1、Designation: C 349 02Standard Test Method forCompressive Strength of Hydraulic-Cement Mortars(Using Portions of Prisms Broken in Flexure)1This standard is issued under the fixed designation C 349; the number immediately following the designation indicates the year oforiginal adoption or, in the case
2、 of revision, the year of last revision. A number in parentheses 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 com-pressive strength of hydraulic-cement
3、mortars, using for thetest specimens portions of prisms made and broken in flexurein accordance with Test Method C 348.1.2 The values stated in SI units are to be regarded as thestandard. The values in parentheses are for information only.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 s
5、tandard 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 Sta
6、ndards:C 109/C 109M Test Method for Compressive Strength ofHydraulic Cement Mortars (Using 2-in. or 50-mm CubeSpecimens)3C 348 Test Method for Flexural Strength of HydraulicCement Mortars3C 670 Practice for Preparing Precision and Bias Statementsfor Test Methods for Construction Materials4IEEE/ASTM
7、SI 10 Standard for Use of the InternationalSystem of Units (SI): The Modern Metric System53. 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 C 348. Thecompressive s
8、trength values are for reference purposes, and notas substitutes for values (using 50-mm (2-in.) cubes) obtainedby Test Method C 109/C 109M for cement acceptance.34. Apparatus4.1 Bearing PlatesThe bearing plates shall be not lessthan 25 mm in thickness and shall be made of a hard metal. Thesurfaces
9、of the bearing plates that are placed in contact with thespecimens shall be 40.0 6 0.1-mm by 50.8-mm rectangles,with the 50.8-mm dimension at right angles to the longitudinalaxis of the prism. The bearing plate surfaces in contact with thespecimen shall have a Rockwell hardness of not less than 60HR
10、C. These surfaces shall not depart from plane surfaces 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 foraligning the bearing plates to ensure the proper location of theupper plate with refer
11、ence to the lower plate is shown in Fig.1. If the upper bearing plate does not have free movementwithin the aligning plates, these shall be separated from thebottom plate by insertion of 0.05-mm shims on each side of thebottom bearing plate, and the two 6-mm pins in the upperbearing plate filed down
12、 just sufficiently to permit free up anddown movement in the slots at the top of the aligning plates.4.3 Testing MachineThe testing machine shall conform tothe requirements prescribed in Test Method C 109/C 109M,except that the testing machine shall be of the hydraulic type.5. Test Specimens5.1 Both
13、 portions from each prism broken in flexure shall beused 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
14、of Compressive StrengthDuring theinterval between flexure tests of the prisms and testing thebroken 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 (73 61This test method is unde
15、r the jurisdiction of ASTM Committee C01 on Cementand is the direct responsibility of Subcommittee C01.27 on Strength.Current edition approved June 10, 2002. Published August 2002. Originallypublished as C 349 54 T. Last previous edition C 349 97.2See the section on Safety, Manual of Cement Testing,
16、 Annual Book of ASTMStandards, Vol 04.01.3Annual Book of ASTM Standards, Vol 04.01.4Annual Book of ASTM Standards, Vol 04.02.5Annual Book of ASTM Standards, Vol 14.04.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.SI Equivalentsin.1
17、321451638 0.46212916583478 11116 134 22116 212 3mm 0.8 6.4 7.9 9.5 11.7 13 14.3 16 19 22.2 25 27 44.5 51 52.4 64 76FIG. 1 Bearing Plates and Bearing Plate Aligning Device for Testing 40 by 40 by 160-mm Mortar Prisms as Modified CubesC 34923F) until the time of testing. Wipe the specimen to asurface-
18、dry condition, and remove any sand grains or incrus-tations from the faces that will be in contact with the bearingplates of the testing apparatus. Check these faces by applica-tion of a straightedge. If there is appreciable curvature, grindthe face or faces to plane surfaces or discard the specimen
19、(Note 1). Center the pedestal usually provided for breaking 50by 100-mm (2 by 4-in.) cylinders on the base bearing block ofthe machine, and center the bearing plate assembly on top ofthis pedestal. If the testing machine has no provisions forautomatic accurate centering of a pedestal exactly below t
20、hecenter of its upper spherical bearing head, a hardened steelcylinder of suitable diameter and height and with parallel planeend faces may be used, provided that the bearing plateassembly is centered accurately below the center of the upperbearing head after the specimen has been placed in properpo
21、sition in the bearing plate assembly. Apply the specimenaligning guide to the outside of one of the aligning plates of thebearing plate assembly, with the lugs at each end resting on orslightly above the edge of the bearing face of the bottom plate.Turn the specimen on its side with respect to its p
22、osition asmolded and place it in the device with the bottom as molded incontact with the aligning lugs, holding the aligning guideagainst the aligning plate firmly with one hand. Then removethe aligning guide without disturbing the position of thespecimen and apply the load in accordance with the Pr
23、oceduresection of Test Method C 109/C 109M. The testing of thebroken portions as modified cubes shall follow breaking inflexure within 10 min for 24-h specimens and within 30 min forall 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 0.00062 P (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 thecompres
28、sive 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 re
29、sults 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 comp
30、res-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 c
31、ompressivestrength tests of six modified cubes (using portions of prismsbroken in flexure) molded from a single batch of mortar andtested at the same age. They are applicable to mortars madewith Type I, IA, IS, or III cement tested at 3, 7, or 28 days (1,3, or 7 days for Type III cement).9.1.1 Multi
32、laboratory 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 (Note 3).NOTE 3These numbers represent, respectively, the (
33、1s%) and (d2s%)limits as described in Practice C 670.9.1.2 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 with the same materials either on the same day orwithin th
34、e same week should not differ from each other bymore than 9.9 % of their average (Note 3).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 compressive strength; hydraulic-cement mortar;hydraulic-ceme
35、nt strength; mortar strength; strengthC 3493For additional useful information on details of cement test methods, reference may be made to the “Manual of Cement Testing,” whichappears in the Annual Book of ASTM Standards Vol 04.01.ASTM International takes no position respecting the validity of any pa
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38、ments 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 your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyright
39、ed 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 3494
