex shear modulus from the data obtained from the DSR is highly dependent upon an accurate
measurement of the dimensions of the test specimen. In the procedure, the length of the test specimen is the gap distance between
the mounting fixtures after the zero gap measurement of the torsion fixture has been made. Once the test specimen is mounted in
the fixture, the length of specimen between the two mounting points is the length of the specimen. The width and thickness of the
specimen is determined prior to mounting the specimen in the DSR using a digital caliper and is reported to the nearest 0.01 mm.
These values are entered into the software of the instrument where the test specimen dimensions are requested. Due to the potential
for variability in the width and thickness due to the sample preparation procedure, the width and thickness is determined in the
central portion of the test specimen.
7. Apparatus
7.1 The apparatus for performing the test as described in this method shall be the equipment described in Test Method D7175
under the section heading of Apparatus except as amended below.
7.2 Test Fixtures—Two fixtures capable of securing the rectangular test specimens with the long dimension of the test article
in a vertical plane are required.
7.3 A torque wrench capable of applying a torque load of 0.25 N·m (250 mN·m) 6 0.05 N·m of torque to tighten the test
specimen in the mounting fixture without crushing.
7.4 Environmental Chamber—A chamber for controlling the temperature of the test specimens. The medium used to control the
chamber shall be compressed laboratory air or commercially bottled air. Chilled, compressed laboratory air or liquid nitrogen
(LN2) is required if testing temperatures below approximately 30°C is to be conducted. When laboratory air is used in a forced
air environmental chamber, a suitable dryer must be included to prevent condensation of moisture on the test specimen. The
environmental chamber and the temperature controller shall control the temperature of the test specimen mounted between the
grips, including any thermal gradients within the test specimen, at the test temperature 6 0.1°C. Due to the geometry and type of
material being tested, water baths and Peltier fixtures cannot be used to control the test temperature of the specimens. Some
companies manufacture a Peltier heated submersion cell, which uses water or some other liquid medium
...