ASTM C1144-89(1997)
(Test Method)Standard Test Method for Splitting Tensile Strength for Brittle Nuclear Waste Forms
Standard Test Method for Splitting Tensile Strength for Brittle Nuclear Waste Forms
SCOPE
1.1 This test method is used to measure the static splitting tensile strength of cylindrical specimens of brittle nuclear waste forms. It provides splitting tensile-strength data that can be used to compare the strength of waste forms when tests are done on one size of specimen.
1.2 The test method is applicable to glass, ceramic, and concrete waste forms that are sufficiently homogeneous (Note 1) but not to coated-particle, metal-matrix, bituminous, or plastic waste forms, or concretes with large-scale heterogeneities. Cementitious waste forms with heterogeneities >1 to 2 mm and C496 and Practice C192. Note 1-Generally, the specimen structural or microstructural heterogeneities must be less than about one-tenth the diameter of the specimen.
1.3 This test method can be used as a quality control check on brittle waste forms and may be useful for optimizing waste form processing. Meaningful comparison of waste forms, however, requires data obtained on specimens of one size.
1.4 The values stated in SI units are to be regarded as the standard.
1.5 This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety problems 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. For specific hazard statements, see Section 7.
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Designation: C 1144 – 89 (Reapproved 1997)
Standard Test Method for
Splitting Tensile Strength for Brittle Nuclear Waste Forms
This standard is issued under the fixed designation C 1144; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope C 496 Test Method for Splitting Tensile Strength of Cylin-
drical Concrete Specimens
1.1 This test method is used to measure the static splitting
C 773 Test Method for Compressive (Crushing) Strength of
tensile strength of cylindrical specimens of brittle nuclear
Fired Whiteware Materials
waste forms. It provides splitting tensile-strength data that can
D 2938 Test Method for Unconfined Compressive Strength
be used to compare the strength of waste forms when tests are
of Intact Rock Core Specimens
done on one size of specimen.
E 4 Practices for Force Verification of Testing Machines
1.2 The test method is applicable to glass, ceramic, and
2.2 Society of Manufacturing Engineers:
concrete waste forms that are sufficiently homogeneous (Note
Geometrical Tolerance Interpretations, SME Tool and Manu-
1) but not to coated-particle, metal-matrix, bituminous, or
facturing Engineers Handbook
plastic waste forms, or concretes with large-scale heterogene-
ities. Cementitious waste forms with heterogeneities >1 to 2
3. Summary of Test Method
mm and <5 mm can be tested using this procedure provided the
3.1 A right-circular cylinder of the waste solid is loaded
specimen size is increased from the reference size of 12.7 mm
diametrally between two hardened, parallel bearing blocks
diameter by 6 mm length, to 51 mm diameter by 100 mm
positioned between the specimen and the two test machine
length, as recommended in Test Method C 496 and Practice
platens, one of which is moving at a constant speed relative to
C 192.
the other (Fig. 1).
NOTE 1—Generally, the specimen structural or microstructural hetero-
3.2 As the load increases, the resultant stress eventually
geneities must be less than about one-tenth the diameter of the specimen.
reaches the fracture strength of the material, and the specimen
1.3 This test method can be used as a quality control check
splits along the vertical diameter, usually with some subsidiary
on brittle waste forms and may be useful for optimizing waste
fracture at other locations. The splitting tensile strength, T
form processing. Meaningful comparison of waste forms,
(MPa), is calculated from the measured fracture load as
however, requires data obtained on specimens of one size.
follows:
1.4 The values stated in SI units are to be regarded as the
T 5 2P/pLD (1)
standard.
1.5 This standard may involve hazardous materials, opera- where:
P 5 applied force, or fracture load, at initiation of fracture,
tions, and equipment. This standard does not purport to
address all of the safety concerns, if any, associated with its N,
L 5 specimen length, mm, and
use. It is the responsibility of the user of this standard to
D 5 specimen diameter, mm.
establish appropriate safety and health practices and deter-
3.3 The splitting tensile-strength test uses a compressive
mine the applicability of regulatory limitations prior to use.
loading to effect a tensile stress. The stress state in the
For specific hazard statements, see Section 7.
specimen during the test is well documented by both theoreti-
2. Referenced Documents
cal and experimental stress analysis. The stress state is intended
to be biaxial with a uniform tensile stress normal to the loading
2.1 ASTM Standards:
axis across the anticipated fracture plane (the vertical diameter
C 39 Test Method for Compressive Strength of Cylindrical
between loading points). The loading pads tend to prevent
Concrete Specimens
compressive-stress failure near the loading points. In a valid
C 192 Practice for Making and Curing Concrete Test Speci-
test, failure is initiated near the axis of the cylinder and
mens in the Laboratory
1 3
This test method is under the jurisdiction of ASTM Committee C-26 on Nuclear Annual Book of ASTM Standards, Vol 15.02.
Fuel Cycle and is the direct responsibility of Subcommittee C26.07 on Waste Annual Book of ASTM Standards, Vol 04.08.
Materials. Annual Book of ASTM Standards, Vol 03.01.
Current edition approved Nov. 24, 1989. Published January 1990. Available from Society of Manufacturing Engineers, P.O. Box 930, One SME
Annual Book of ASTM Standards, Vol 04.02. Dr., Dearborn, MI 48121.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
C 1144
4. Significance and Use
4.1 The splitting tensile-strength test can be used only on
brittle waste materials such as ceramics, glass, concrete, or
other materials that also have tensile fracture strengths that are
less than one third of the compression strengths.
4.2 The test cannot be used for metal-matrix, bituminous,
plastic, or coated-particle waste forms.
4.3 The strength values derived from this test cannot be
applied to compressive-stress impact failure. The results apply
only to tensile-stress failure. A separate compression-strength
test, in which a cylindrical specimen is loaded on the flat
surfaces, is required to determine compression strength along
the lines of Test Methods C 39, D 2938, and C 773. Failures
caused by impact must be determined in a separate test.
4.4 This test method is applicable only to brittle solids
because these are the only materials that fail under a definable
stress state for the test specimen geometry and loading. For
FIG. 1 Diametral Test Specimen and Apparatus
instance, extensive local shearing at or near the loading points
that will also occur for plastically deformable solids, such as
propagates on the plane defined by the lines of contact of the
ductile metals or viscous polymers, will change the stress
bearing blocks with the specimen (see Fig. 2(a) and Section 5).
distribution sufficiently to invalidate the elastic-stress calcula-
tion used to obtain the tensile stress across the vertical fracture
plane. Ductile materials will not, in many cases, fracture in the
test.
4.5 The effect of specimen size on the measured strength of
brittle materials is not determined by this test method. In some
materials, such as concretes, heterogeneities may be so large
that tests on larger specimens are more representative. Testing
along the lines of Test Method C 496 may then be appropriate
to measure splitting tensile strength.
4.6 This test method does not determine the effects of time
and environment on strength, nor does it address failure under
long-duration static loading.
4.7 This test method can be used as a quality-control check
and for optimizing waste form processing.
5. Interferences
5.1 Visually inspect the specimen after fracture. Disqualifi-
cation is based on the occurrence of compression and shear
failure or failure at an observable surface flaw. See 5.3, 5.4, and
5.5 for guidance in identification of the failure mode. Report
identification of the failure mode in terms relatable to these
sections.
5.2 There are two fracture modes that indicate a valid test,
normal tensile failure and triple-cleft failure, both of which can
be followed by additional severe fragmentation of the center
vertical region of the specimen. A third type of failure, or
fracture, called compression and shear failure, invalidates the
test results. Because of the possible varied fractures and
because there is no satisfactory way to predict which will
occur, the specimen must be examined after the test to qualify
the results.
5.3 Normal Tensile Failure—In normal tensile failure, the
(a) Normal Tensile Failure (Valid Test)
specimen splits along the loaded diameter (see Fig. 2(a)). This
(b) Triple-Cleft Failure (Valid Test)
is the ideal failure and can be used to compute splitting tensile
(c) Compression and Shear Failures (Invalid Test)
FIG. 2 Failure Modes strength. The fracture may not completely extend from one
C 1144
bearing block to the other initially. The load to initiate the 3). Fully annealed OFHC copper foil 0.13 by 0.01-mm thick
fracture is used to calculate strength. (Note 3) is suitable for higher strength waste forms.
5.4 Triple-Cleft Failure—Triple-cleft failure is a variation
NOTE 3—Deviations in pad material sizes of this magnitude will not
on the normal tensile failure, and the specimen splits into four
affect test results.
approximately equal-sized pieces, two on each side of the
6.5 Load-Measurement System—Use a strip-chart or x-y
loaded diameter (see Fig. 2(b)). Tests exhibiting this failure
recorder to obtain a record of the loading force versus time.
also yield valid values of splitting tensile strength. Additional
The recorder must be capable of responding to sudden changes
fragmentation can occur when the fracture is initiated on the
in load (response time <1 s full scale). Use the strip-chart or
diametral plane, as in glasses where the stresses on the central
x-y recorder to record the calibration loads during a check of
unsupported vertical region (after initial splitting) cause frag-
the load-measurement system with dead weights or an electri-
mentation of that region.
cal method prior to testing. Use a load cell that has been
5.5 Compression and Shear Failure— In compression and
verified according to Practice E 4. The chart speed shall be
shear failures, the specimen is crushed near the bearing blocks
appropriate for displaying the elastic or straight-line portion of
without fracturing through the diameter, or the specimen may
the loading at an angle no greater than 80° to the time axis. It
fail near the loading pads due to a local crushing or by
is imperative to have a continuous recording of load to ensure
fracturing at any angle away from the loaded diameter (see Fig.
that the fracture is not missed.
2(c)). In some cases, the specimen may change shape before
fracture or may not fracture at all. Tests with these types of 6.6 Number of Tests—Initially, five valid test results should
failure or deformation cannot be used to compute splitting be obtained. Calculate the percent relative standard deviation
tensile strengths, and stresses calculated from such tests are not of the five measured tensile strengths as follows:
reportable as tensile strengths. Choice of loading pad may
s
RSD ~%!5 · 100 (2)
avoid these types of failure in some cases.
¯
T
6. Apparatus where:
T 5 tensile strength for the ith test, and
i
6.1 Test Temperature—Conduct the test at room tempera-
T 5 the sample mean tensile strength 5 ⁄5 ( T , and
i 5 1 i
ture and report the test temperature.
5 2
¯
s 5 the sample standard deviation 5 ⁄5 ( ( T −T)
i 5 1 i
6.2 Testing Machine—Use a constant crosshead-speed ma-
1/2
.
−4
chine at a speed of 8 3 10 mm/s6 50 % (Note 2). A fixed
6.6.1 If the percent relative standard deviation is less than
loading rate machine is not acceptable. The machine can be
20.1 %, no additional tests are required. If the RSD (%)
either screw driven or otherwise controlled to give a fixed
exceeds 20.1 %, use Table 1 to determine the number of
speed. The stiffness of the various members of the loading
additional tests required. If the RSD (%) is greater than 27.1 %,
system shall be sufficiently high, such that the total deflection
−8
the material has variations in strength that are unusually large.
per unit force is less than 10 m/N, not including the
Report the results of the ten tests in this case.
specimen.
6.6.2 The criterion for the sample sizes given in Table 1 is
NOTE 2—Deviations in crosshead speeds of this magnitude will not
based on the desire that the half-width of the 95 % confidence
affect test results.
interval for the average tensile strength be no greater than 25 %
6.3 Bearing Blocks—Bearing blocks with Rockwell hard-
of that value. If the tensile strength measurements come from
ness >60 HRC are required. Any permanent indentation of the
a normal distribution, this should be approximately true.
bearing block invalidates the test. Suitable materials are tool
Naturally, the actual confidence-interval statements made will
steels hardened from 60 to 65 HRC by conventional heat
be based on the observed sample values, not the desired result.
treatments and ground to obtain a smooth loading surface. The
surfaces of the bearing blocks in contact with the pads shall be
7. Hazards
flat to within 60.03 mm, parallel within 60.03 mm/mm (1.7°)
7.1 Specimens of brittle materials under stress can fracture
measured on each of two perpendicular directions, and perpen-
and produce flying fragments. In addition to other precautions,
dicular to the loading axis within 60.03 mm/mm (1.7°).
take precautions against injury by placing a shield around the
6.4 Pad Materials—The choice of pad material depends on
specimen to stop such fragments.
the strength and elastic modulus of the material tested. A
suitable pad material is one that prevents contact between the
test specimen and the bearing blocks but is soft enough to
TABLE 1 Minimum Number of Required Tests (Based on the
distribute the load over a small area. If the specimen and
Sample % Relative Standard Deviation from Five Tests)
bearing block contact during the test (determined by visual
Sample Relative Standard Number of tests Number of
inspection of the pad after testing), the test result is invalid. In
Deviation, RSD (%) required, (n) additional tests
general, balsa wood is a suitable pad material for testing glass
#20.1 5 0
and other materials with splitting tensile strengths less than
20.2 to 22.1 6 1
approximately 100 MPa. The grain of the wood shall be 22.2 to 23.9 7 2
24.0 to 25.5 8 3
aligned perpendicular to the line of contact between specimen
25.6 to 27.0 9 4
and bearing block with the grain parallel to the bearing block.
$27.1 10 5
The thickness of the balsa wood shall be 1.6 6 0.2 mm (Note
C 1144
TABLE 2 Required Calibration
8. Test Specimens
Instrument and
8.1 Use a specimen that is 12.7 6 0.3 mm in diameter and
Measurement Calibration Reference
Sensitivity
6.4 6 0.15 mm in length, round within a tolerance of 0.025
Specimen caliper micrometer, NIST traceable gage
mm, straight within a tolerance of 0.050 mm, and with the ends
dimensions 0.01 mm or better blocks—every six months
square to the cylinder axis within a tolerance of 0.075 mm; the Specimen caliper micrometer, NIST traceable gage blocks
straightness, 0.01 mm or better and surface plate6 0.001
ends of the specimen are to be parallel within 0.150 mm (Note
roundness, and LVDT g
...
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