ASTM D7361-07
(Test Method)Standard Test Method for Accelerated Compressive Creep of Geosynthetic Materials Based on Time-Temperature Superposition Using the Stepped Isothermal Method
Standard Test Method for Accelerated Compressive Creep of Geosynthetic Materials Based on Time-Temperature Superposition Using the Stepped Isothermal Method
SIGNIFICANCE AND USE
Use of the SIM decreases the time required for creep to occur and the obtaining of the associated data.
The statements set forth in Section 1.5 are very important in the context of significance and use, as well as scope of the standard.
Creep test data are used to calculate the creep modulus of materials as a function of time. These data are then used to predict the long-term creep deformation expected of geosynthetics used in drainage applications.
Note 1—Currently, SIM testing has focused mainly geonets made from high density polyethylene. Additional testing on other materials is ongoing.
R+H testing is done to establish the range of creep strains experienced in the brief period of very rapid response following the peak of the load ramp.
SCOPE
1.1 This test method covers accelerated testing for compressive creep properties using the Stepped Isothermal Method (SIM).
1.2 The test method is focused on geosynthetic drainage materials such as HDPE geonet specimens.
1.3 The SIM tests are laterally unconfined tests based on time-temperature superposition procedures.
1.4 Ramp and Hold (R+H) tests may be completed in conjunction with SIM tests. They are designed to provide additional estimates of the initial rapid compressive creep strain levels appropriate for the SIM results.
1.5 This method can be used to establish the sustained load compressive creep characteristics of a geosynthetic that demonstrates a relationship between time-dependent behavior and temperature. Results of this method are to be used to augment results of compressive creep tests performed at 20 ± 1°C and may not be used as the sole basis for determination of long term compressive creep behavior of geosynthetic material.
1.6 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.7 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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Standards Content (Sample)
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Designation: D7361 − 07
StandardTest Method for
Accelerated Compressive Creep of Geosynthetic Materials
Based on Time-Temperature Superposition Using the
Stepped Isothermal Method
This standard is issued under the fixed designation D7361; 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 D1621Test Method for Compressive Properties of Rigid
Cellular Plastics
1.1 Thistestmethodcoversacceleratedtestingforcompres-
D2990Test Methods forTensile, Compressive, and Flexural
sive creep properties using the Stepped Isothermal Method
Creep and Creep-Rupture of Plastics
(SIM).
D4439Terminology for Geosynthetics
1.2 The test method is focused on geosynthetic drainage
D5262Test Method for Evaluating the Unconfined Tension
materials such as HDPE geonet specimens.
Creep and Creep Rupture Behavior of Geosynthetics
D6364Test Method for Determining Short-Term Compres-
1.3 The SIM tests are laterally unconfined tests based on
time-temperature superposition procedures. sion Behavior of Geosynthetics
1.4 Ramp and Hold (R+H) tests may be completed in
3. Terminology
conjunction with SIM tests. They are designed to provide
additional estimates of the initial rapid compressive creep
3.1 Definitions—For definitions related to geosynthetics see
strain levels appropriate for the SIM results.
Terminology D4439.
1.5 This method can be used to establish the sustained load
3.2 Definitions—For definitions related to creep see Test
compressive creep characteristics of a geosynthetic that dem-
Methods D2990, D5262 and D4439.
onstrates a relationship between time-dependent behavior and
3.3 Definitions of Terms Specific to This Standard:
temperature. Results of this method are to be used to augment
3.3.1 viscoelastic response—refers to polymeric creep,
results of compressive creep tests performed at 20 6 1°C and
strain, stress relaxation or a combination thereof.
may not be used as the sole basis for determination of long
term compressive creep behavior of geosynthetic material.
3.3.2 compressive creep—time-dependent deformation that
occurswhenaspecimenissubjectedtoaconstantcompressive
1.6 The values stated in SI units are to be regarded as the
load.
standard. The values given in parentheses are for information
only.
3.3.3 time-temperature superposition—the practice of shift-
ing viscoelastic response curves obtained at different tempera-
1.7 This standard does not purport to address all of the
tures along a horizontal log time axis so as to achieve a master
safety concerns, if any, associated with its use. It is the
curve covering an extended range of time.
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
3.3.4 shift factor—the displacement along the log time axis
bility of regulatory limitations prior to use.
by which a section of the creep or creep modulus curve is
moved to create the master curve at the reference temperature.
2. Referenced Documents
Shift factors are denoted by the symbol ~ when the displace-
2.1 ASTM Standards:
mentsaregenerallytoshortertimes(attenuation)orthesymbol
a when the displacements are generally to longer times
T
(acceleration).
This test method is under the jurisdiction of ASTM Committee D35 on
Geosynthetics and is the direct responsibility of Subcommittee D35.02 on Endur-
3.3.5 stepped isothermal method (SIM)—a method of expo-
ance Properties.
sure that uses temperature steps and dwell times to accelerate
Current edition approved Dec. 1, 2007. Published March 2008. DOI: 10.1520/
creep response of a material being tested under load.
D7361-07.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
3.3.6 mean test temperature—the arithmetic average of all
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
temperature readings of the atmosphere surrounding the test
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. specimen for a particular temperature step, starting at a time
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7361 − 07
not later than established temperature ramp time, and finishing 6.2.4.1 temperature measurement and control facilities,
at a time just prior to the subsequent temperature reset. 6.2.5 other environmental measurement and control, and
6.2.6 computer data acquisition and control.
3.3.7 offset modulus method or pointing—data analysis
method used to normalize any prestrain in the samples by
7. Sampling
shifting the origin of a stress vs. strain curve to an axis origin
7.1 ThespecimensusedforR+HandSIMtestsshouldallbe
of coordinates, that is, to coordinates (0,0).
taken from the same sample.
3.3.8 ramp and hold (R+H) test—a creep test of very short
7.2 Remove one (1) test specimen from the sample for each
duration, for example, 100–1000 seconds.
SIM test.
3.3.9 dwell time—time during which conditions (particular
7.3 Remove one (1) test specimen from the sample for each
load) are held constant between temperature steps.
R+H test.
3.3.10 compressive creep modulus—in SIM analysis, the
load divided by the percent compressive strain at any given
8. Test Specimens
point in time.
8.1 Specimensshouldbeatleast120mm×120mm(4.7in.
4. Summary of Test Method
× 4.7 in.).
4.1 SIM—Aprocedure whereby specified temperature steps
8.2 Number of tests—
and dwell times are used to accelerate viscoelastic creep
8.2.1 A single specimen is usually sufficient to define a
characteristics during which strain and load are monitored as a
master creep or relaxation curve using the SIM. However, if
function of time.
only a single SIM test is to be performed, the location of the
4.1.1 compressive creep—Constant compressive load in
onset of creep strain or modulus curve should be confirmed
conjunction with specified temperature steps and dwell times
using at least two R+H tests.
are used to accelerate compressive creep strain response.
9. Conditioning
4.2 R+H—Test specimens are ramp loaded at a predeter-
9.1 Compression testing via Test Method D6364 and SIM
mined loading rate to a predetermined load and held under
testing shall be conducted using 20 6 1° C as the reference or
constant load (short term creep test).
temperature standard. If the laboratory is not within this range,
5. Significance and Use
perform tests in a suitable environmental chamber capable of
controlled cooling and heating. The environmental chamber
5.1 Use of the SIM decreases the time required for creep to
should have a programmable- or set-point controller so as to
occur and the obtaining of the associated data.
maintaintemperatureto20 61°C.Whenagreedto,areference
5.2 The statements set forth in Section 1.5 are very impor-
temperatureotherthan20°Ccanbeutilized.Also,whenagreed
tant in the context of significance and use, as well as scope of
to,theresultsoftestingunderthisstandardcanbeshiftedfrom
the standard.
one reference temperature to another.
5.3 Creep test data are used to calculate the creep modulus
9.2 Allow the specimen adequate time to come to tempera-
of materials as a function of time. These data are then used to
ture equilibrium in the laboratory or environmental chamber.
predict the long-term creep deformation expected of geosyn-
Generally, this can be accomplished within a few hours (see
thetics used in drainage applications.
Note 2).
NOTE1—Currently,SIMtestinghasfocusedmainlygeonetsmadefrom
9.3 Record the relative humidity in the laboratory or envi-
high density polyethylene. Additional testing on other materials is
ronmental chamber for all tests.
ongoing.
5.4 R+H testing is done to establish the range of creep
10. Selection of Test Conditions
strains experienced in the brief period of very rapid response
10.1 The standard environment for testing is dry, since the
following the peak of the load ramp.
effect of elevated temperature is to reduce the humidity of
ambient air without special controls.
6. Apparatus
10.2 The standard reference temperature is 20°C unless
6.1 Loading Platens—Loading platens for SIM and R+H
otherwise agreed to. The individual reference temperature for
tests should conform to Test Method D6364, Standard Test
each SIM test is the average achieved temperature of the first
Method for Determining the Short-Term Compression Behav-
dwell time.
ior of Geosynthetics.
10.3 Testing temperatures are to be within 62°C of the
6.2 Testing Machine—A universal testing machine or a
target test temperatures. It is critically important that the test
dead-weightloadingsystemwiththefollowingcapabilitiesand
specimen has equilibrated throughout its thickness so as to
accessories shall be used for testing:
avoid nonisothermal conditions. Initial trials are necessary to
6.2.1 load measurement and control,
establish this minimum equilibrium time.
6.2.2 strain measurement,
6.2.3 time measurement,
NOTE2—Laboratoryexperiencehassuggestedthattheuseofcalibrated
6.2.4 environmental temperature chamber to facilitate co
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