ASTM C689-93(1997)e1

Standard Test Method for Modulus of Rupture of Unfired Clays

SCOPE
1.1 This test method covers the determination of the modulus of rupture of ceramic whiteware clays both dry and after conditioning at 50 or 80% relative humidity, or both.  
1.2 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-Dec-1996
• ICS: 91.100.15 - Mineral materials and products
• Technical Committee: C21 - Ceramic Whitewares and Related Products
• Drafting Committee: C21.04 - Raw Materials

Relations

• Replaced By: ASTM C689-03 - Standard Test Method for Modulus of Rupture of Unfired Clays
• Effective Date: 10-Apr-2003

Standards Content (Sample)

NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
e1
Designation: C 689 – 93 (Reapproved 1997)
Standard Test Method for
Modulus of Rupture of Unfired Clays
This standard is issued under the fixed designation C 689; 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.
e NOTE—Section 9 was added editorially in October 1997.
1. Scope produce a slip of sufficient viscosity to avoid noticeable settling
of particles (usually in the range of 25 to 50 percent solids).
1.1 This test method covers the determination of the modu-
Slip shall be sieved through a No. 120 (125 μm) sieve or
lus of rupture of ceramic whiteware clays both dry and after
equivalent. After aging 24 h the slip shall be dewatered to a
conditioning at 50 or 80 % relative humidity, or both.
plastic condition preferably by filter pressing. At this point the
1.2 This standard does not purport to address all of the
moisture content must be adjusted to optimum conditions for
safety concerns, if any, associated with its use. It is the
forming by some measure of plasticity such as Pfefferkorn
responsibility of the user of this standard to establish appro-
apparatus, plumb bob penetration, or other acceptable means.
priate safety and health practices and determine the applica-
After the water of plasticity has been adjusted (usually will
bility of regulatory limitations prior to use.
range from 20 to 50 %), test specimens shall be formed by
2. Referenced Documents extrusion. Where hand-operated extruder is used without
vacuum, the plastic clay shall be thoroughly hand-wedged to
2.1 ASTM Standards:
eliminate entrapped air as a preliminary to forming test pieces.
C 322 Practice for Sampling Ceramic Whiteware Clays
Where a vacuum extruder is used, a vacuum of not less than 25
3. Apparatus
in. (635 mm) Hg shall be maintained during forming operation.
4.1.1 Clay-Flint Specimens—to be used in the case of
3.1 Conditioning Cabinet—Any suitable airtight cabinet
strong clays that are considered bonding materials. Prepare
with means for circulating air, or vacuum desiccator, wherein
specimens as in 4.1 using a mixture of clay and 200 mesh
prescribed specimens can be conditioned as desired before
potters flint in a 1/1 ratio blend that has been thoroughly dry
testing. Specimens for dry strength shall be stored with silica
mixed.
gel desiccant. Specimens for 50 % relative humidity shall be
4.1.2 Solid Cast Specimens—100 % clay and clay-flint
stored with a saturated solution of sodium dichromate
specimens should be prepared by making a high solids slurry
(Na CR O ·2H O), and specimens for 80 % relative humidity
2 2 7 2
deflocculated to minimum viscosity. Adjust the solids content
shall be stored with a saturated solution of ammonium chloride
of the slurry to obtain a viscosity between 100-500 cps. The
(NH Cl).
slurry should be cast in plaster molds until solid, then dried in
3.2 Testing Machine—Any suitable testing machine may be
accordance to the procedure outlined in 4.3 and 4.4.
used, provided a uniform rate of direct loading can be
4.2 Dimension—The test specimens shall be round bars of
maintained at no more than 1 lb/min (4.4 N/min) using the
0.75 (19.2 mm) diameter, 0.50 (12.8 mm) diameter, 0.25-in.
prescribed specimens. For the support of the test specimen, two
(6.4 mm) diameter, and at least 4.5 in. (114 mm) in length to
steel knife-edges rounded to a 0.250-in. (6.35-mm) radius shall
permit an overhang of at least 0.25 in. at each end when
be provided. The load shall be applied by means of a third steel
mounted on the supports.
knife-edge rounded to a radius of 0.250 in.
4.3 Handling and Warpage—All due precaution shall be
4. Test Specimen Preparation
observed in the forming and drying to produce straight test
specimens. No specimen shall be used that shows a warpage
4.1 Preparation of Extruded Specimens—100 % clay speci-
greater than 1 % of its overall length. The bars shall be checked
men preparation: The test sample shall be blunged with
from time to time during drying for straightness, and before
sufficient distilled water to give complete dispersion and
they stiffen, corrective straightening may be encouraged by
rotating the bars so that drying occurs from another surface
This test method is under the jurisdiction of ASTM Committee C-21 on
region. Defective bars due to warpage, flaws, or voids shall be
Ceramic Whitewares and Related Products and is the direct responsibility of
rejected.
Subcommittee C21.04 on Clays.
Current edition approved July 15, 1993. Published September 1993. Originally
published as C 689 – 71 T. Last previous edition C 689 – 80 (1985)e .
Annual Book of ASTM Standards, Vol 15.02.
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