1、Designation: C 689 09Standard Test Method forModulus of Rupture of Unfired Clays1This standard is issued under the fixed designation C 689; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in pare
2、ntheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method covers the determination of the modu-lus of rupture of ceramic whiteware clays both dry and afterconditioning at 50 or 80 % relativ
3、e humidity, or both.1.2 The values stated in inch-pound units are to be regardedas standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.3 This standard does not purport to address all of thesafety co
4、ncerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C 322 Practice for Sampling Ceramic W
5、hiteware Clays3. Significance and Use3.1 The purpose of this test method is to obtain values ofrupture modulus of clays before firing, under various process-ing conditions (relative humidity).4. Apparatus4.1 Conditioning CabinetAny suitable airtight cabinetwith means for circulating air, or vacuum d
6、esiccator, whereinprescribed specimens can be conditioned as desired beforetesting. Specimens for dry strength shall be stored with silicagel desiccant. Specimens for 50 % relative humidity shall bestored over a saturated solution of sodium dichromate(Na2CR2O72H2O), and specimens for 80 % relative h
7、umidityshall be stored over a saturated solution of ammonium chloride(NH4Cl).4.2 Testing MachineAny suitable testing machine may beused, provided a uniform rate of direct loading can bemaintained at no more than 1 lb/min (4.4 N/min) using theprescribed specimens. For the support of the test specimen
8、, twosteel bars having a diameter of 0.5-in. (12.7-mm) shall beprovided. The load shall be applied by means of a third steelbar having a diameter of 0.5-in. (12.7-mm). All three bars areto be smooth polished steel without surface defects such asscratches or gouges.5. Test Specimen Preparation5.1 Pre
9、paration of Extruded Specimens100 % clay speci-men preparation: The test sample shall be blunged withsufficient distilled water to give complete dispersion andproduce a slip of sufficient viscosity to avoid noticeable settlingof particles (usually in the range of 25 to 50 percent solids).Slip shall
10、be sieved through a No. 120 (125 m) sieve orequivalent. After aging 24 h the slip shall be dewatered to aplastic condition preferably by filter pressing. At this point themoisture content must be adjusted to optimum conditions forforming by some measure of plasticity such as Pfefferkornapparatus, pl
11、umb bob penetration, or other acceptable means.After the water of plasticity has been adjusted (usually willrange from 20 to 50 %), test specimens shall be formed byextrusion. Where hand-operated extruder is used withoutvacuum, the plastic clay shall be thoroughly hand-wedged toeliminate entrapped a
12、ir as a preliminary to forming test pieces.Where a vacuum extruder is used, a vacuum of not less than 25in. (635 mm) Hg shall be maintained during forming operation.5.1.1 Clay-Flint Specimensto be used in the case ofstrong clays that are considered bonding materials. Preparespecimens as in 5.1 using
13、 a mixture of clay and 200 meshpotters flint in a 1/1 ratio blend that has been thoroughly drymixed.5.1.2 Solid Cast Specimens100 % clay and clay-flintspecimens should be prepared by making a high solids slurrydeflocculated to minimum viscosity. Adjust the solids content1This test method is under th
14、e jurisdiction ofASTM Committee C21 on CeramicWhitewares and Related Products and is the direct responsibility of SubcommitteeC21.04 on Raw Materials.Current edition approved Jan. 1, 2009. Published February 2009. Originallyapproved in 1971. Last previous edition approved in 2003 as C 689 03a.2For r
15、eferenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1*A Summary of Changes section appears at the end of this standard.
16、Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.of the slurry to obtain a viscosity between 100-500 cps. Theslurry should be cast in plaster molds until solid, and the barsthen dried in accordance to the procedure outlined in 5.3 and5
17、.4.5.2 DimensionThe test specimens shall be round bars of0.50 (12.8 mm) diameter, and at least 4.5 in. (114 mm) inlength to permit an overhang of at least 0.25 in. at each endwhen mounted on the supports.5.3 Handling and WarpageAll due precaution shall beobserved in the forming and drying to produce
18、 straight testspecimens. No specimen shall be used that shows a warpagegreater than 1 % of its overall length. The bars shall be checkedfrom time to time during drying for straightness, and beforethey stiffen, corrective straightening may be encouraged byrotating the bars so that drying occurs from
19、another surfaceregion. Defective bars due to warpage, flaws, or voids shall berejected.5.4 Drying and StorageThe extruded specimens shall beplaced on a lightly oiled pallet and allowed to dry at roomatmospheric conditions 68 to 104F (20 to 40C) for 24 h. Thenthe specimens shall be dried in a drier a
20、t 140F (60C) and lowrelative humidity for 6 h, or until moisture content is less than0.5 %. The bars shall be loosely stacked in the desiccator topermit rapid cooling. Bars should be cooled to near roomtemperature but not longer than one (1) hour. After the initialdrying period, the specimens for dr
21、y strength shall be furtherdried at 212 to 230F (100 to 110C) for 24 h and then cooledin a desiccator before testing. The bars shall be loosely stackedin the desiccator to permit rapid cooling. Bars should be cooledto near room temperature but not longer than one (1) hour.After the initial drying, t
22、he specimens for testing at 50 or 80 %relative humidity shall be placed into the conditioning cabinetwith circulating air (or in partial vacuum) with a saturatedsolution of sodium dichromate or ammonium chloride, respec-tively, and in each case, stored for 24 h to allow equilibriumconditions to be r
23、eached.6. Procedure6.1 Test at least ten specimens at room temperature for eachcondition, whether dry or conditioned, at 50 or 80 % relativehumidity.6.2 Remove the test specimen from storage, one at a time,and immediately place on the round bar supports of the testingmachine. These supports shall be
24、 spaced 4 in. (102 mm) apart,depending on the type machine and type clay, and testspecimen must overlap each support by at least 0.25 in. (6.4mm). Apply the load at right angles to the specimen andmidway between the supports. Apply the load at a uniform ratenot to exceed 1 lb-f/min (4.4 N/min) until
25、 failure occurs. Theloading rate should be such as to cause failure in approximatelyone minute. Measure the diameter at the break to the nearest0.001 in. (0.03 mm). Use the average of at least three diameterreadings around the bar.7. Calculation7.1 Calculate the modulus of rupture for each specimen
26、asfollows:M 5 8PL/pd3(1)where:M = modulus of rupture, psi (or MPa),P = load at rupture, lbf (or N),L = distance between supports, in. = 2.0 or 4.0 (51 or 102mm), andd = diameter of specimen, in. (or mm).8. Report8.1 Report the following information:8.1.1 Identification of the material tested,8.1.2 D
27、ata and computed modulus of rupture for eachspecimen,8.1.3 Adjusted average of the computed modulus of rupturevalues (discarding those values from the bars which, uponinspection, show obvious defects), or deviate more than 6 10%from the adjusted avaerage. Average again.8.1.4 Drying and storage condi
28、tions; that is, whether the testspecimens were bone dry, or conditioned at 50 or 80 % relativehumidity,8.1.5 Percent moisture of extruded bars,8.1.6 Nominal diameter of bars,8.1.7 Length of span (distance between supports).8.2 The report may also include:8.2.1 Percent moisture of each specimen at te
29、sting,8.2.2 Description of type of fracture and the behavior underload of each specimen,8.2.3 Name and rating of the machine used to make the test,and8.2.4 Curve sheet showing the individual values of modulusof rupture arranged in ascending order.9. Precision and Bias9.1 PrecisionThe precision of th
30、is test method is approxi-mately 610 % of the average modulus of rupture value for thebone dry specimens when the measurements are made by anexperienced operator.9.2 BiasThe bias of this test method cannot be specified.10. Keywords10.1 clay; modulus of ruptureC689092SUMMARY OF CHANGESCommittee C21 h
31、as identified the location of selected changes to this standard since the last issue (C 68903a)that may impact the use of this standard.(1) Added 1.2 concerning use of units, with subsequentrenumbering of the safety caveat in the Scope.(2) Added Section 3 on Significance and Use, with subsequentrenu
32、mbering of all remaining sections.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the risko
33、f infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this
34、standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake yo
35、ur views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).C689093
