1、Designation: C 689 03aStandard 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 par
2、entheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of the modu-lus of rupture of ceramic whiteware clays both dry and afterconditioning at 50 or 80 % relati
3、ve humidity, or both.1.2 This standard does not purport to address all of thesafety concerns, 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 t
4、o use.2. Referenced Documents2.1 ASTM Standards:2C 322 Test Method for Sampling Ceramic Whiteware Clays3. Apparatus3.1 Conditioning CabinetAny suitable airtight cabinetwith means for circulating air, or vacuum desiccator, whereinprescribed specimens can be conditioned as desired beforetesting. Speci
5、mens 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 humidityshall be stored over a saturated solution of ammonium chloride(NH4Cl).3.2 Testing
6、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, twosteel bars having a diameter of 0.5-in. (12.7-mm) shall beprovided. The load shall b
7、e 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.4. Test Specimen Preparation4.1 Preparation of Extruded Specimens100 % clay speci-men preparation: The test sample shall be
8、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 be sieved through a No. 120 (125 m) sieve orequivalent. After aging 24 h the slip shall b
9、e 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, plumb bob penetration, or other acceptable means.After the water of plasticity has been adj
10、usted (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 air as a preliminary to forming test pieces.Where a vacuum extruder is used, a vacuum of n
11、ot less than 25in. (635 mm) Hg shall be maintained during forming operation.4.1.1 Clay-Flint Specimensto be used in the case ofstrong clays that are considered bonding materials. Preparespecimens as in 4.1 using a mixture of clay and 200 meshpotters flint in a 1/1 ratio blend that has been thoroughl
12、y drymixed.4.1.2 Solid Cast Specimens100 % clay and clay-flintspecimens should be prepared by making a high solids slurrydeflocculated to minimum viscosity. Adjust the solids contentof the slurry to obtain a viscosity between 100-500 cps. Theslurry should be cast in plaster molds until solid, and th
13、e barsthen dried in accordance to the procedure outlined in 4.3 and4.4.4.2 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.4.3 Handling and WarpageAll
14、due precaution shall beobserved in the forming and drying to produce 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 straighteni
15、ng may be encouraged by1This test method is under the jurisdiction of ASTM Committee C21 on CeramicWhitewares and Related Products and is the direct responsibility of SubcommitteeC21.04 on Raw Materials.Current edition approved Oct. 1, 2003. Published October 2003. Originallyapproved in 1971. Last p
16、revious edition approved in 2003 as C 689 03.2For referenced 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.1Copyright ASTM
17、International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.rotating the bars so that drying occurs from another surfaceregion. Defective bars due to warpage, flaws, or voids shall berejected.4.4 Drying and StorageThe extruded specimens shall beplaced on a ligh
18、tly 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 at 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 rap
19、id cooling. Bars should be cooled to near roomtemperature but not longer than one (1) hour. After the initialdrying period, the specimens for dry 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 th
20、e desiccator to permit rapid cooling. Bars should be cooledto near room temperature but not longer than one (1) hour.After the initial drying, the specimens for testing at 50 or 80 %relative humidity shall be placed into the conditioning cabinetwith circulating air (or in partial vacuum) with a satu
21、ratedsolution of sodium dichromate or ammonium chloride, respec-tively, and in each case, stored for 24 h to allow equilibriumconditions to be reached.5. Procedure5.1 Test at least ten specimens at room temperature for eachcondition, whether dry or conditioned, at 50 or 80 % relativehumidity.5.2 Rem
22、ove the test specimen from storage, one at a time,and immediately place on the round bar supports of the testingmachine. These supports shall be 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
23、 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 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
24、.03 mm). Use the average of at least three diameterreadings around the bar.6. Calculation6.1 Calculate the modulus of rupture for each specimen 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 10
25、2mm), andd = diameter of specimen, in. (or mm).7. Report7.1 Report the following information:7.1.1 Identification of the material tested,7.1.2 Data and computed modulus of rupture for eachspecimen,7.1.3 Adjusted average of the computed modulus of rupturevalues (discarding those values from the bars
26、which, uponinspection, show obvious defects), or deviate more than 6 10%from the adjusted avaerage. Average again.7.1.4 Drying and storage conditions; that is, whether the testspecimens were bone dry, or conditioned at 50 or 80 % relativehumidity,7.1.5 Percent moisture of extruded bars,7.1.6 Nominal
27、 diameter of bars,7.1.7 Length of span (distance between supports).7.2 The report may also include:7.2.1 Percent moisture of each specimen at testing,7.2.2 Description of type of fracture and the behavior underload of each specimen,7.2.3 Name and rating of the machine used to make the test,and7.2.4
28、Curve sheet showing the individual values of modulusof rupture arranged in ascending order.8. Precision and Bias8.1 PrecisionThe precision of this test method is approxi-mately 610 % of the average modulus of rupture value for thebone dry specimens when the measurements are made by anexperienced ope
29、rator.8.2 BiasThe bias of this test method cannot be specified.9. Keywords9.1 clay; modulus of ruptureASTM 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 de
30、termination of the validity of any such patent rights, and the riskof 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
31、or withdrawn. Your comments are invited either for revision of this 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 t
32、hat your comments have not received a fair hearing you shouldmake your 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).C 689 03a2
