ASTM D7312-07
(Test Method)Standard Test Method for Determining the Permanent Shear Strain and Complex Shear Modulus of Asphalt Mixtures Using the Superpave Shear Tester (SST)
Standard Test Method for Determining the Permanent Shear Strain and Complex Shear Modulus of Asphalt Mixtures Using the Superpave Shear Tester (SST)
SIGNIFICANCE AND USE
The test procedures and associated analysis techniques described in this method can be used to determine complex shear modulus and permanent shear strain of asphalt mixtures. The shear frequency sweep test at constant height can be used to determine the complex shear modulus of a mixture. The repeated shear test at constant height can be used to determine permanent shear strain under repeated loading.
Note 4—The complex shear modulus is used to characterize the shear behavior of the mixture, and the permanent shear strain relates to pavement rutting.
SCOPE
1.1 This standard provides performance-related test procedures for the determination of stiffness complex shear modulus and permanent shear strain of asphalt mixtures using the Superpave Shear Tester (SST). This standard is applicable to the testing and analysis of modified and unmodified asphalt mixtures.
1.2 This standard is applicable to specimens prepared in a laboratory or cored from a pavement for post-construction analysis. It is intended for use with specimens having the following minimum dimensions:Nominal maximum aggregate size is defined in AASHTO R35 as one sieve larger than the first sieve to retain more than 10 % of the total aggregate. Asphalt mixtures with a nominal maximum aggregate size greater than 19 mm can be tested using this procedure, but it is not recommended. The larger aggregate sizes may significantly interfere with the material response, thereby affecting the repeatability of the test.Note 2
The SST shall accommodate test specimens of 150 mm in diameter and 50 mm in height. The specimen height of 50 mm is preferred, but may not be available in roadway cores where layer thickness may be less. If the specimen height is less than 50 mm, use platen to platen fixturing (Linear Variable Differential Transformers (LVDTs) or extensometers). Specimen heights less than 38 mm cannot be tested because of equipment constraints.Note 3
The diameter-to-height ratio for shear test specimens should be 3:1 or greater. This effectively eliminates the use of 100 mm diameter specimens (because of minimum height requirement for testing discussed in NOTE 2).
1.3 The between laboratory reproducibility of this test method has not been determined, therefore this standard should not be used for acceptance or rejection of a material for purchasing purposes.
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.
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Designation:D7312–07
Standard Test Method for
Determining the Permanent Shear Strain and Complex
Shear Modulus of Asphalt Mixtures Using the Superpave
Shear Tester (SST)
This standard is issued under the fixed designation D7312; 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 1.4 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
1.1 This standard provides performance-related test proce-
responsibility of the user of this standard to establish appro-
dures for the determination of stiffness complex shear modulus
priate safety and health practices and determine the applica-
and permanent shear strain of asphalt mixtures using the
bility of regulatory limitations prior to use.
Superpave Shear Tester (SST). This standard is applicable to
the testing and analysis of modified and unmodified asphalt
2. Referenced Documents
mixtures.
2.1 ASTM Standards:
1.2 This standard is applicable to specimens prepared in a
D75 Practice for Sampling Aggregates
laboratory or cored from a pavement for post-construction
D140 Practice for Sampling Bituminous Materials
analysis. It is intended for use with specimens having the
D979 Practice for Sampling Bituminous Paving Mixtures
following minimum dimensions:
D2041 Test Method for Theoretical Maximum Specific
Nominal Maximum Aggregate Specimen Specimen
Gravity and Density of Bituminous Paving Mixtures
Size in Asphalt Mixture Diameter Height
D2726 Test Method for Bulk Specific Gravity and Density
19 mm 150 mm 50 mm
of Non-Absorptive Compacted Bituminous Mixtures
12.5 mm, 9.5 mm, 4.75 mm 150 mm 38 mm
D3203 Test Method for Percent Air Voids in Compacted
NOTE 1—Nominal maximum aggregate size is defined in AASH-
Dense and Open Bituminous Paving Mixtures
TO R35 as one sieve larger than the first sieve to retain more than 10 %
D3549 Test Method for Thickness or Height of Compacted
of the total aggregate. Asphalt mixtures with a nominal maximum
Bituminous Paving Mixture Specimens
aggregate size greater than 19 mm can be tested using this procedure, but
D5361 Practice for Sampling Compacted Bituminous Mix-
it is not recommended. The larger aggregate sizes may significantly
interfere with the material response, thereby affecting the repeatability of tures for Laboratory Testing
the test.
D6752 Test Method for Bulk Specific Gravity and Density
NOTE 2—The SST shall accommodate test specimens of 150 mm in
of Compacted Bituminous Mixtures Using Automatic
diameter and 50 mm in height. The specimen height of 50 mm is
Vacuum Sealing Method
preferred, but may not be available in roadway cores where layer
D6857 Test Method for Maximum Specific Gravity and
thickness may be less. If the specimen height is less than 50 mm, use
Density of Bituminous Paving Mixtures Using Automatic
platen to platen fixturing (Linear Variable Differential Transformers
Vacuum Sealing Method
(LVDTs) or extensometers). Specimen heights less than 38 mm cannot be
tested because of equipment constraints. D6925 Test Method for Preparation and Determination of
NOTE 3—The diameter-to-height ratio for shear test specimens should
the Relative Density of Hot Mix Asphalt (HMA) Speci-
be 3:1 or greater. This effectively eliminates the use of 100 mm diameter
mens by Means of the Superpave Gyratory Compactor
specimens (because of minimum height requirement for testing discussed
E1 Specification for ASTM Liquid-in-Glass Thermometers
in Note 2).
E4 Practices for Force Verification of Testing Machines
1.3 The between laboratory reproducibility of this test
2.2 AASHTO Standards:
methodhasnotbeendetermined,thereforethisstandardshould
AASHTO R35 Superpave Volumetric Design for Hot Mix
not be used for acceptance or rejection of a material for
Asphalt (HMA)
purchasing purposes.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
This test method is under the jurisdiction of ASTM Committee D04 on Road Standards volume information, refer to the standard’s Document Summary page on
and Paving Materials and is the direct responsibility of Subcommittee D04.26 on the ASTM website.
Fundamental/Mechanistic Tests. Available from American Association of State Highway and Transportation
Current edition approved March 1, 2007. Published March 2007. DOI: 10.1520/ Officials (AASHTO), 444 N. Capitol St., NW, Suite 249, Washington, DC 20001,
D7312-07. http://www.transportation.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D7312–07
AASHTO R30 Short and Long Term Aging of Hot Mix The loading device shall be capable of meeting the minimum
Asphalt (HMA) requirements specified in Table A1.1.
6.1.2 Environmental Chamber—The environmental cham-
3. Terminology
ber shall be capable of maintaining the temperature of the test
specimen as specified in Table A1.1 during the testing se-
3.1 Definitions:
quence.
3.1.1 complex shear modulus—a complex number that de-
fines the relationship between shear stress and strain for a 6.1.3 Data Acquisition and Control System—The data ac-
quisition and control system shall automatically control user-
linear viscoelastic material, G*.
3.1.2 permanent shear strain—the non-recoverable shear selected measurement parameters, within the accuracy speci-
strain resulting from a shear load. fiedinTableA1.1,duringthetestingsequence,andshallrecord
load cycles, applied horizontal and vertical loads, specimen
3.1.3 phase angle—a measure of the time lag between the
applied stress and resulting strain, or applied strain and deformation in two directions (vertical and horizontal), envi-
ronmental conditions, and the required frequency of data
resulting stress, in a viscoelastic material.
sampling.Attheconclusionofthetest,thedataacquisitionand
control system shall provide all applicable test data. The load
4. Summary of Test Method
shall be measured by load cells, and the axial and shear
4.1 This test method includes two procedures.
deformations shall be measured by LinearVariable Differential
4.1.1 In the frequency sweep test, the test initiates from a
Transformers (LVDTs) meeting the requirements of Table
zeroshearloadandzeroshearstrain.Repeatedsinusoidalshear
A1.1.
loading oscillates around zero through ten frequencies at a
given temperature while a varying axial load is applied to
NOTE 5—The user can view the wave or pulse parameters on the
prevent dilation of the specimen. The loads and deformations
oscilloscope during the test and/or plot the raw data after the test to
are used to calculate the complex shear modulus and phase confirm that the test met the user-selected load and strain levels.
angle of the specimen at each frequency.
6.2 Conditioning Chamber—The conditioning chamber
4.1.2 In the repeated shear at constant height test, a repeated
shall be capable of maintaining the specimen conditioning
haversine shear stress is applied to the specimen while a
temperatures as specified in Table A1.1.
varying axial load prevents dilation. The accumulated shear
6.3 Platen-Specimen Assembly Device (Optional)—The
deformation at the end of the test is measured to determine the
platen-specimen assembly device is used to facilitate bonding
permanent shear strain.
the specimen to the loading platens with adhesive. The device
shallmaintaintheplatensinaparallelposition(relativetoeach
5. Significance and Use
other) during the gluing operation. The platens must remain
5.1 The test procedures and associated analysis techniques
parallel so that stresses do not develop in the specimen when
described in this method can be used to determine complex
the specimen-platen assembly is clamped in the test system.At
shear modulus and permanent shear strain of asphalt mixtures.
a minimum, the device shall accommodate test specimens 150
The shear frequency sweep test at constant height can be used
mm in diameter with a height of 38 to 50 mm.
to determine the complex shear modulus of a mixture. The
6.4 Aluminum Loading Platens—Topandbottomaluminum
repeated shear test at constant height can be used to determine
loading platens at least 6.35 mm greater in diameter than the
permanent shear strain under repeated loading.
diameter of the specimen to be tested and at least 20 mm thick.
NOTE 4—The complex shear modulus is used to characterize the shear The bearing face of each platen shall be planar to 0.025 mm
behavior of the mixture, and the permanent shear strain relates to
across the entire surface.
pavement rutting.
6.5 Adhesive—Quick-set adhesive with a minimum hard-
ened modulus of 2000 MPa for bonding the platens to the
6. Apparatus
specimen ends.
6.1 Shear Test System—The shear test system shall consist
of a loading device, specimen deformation measurement NOTE 6—Devcon 10240 5-Minute Plastic Steel Epoxy Cement and
Devcon 10110 2-Hour Plastic Steel Epoxy Cement or equivalents have
equipment, an environmental chamber, and a control and data
been used satisfactorily. A ruggedness experiment comparing these two
acquisition system. At a minimum, it shall accommodate test
epoxies showed that glue type was not significant
specimens 150 mm in diameter and 38 to 50 mm in height.
6.1.1 Loading Device—The loading device shall be capable
6.6 Thermometer—A calibrated liquid-in-glass thermom-
of simultaneously applying both vertical and horizontal loads
eter of suitable range with subdivisions readable to 0.1°C
to a specimen. It shall also be capable of applying static,
(0.2°F) or any other thermometric device of equal accuracy,
ramped (increasing or decreasing), and repetitive loads of
precision, and sensitivity shall be used. Thermometers shall
various waveforms.At a minimum, the loading device shall be
conform to the requirements of Specification E1.
capable of applying horizontal shear load pulses in a haversine
waveformwithaloaddurationof0.1swith0.6sbetweenload
pulses. Loading shall be provided by two hydraulic actuators
”Devcon”andallitsrelatedusesandtermsaretrademarkedandcopyrightITW
(one each horizontal and vertical) and shall be controlled by
Devcon, 685 Galt Industrial Blvd. City: St. Louis State: MO ZIP: 63132-1021.
closed-loop feedback using either stress or strain control
Anderson and McGennis, Journal of the Association of Asphalt Paving
throughout the entire range of frequencies and temperatures. Technologists, Vol 72, 2003.
D7312–07
7. Test Specimens 7.2.6 Determine the maximum specific gravity of the mix-
ture in accordance with Test Method D2041 or D6857 and the
7.1 Prepare test specimens according to 7.2, 7.3 or 7.4,as
bulk specific gravity of each test specimen in accordance with
appropriate.Testatleastthreespecimensforeachprocedure(A
TestMethodD2726orD6752.Calculatetheairvoidcontentof
or B).
each specimen in accordance with Test Method D3203.
NOTE 7—Testing additional samples, typically five total, will produce a
7.3 Field-Mixed, Laboratory-Compacted (FMLC)
more accurate test result.
Specimens—Obtain HMAsamples in accordance with Practice
D979. Compact specimens according toTest Method D6925 to
7.2 Laboratory-Mixed, Laboratory-Compacted (LMLC)
the appropriate percentage of air voids (see 7.2.4 and Notes
Specimens—Sample asphalt binder and aggregates in accor-
8-10).
dance with Practices D140 and D75, respectively. Use the
appropriate proportions of asphalt binder and aggregates ac- 7.3.1 Allow the compacted mixture specimens to cool
cording to the final asphalt mix design. completely to room temperature. Cut the specimens to the
7.2.1 Prepare aggregate batches of the appropriate mass to proper test dimensions. Determine and record the height of the
test specimens in accordance with Test Method D3549.To
produce a compacted specimen 150 mm in diameter and
135 6 5 mm in height at the appropriate air void content. Heat verify that the specimen faces are parallel, determine the
minimumandmaximumheightofeachindividualspecimen.If
the aggregate batches to the appropriate mixing temperature.
the difference between the minimum and maximum height is
NOTE 8—Appendix X1 contains information on the calculation of the
more than 2.0 mm, then discard that specimen and prepare
appropriate aggregate batch weight to achieve the correct specimen
another.
dimension at the proper percentage of air voids.
7.3.2 Determine the maximum specific gravity of the mix-
7.2.2 Heat the asphalt binder to the appropriate mixing
ture in accordance with Test Method D2041 or D6857 and the
temperature. Mix the correct proportions of asphalt binder and
bulk specific gravity of each test specimen in accordance with
combined aggregates to match the asphalt mix design.
TestMethodD2726orD6752.Calculatetheairvoidcontentof
7.2.3 Condition the asphalt mixture for 4 h 6 5 min at 135
each specimen in accordance with Test Method D3203.
6 3°C in accordance with AASHTO R30.
7.4 Field-Mixed, Field-Compacted (FMFC or Pavement
7.2.4 Compact the asphalt mixture specimen following Test
Core) Specimens—Obtain asphalt pavement specimens having
Method D6925 to produce test specimens with the required air
a diameter of 150 mm and a minimum thickness of 38 mm in
voids.
accordance with Practice D5361.
Test Air Voids in Test Specimen
7.4.1 Cut the specimens to the proper test dimensions.
Determine the height and diameter of the test specimens in
Shear Frequency Sweep (Procedure A) 7.0 6 0.5 %
Repeated Shear at Constant Height (Procedure B) 3.0 6 0.5 %
accordance with Test Method D3549. To verify that the
specimen faces are parallel, determine the minimum and
NOTE 9—Compaction procedures other than the Superpave gyratory
maximum height of each individual specimen. If the difference
compactor and other target air void percentages may be used. However,
between the minimum and maximum height is more than 2.0
the user should be careful with comparing asphalt mixtures with different
target air voids or compaction. The test procedures and analyses are mm, then discard that specimen and cut another.
sensitive to both the percentage of air voids and the compaction
7.4.2 Determine the maximum specific gravity of the mix-
procedure.
ture in accordance with Test Method D2041 or D6857 and the
NOTE 10—Specimens are often compacted to a target air void percent-
bulk specific gravity of each test specimen in accordance with
agethatishigherthantheanticipatedpercentageofairvoidsinthecuttest
TestMethodD2726orD6752.Calculatetheairvoidcontentof
specimen.This is done because cutting the top and botto
...
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