ASTM C451-2008 Standard Test Method for Early Stiffening of Hydraulic Cement (Paste Method)《水硬水泥的早硬化的标准试验方法(水泥浆法)》.pdf

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1、Designation: C 451 08Standard Test Method forEarly Stiffening of Hydraulic Cement (Paste Method)1This standard is issued under the fixed designation C 451; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision.

2、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 earlystiffening in hydraulic-cement paste.1.2 The values stated in SI units are to be r

3、egarded asstandard. No other units of measurement are included in thisstandard.1.3 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 dete

4、rmine the applica-bility of regulatory limitations prior to use.WarningFresh hydraulic-cementitious mixtures are caus-tic and may cause chemical burns to skin and tissue uponprolonged exposure. The use of gloves, protective clothing,and eye protection is recommended. Wash contact area withcopious am

5、ounts of water after contact. Wash eyes for aminimum of 15 min. Avoid exposure of the body to clothingsaturated with the liquid phase of the unhardened material.Remove contaminated clothing immediately after exposure.1.4 The text of this standard references notes and footnoteswhich provide explanato

6、ry material. These notes and footnotes(excluding those in tables and figures) shall not be consideredas requirements of the standard.2. Referenced Documents2.1 ASTM Standards:2C 150 Specification for Portland CementC 183 Practice for Sampling and the Amount of Testing ofHydraulic CementC 187 Test Me

7、thod for Normal Consistency of HydraulicCementC 219 Terminology Relating to Hydraulic CementC 305 Practice for Mechanical Mixing of Hydraulic CementPastes and Mortars of Plastic ConsistencyC 670 Practice for Preparing Precision and Bias Statementsfor Test Methods for Construction MaterialsC 1005 Spe

8、cification for Reference Masses and Devices forDetermining Mass and Volume for Use in the PhysicalTesting of Hydraulic CementsD 1193 Specification for Reagent Water3. Terminology3.1 Definitions:3.1.1 early stiffening, nthe early development of stiffnessin the working characteristics of a hydraulic-c

9、ement paste,mortar, or concrete; varieties include false set and flash set.3.1.2 false set, nthe early development of stiffness in theworking characteristics of a hydraulic-cement paste, mortar, orconcrete without the evolution of much heat, which stiffnesscan be dispelled and plasticity regained by

10、 further mixingwithout addition of water; also known as “grab set,” “prema-ture stiffening,” “ hesitation set,” and “rubber set.”3.1.3 flash set, nthe early development of stiffness in theworking characteristics of a hydraulic-cement paste, mortar, orconcrete, usually with the evolution of considera

11、ble heat,which stiffness cannot be dispelled nor can the plasticity beregained by further mixing without addition of water; alsoknown as “quick set.”3.1.4 Refer to Terminology C 219 for definitions of otherterms.4. Summary of Test Method4.1 A paste is prepared with the cement to be tested, usingsuff

12、icient water to give a required initial penetration as mea-sured by the Vicat apparatus at a stipulated time after comple-tion of mixing. A second penetration, termed the final penetra-tion, is measured at a later stipulated time. The ratio of finalpenetration to initial penetration is calculated as

13、 a percentage.5. Significance and Use5.1 The purpose of this test method is to determine thedegree to which a cement paste develops early stiffening or toestablish whether or not a cement complies with a specificationlimit on early stiffening.5.2 When used for establishing compliance with a specifi-

14、cation limit, the specification requirement is customarily statedin terms of the minimum allowable final penetration, in1This test method is under the jurisdiction of ASTM Committee C01 on Cementand is the direct responsibility of Subcommittee C01.30 on Time of Set.Current edition approved June 1, 2

15、008. Published June 2008. Originallyapproved in 1960. Last previous edition approved in 2007 as C 451 07.2For 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 standar

16、ds Document Summary page onthe ASTM website.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.percent, calculated in accordance with the Calculation Section.When used fo

17、r estimating the relative tendency of a cement tomanifest early stiffening, additional information of value maybe obtained if the remix procedure described in the ProcedureSection is employed. Under some conditions, a judgment maybe made by comparing the behavior in the initial test and in theremix

18、procedure to differentiate a relatively less serious andless persistent tendency to early stiffening (false set) from onethat is more persistent and, consequently, more serious (flashset).5.3 Severe false setting in a cement may cause difficultyfrom a placing and handling standpoint, but it is not l

19、ikely tocause difficulties where concrete is mixed for a longer timethan usual, as usually occurs in transit mixing, or where it isremixed prior to placing or transporting, as occurs in concretepumping operations. It is most likely to be noticeable whereconcrete is mixed for a short period of time i

20、n stationary mixersand transported to the forms in non-agitating equipment, suchas on some paving jobs, and when concrete is made in anon-site batch plant.5.4 Cements with severe false setting usually requireslightly more water to produce the same consistency, whichmay be expected to result in sligh

21、tly lower strengths andincreased drying shrinkage.5.5 Early stiffening resulting from false set is not likely tocause a cement to fail the applicable time of setting require-ment.5.6 Early stiffening resulting from flash set, depending onseverity, can cause a cement to fail the applicable time ofset

22、ting requirement.6. Apparatus6.1 Vicat Apparatus, conforming to the requirements of TestMethod C 187.6.2 Flat Trowel, having a sharpened straight-edged steelblade 100 to 150 mm in length. The edges when placed on aplane surface shall not depart from straightness by more than 1mm.6.3 Mixer, Bowl, Pad

23、dle, and Scraper, conforming to therequirements of Practice C 305.6.4 Glass Graduates, 200 or 250 ml capacity, conforming tothe requirements of Specification C 1005.6.5 Masses and Mass Determining Devices, conforming tothe requirements of Specification C 1005. The devices fordetermining mass shall b

24、e evaluated for precision and accuracyat a total load of 1000 g.6.6 Conical Ring, made of a rigid, non-corroding, non-absorbernt material, having a height of 40 6 1 mm, an insidediameter at the bottom of 70 6 3 mm, and an inside diameterat the top of 60 6 3 mm (see Test Method C 187, Fig. 1 itemG).6

25、.7 Plane Non-Absorptive Plate, 100 6 5 mm square, ofsimilar planeness, corrosivity, and absorptivity to that of glass(see Test Method C 187, Fig. 1 item H).6.8 Inspect and document Section 6 apparatus conformanceto the requirements of this test method at least every 212years.7. Reagent7.1 Mixing Wat

26、erPotable water is satisfactory for routinetests. For all referee and cooperative tests, use reagent waterconforming to the requirements of Specification D 1193 forType III or Type IV grades of reagent water.8. Sampling8.1 When the test is part of acceptance testing, sample thecement in accordance w

27、ith Practice C 183.9. Conditioning9.1 Maintain the temperature of the room, dry materials,paddle, bowl, conical ring, and base plate at 23.0 6 3.0 C.Maintain the temperature of the mixing water at 23.0 6 2.0 C.9.2 Maintain the relative humidity of the mixing room at notless than 50 %.10. Procedure10

28、.1 Preparation of Cement PasteMix 500 g of cementwith sufficient water to produce a paste with an initial penetra-tion of 32 6 4 mm using the following procedure.10.1.1 Place the dry paddle and the dry bowl in the mixingposition in the mixer.10.1.2 Introduce the materials for a batch into the bowl a

29、ndmix in the following manner:10.1.2.1 Place all the mixing water in the bowl.10.1.2.2 Add the cement to the water and allow 30 s for thewater to absorb.10.1.2.3 Start the mixer and mix at a slow speed (1406 5r/min) for 30 s.10.1.2.4 Stop the mixer for 15 s, and during this time scrapedown into the

30、batch any paste that may have collected on thesides of the bowl.10.1.2.5 Start the mixer at a medium speed (285 610 r/min)and mix for 212 min.10.2 Molding Test SpecimensQuickly form the cementpaste into a ball with gloved hands. Press the ball, resting in thepalm of one hand, into the larger end of

31、the conical ring heldin the other hand, completely filling the ring with paste.Remove the excess at the larger end by a single movement ofthe palm of the hand. Place the ring on its larger end on thenon-absorptive plate and slice off the excess paste at thesmaller end at the top of the ring by a sin

32、gle oblique stroke ofa sharp-edged trowel held at a slight angle with the top of thering. Smooth the top of the specimen, if necessary, with one ortwo light touches of the pointed end of the trowel. During theoperation of cutting and smoothing, take care not to compressthe paste.10.3 Determination o

33、f Initial PenetrationSet the pasteconfined in the ring resting on the plate, H, under the rod, B,Fig. 1 of Test Method C 187, about one third of the diameterfrom the edge, and bring the plunger end, C, in contact with thesurface of the paste and the tightened setscrew, E. Then set themovable indicat

34、or, F, to the upper zero mark of the scale, andrelease the rod exactly 20 s after completion of the mixing.Keep the apparatus free of all vibrations during the penetrationtest. Consider the paste to have proper consistency when therod settles to a point 32 6 4 mm below the original surface inC451082

35、30 s after being released. Make trial pastes with varyingpercentages of water until this consistency is obtained. Thisconsistency is the initial penetration. During the 30-s intervalfor the initial penetration, return the excess paste to the bowland cover the bowl and mixing paddle with a lid.10.4 D

36、etermination of Final PenetrationAfter completionof the initial reading, remove the plunger from the paste, cleanit, and reset the ring and plate in a new position. Perform thisoperation with as little disturbance as possible to the pasteconfined in the Vicat ring. Then bring the plunger again incon

37、tact with the surface of the paste, tighten the setscrew, andset the movable indicator to the upper zero mark of the scale.Release the plunger a second time 5 min 6 10 s aftercompletion of the mixing period, and determine the finalpenetration 30 s after the plunger is released.10.5 Determination of

38、Remix PenetrationIf the penetra-tions determined by the foregoing procedure show the cementto be stiffening rapidly, at the option of the tester, obtaininformation as to the nature of the stiffening by testing asfollows:10.5.1 After completing the measurement of the 5-minpenetration, immediately ret

39、urn the paste in the ring to thebowl.10.5.2 Start the mixer, raise the bowl into mixing position,and remix the contents of the bowl at a medium speed (285610 r/min) for 1 min.10.5.3 Fill the ring and determine the penetration followingthe procedures specified in 10.2 and 10.3.11. Calculation11.1 Cal

40、culate the percent final penetration, based on theratio of final penetration to initial penetration, as follows:P,%5BA3 100 (1)where:P = percent final penetration,A = initial penetration, mm, andB = final penetration, mm.12. Report12.1 Report the results of the test as follows:Initial penetration _

41、mmFinal penetration _ mmPercent final penetration _ %Remix penetration _ mm13. Precision and Bias13.1 Precision13.1.1 On samples testing between 8 % and 89 % PasteFalse Set, the single-operator (within laboratory) standarddeviation has been found to be 10 % (1s), therefore, results oftwo properly co

42、nducted tests by the same operator on samplesof the same cement should not differ from each other by morethan 28 % (1s and d2s are defined in Practice C 670).13.1.2 On samples testing between 8 % and 89 % PasteFalse Set, the multi-laboratory standard deviation has beenfound to be 12 % (1s), therefor

43、e, results of two properlyconducted tests from two different laboratories on samples ofthe same cement should not differ by more than 34 % (1s andd2s are defined in Practice C 670). (See Note 1.)13.2 Bias13.2.1 Since an acceptable reference material suitable fordetermining any bias of this method do

44、es not exist, nostatement on bias is being made.NOTE 1This data is based upon CCRL Portland Cement round robintest samples 47 to 138. The data indicates that precision decreases as thefalse set values fall below approximately 60 %. These decreases are notclearly statistically significant, however th

45、ey do indicate the duplicationdifficulties on cements which exhibit false set tendencies severe enough tofail or possibly fail Specification C 150 optional limits.14. Keywords14.1 early stiffening; false set; flash set; hydraulic-cementpaste; Vicat.SUMMARY OF CHANGESCommittee C01 has identified the

46、location of selected changes to this test method since the last issue,C 451 07, that may impact the use of this test method. (Approved June 1, 2008)(1) Revised 6.2, 6.5, and 9.2.Committee C01 has identified the location of selected changes to this test method since the last issue,C 451 05, that may

47、impact the use of this test method. (Approved July 15, 2007)(1) Added new 6.8.C451083ASTM 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 th

48、e 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 or withdrawn. You

49、r 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 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 copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United State