1、Designation: C349 14Standard Test Method forCompressive Strength of Hydraulic-Cement Mortars(Using Portions of Prisms Broken in Flexure)1This standard is issued under the fixed designation C349; the number immediately following the designation indicates the year oforiginal adoption or, in the case o
2、f revision, the year of last revision. A number in parentheses 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 com-pressive strength of hydraulic-cement mo
3、rtars, using for thetest specimens portions of prisms made and broken in flexurein accordance with Test Method C348.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 Values in SI units shall be obtained by measurement inSI
4、 units or by appropriate conversion, using the Rules forConversion and rounding given in Standard IEEE/ASTM SI10, of measurements made in other units.1.4 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
5、standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. (WarningFreshhydraulic cementitious mixtures are caustic and may causechemical burns to skin and tissue upon prolonged exposure.2)2. Referenced Documents2.1 ASTM St
6、andards:3C109/C109M Test Method for Compressive Strength ofHydraulic Cement Mortars (Using 2-in. or 50-mm CubeSpecimens)C348 Test Method for Flexural Strength of Hydraulic-Cement MortarsC670 Practice for Preparing Precision and Bias Statementsfor Test Methods for Construction MaterialsIEEE/ASTM SI 1
7、0 Standard for Use of the InternationalSystem of Units (SI): The Modern Metric System3. Significance and Use3.1 This method provides a means of obtaining compressivestrength values from the same specimens previously used forflexural strength determinations by Test Method C348. Thecompressive strengt
8、h values are for reference purposes, and notas substitutes for values obtained by Test Method C109/C109M for cement acceptance.4. Apparatus4.1 Bearing PlatesThe bearing plates shall be 25 mm inthickness and shall be made of a hard metal. The surfaces of thebearing plates that are placed in contact w
9、ith the specimensshall be 40.0 6 0.1-mm by 50.8-mm rectangles, with the50.8-mm dimension at right angles to the longitudinal axis ofthe prism. The bearing plate surfaces in contact with thespecimen shall have a Rockwell hardness of not less than 60HRC. These surfaces shall not depart from plane surf
10、aces bymore than 0.01 mm when the plates are new and shall bemaintained within a permissible variation of 0.03 mm.4.2 Device for Aligning Bearing PlatesA device for align-ing the bearing plates to ensure the proper location of the upperplate with reference to the lower plate is shown in Fig. 1.Ifthe
11、upper bearing plate does not have free movement within thealigning plates, these shall be separated from the bottom plateby insertion of 0.05-mm shims on each side of the bottombearing plate, and the two 6-mm pins in the upper bearing platefiled down just sufficiently to permit free up and downmovem
12、ent in the slots at the top of the aligning plates.4.3 Testing MachineThe testing machine shall conform tothe requirements prescribed in Test Method C109/C109M,except that the testing machine shall be of the hydraulic type.5. Test Specimens5.1 Both portions from each prism broken in flexure shall be
13、used for compression testing, except that the broken portions ofprisms selected for the compression test shall have a length ofnot less than 65 mm and shall be free of cracks, chippedsurfaces, or other obvious defects.6. Procedure6.1 Determination of Compressive StrengthDuring theinterval between fl
14、exure tests of the prisms and testing the1This test method is under the jurisdiction of ASTM Committee C01 on Cementand is the direct responsibility of Subcommittee C01.27 on Strength.Current edition approved Dec. 1, 2014. Published January 2015. Originallyapproved in 1954. Last previous edition app
15、roved in 2008 as C349 08. DOI:10.1520/C0349-14.2See the section on Safety, Manual of Cement Testing, Annual Book of ASTMStandards, Vol 04.01.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volu
16、me information, refer to the standards Document Summary page onthe ASTM website.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1FIG. 1 Bearing Plates and Bearing Plate A
17、ligning Device for Testing 40 by 40 by 160-mm Mortar Prisms as Modified CubesC349 142broken portions as modified cubes, cover the specimens for the24-h test with waterproof plastic and completely immerse allother specimens in water at a temperature of 23 6 2.0C untilthe time of testing. Wipe the spe
18、cimen to a surface-drycondition, and remove any sand grains or incrustations fromthe faces that will be in contact with the bearing plates of thetesting apparatus. Check these faces by application of astraightedge. If there is appreciable curvature, grind the face orfaces to plane surfaces or discar
19、d the specimen (Note 1).Center the pedestal usually provided for breaking 50 by100-mm cylinders on the base bearing block of the machine,and center the bearing plate assembly on top of this pedestal. Ifthe testing machine has no provisions for automatic accuratecentering of a pedestal exactly below
20、the center of its upperspherical bearing head, a hardened steel cylinder of suitablediameter and height and with parallel plane end faces may beused, provided that the bearing plate assembly is centeredaccurately below the center of the upper bearing head after thespecimen has been placed in proper
21、position in the bearingplate assembly. Apply the specimen aligning guide to theoutside of one of the aligning plates of the bearing plateassembly, with the lugs at each end resting on or slightly abovethe edge of the bearing face of the bottom plate. Turn thespecimen on its side with respect to its
22、position as molded andplace it in the device with the bottom as molded in contact withthe aligning lugs, holding the aligning guide against thealigning plate firmly with one hand. Then remove the aligningguide without disturbing the position of the specimen andapply the load in accordance with the P
23、rocedure section of TestMethod C109/C109M. The testing of the broken portions asmodified cubes shall follow breaking in flexure within 10 minfor 24-h specimens and within 30 min for all other specimens.NOTE 1Modified Cube FacesResults much lower than the truestrength will be obtained by loading face
24、s of the modified cube that are nottruly plane surfaces. It is essential, therefore, that molds be keptscrupulously clean, as otherwise large irregularities in the surfaces willoccur. Instruments for cleaning molds should always be softer than themetal in the molds to prevent wear. In case grinding
25、of modified cubefaces is necessary, it can be accomplished best by rubbing the specimen ona sheet of fine emery paper or cloth glued to a plane surface, using onlymoderate pressure. Since such grinding is tedious for more than a fewthousandths of an inch or hundredth of a millimetre, it is recommend
26、edthat where more than this is found necessary, the specimen be discarded.7. Calculation7.1 Record the total maximum load indicated by the testingmachine and calculate the compressive strength in megapascalsto the nearest 0.1 MPa, as follows:Sc5 0.00062P (1)where:Sc= compressive strength, MPa, andP
27、= total maximum load, N.8. Faulty Specimens and Retests8.1 Specimens that are manifestly faulty or that result instrengths differing by more than 10 % from the average valueof all test specimens made from the same sample and tested atthe same period shall not be considered in determining thecompress
28、ive strength. After discarding strength values, if lessthan two strength values are left for determining the compres-sive strength at any given period a retest shall be made.NOTE 2Reliable strength results depend upon careful observance ofall of the specified requirements and procedures. Erratic res
29、ults at a giventest period indicate that some of the requirements and procedures have notbeen carefully observed; for example, those covering the testing of themodified cubes, as prescribed in Sections 5 and 6. Specimens exhibitingoblique fractures on breaking, due to improper centering in the compr
30、es-sion machine or to lateral movement of one of the testing machine headsduring loading, will often indicate lower strengths than specimensshowing a normal pyramidal fracture.9. Precision and Bias9.1 PrecisionThe following precision statements are ap-plicable when a test result is the average of co
31、mpressivestrength tests of six modified cubes (using portions of prismsbroken in flexure) molded from a single batch of mortar andtested at the same age.NOTE 3The test results used to calculate precision statistics weretaken from tests on Type I, IA, and IS cements tested at 3, 7, and 28 days,and on
32、 a Type III cement tested at 1, 3, and 7 days.9.1.1 Multilaboratory PrecisionThe multilaboratory coef-ficient of variation has been found to be 6.3 %. Therefore,results of properly conducted tests of single batches by twodifferent laboratories should not differ by more than 17.8 % oftheir average (N
33、ote 4).NOTE 4These numbers represent, respectively, the (1s%) and (d2s%)limits as described in Practice C670.9.1.2 Single-Laboratory PrecisionThe single-laboratorycoefficient of variation has been found to be 3.5 %. Therefore,results of two properly conducted tests of single batches ofmortar made wi
34、th the same materials either on the same day orwithin the same week should not differ from each other bymore than 9.9 % of their average (Note 4).9.2 BiasThe procedure in this test method has no biasbecause the value of compressive strength is defined in termsof the test method.10. Keywords10.1 comp
35、ressive strength; hydraulic-cement mortar;hydraulic-cement strength; mortar strength; strengthFor additional useful information on details of cement test methods, reference may be made to the “Manual of CementTesting,” which appears in the Annual Book of ASTM Standards Vol 04.01.C349 143SUMMARY OF C
36、HANGESCommittee C01 has identified the location of selected changes to this standard since the last issue (C349 08)that may impact the use of this standard. (Approved December 1, 2014)(1) Bearing plate dimensions in 4.1 have been revised. (2) Moved non-mandatory information from 9.1 to Note 3.ASTM I
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