1、Designation: C451 08C451 13Standard Test Method forEarly Stiffening of Hydraulic Cement (Paste Method)1This standard is issued under the fixed designation C451; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revis
2、ion. 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 early stiffening in hydraulic-cement paste.1.2 The values stated in SI units are t
3、o be regarded as standard. No other units of measurement are included in this standard.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices
4、and determine the applicability of regulatorylimitations prior to use.WarningFresh hydraulic-cementitious mixtures are caustic and may cause chemical burns to skin and tissue upon prolongedexposure. The use of gloves, protective clothing, and eye protection is recommended. Wash contact area with cop
5、ious amounts ofwater after contact. Wash eyes for a minimum of 15 min. Avoid exposure of the body to clothing saturated with the liquid phaseof the unhardened material. Remove contaminated clothing immediately after exposure.1.3 This standard does not purport to address all of the safety concerns, i
6、f any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.Warning: Fresh hydraulic-cementitious mixtures are caustic and may cause chemical burns to s
7、kin and tissue upon prolongedexposure.21.4 The text of this standard references notes and footnotes which provide explanatory material. These notes and footnotes(excluding those in tables and figures) shall not be considered as requirements of the standard.2. Referenced Documents2.1 ASTM Standards:3
8、C150 Specification for Portland CementC183 Practice for Sampling and the Amount of Testing of Hydraulic CementC187 Test Method for Amount of Water Required for Normal Consistency of Hydraulic Cement PasteC219 Terminology Relating to Hydraulic CementC305 Practice for Mechanical Mixing of Hydraulic Ce
9、ment Pastes and Mortars of Plastic ConsistencyC670 Practice for Preparing Precision and Bias Statements for Test Methods for Construction MaterialsC1005 Specification for Reference Masses and Devices for Determining Mass and Volume for Use in the Physical Testing ofHydraulic CementsD1193 Specificati
10、on for Reagent Water3. Terminology3.1 Definitions:3.1.1 early stiffening, nthe early development of stiffness in the working characteristics of a hydraulic-cement paste, mortar,or concrete; varieties include false set and flash set.3.1.2 false set, nthe early development of stiffness in the working
11、characteristics of a hydraulic-cement paste, mortar, orconcrete without the evolution of much heat, which stiffness can be dispelled and plasticity regained by further mixing withoutaddition of water; also known as “grab set,” “premature stiffening,” “ hesitation set,” and “rubber set.”1 This test m
12、ethod is under the jurisdiction of ASTM Committee C01 on Cement and is the direct responsibility of Subcommittee C01.30 on Time of Set.Current edition approved June 1, 2008Dec. 1, 2013. Published June 2008January 2014 Originally approved in 1960. Last previous edition approved in 20072008 asC451 07.
13、C451 08. DOI: 10.1520/C0451-08.10.1520/C0451-13.2 Section on Safety, Manual of Cement Testing, Annual Book of ASTM Standards, Vol 04.01.3 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume inf
14、ormation, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately
15、depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM Interna
16、tional, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.3 flash set, nthe early development of stiffness in the working characteristics of a hydraulic-cement paste, mortar, orconcrete, usually with the evolution of considerable heat, which stiffness cannot be
17、dispelled nor can the plasticity be regained byfurther mixing without addition of water; also known as “quick set.”3.1.4 Refer to Terminology C219 for definitions of other terms.4. Summary of Test Method4.1 A paste is prepared with the cement to be tested, using sufficient water to give a required i
18、nitial penetration as measuredby the Vicat apparatus at a stipulated time after completion of mixing. A second penetration, termed the final penetration, ismeasured at a later stipulated time. The ratio of final penetration to initial penetration is calculated as a percentage.5. Significance and Use
19、5.1 The purpose of this test method is to determine the degree to which a cement paste develops early stiffening or to establishwhether or not a cement complies with a specification limit on early stiffening.5.2 When used for establishing compliance with a specification limit, the specification requ
20、irement is customarily stated interms of the minimum allowable final penetration, in percent, calculated in accordance with the Calculation Section. When usedfor estimating the relative tendency of a cement to manifest early stiffening, additional information of value may be obtained ifthe remix pro
21、cedure described in the Procedure Section is employed. Under some conditions, a judgment may be made bycomparing the behavior in the initial test and in the remix procedure to differentiate a relatively less serious and less persistenttendency to early stiffening (false set) from one that is more pe
22、rsistent and, consequently, more serious (flash set).5.3 Severe false setting in a cement may cause difficulty from a placing and handling standpoint, but it is not likely to causedifficulties where concrete is mixed for a longer time than usual, as usually occurs in transit mixing, or where it is r
23、emixed priorto placing or transporting, as occurs in concrete pumping operations. It is most likely to be noticeable where concrete is mixedfor a short period of time in stationary mixers and transported to the forms in non-agitating equipment, such as on some pavingjobs, and when concrete is made i
24、n an on-site batch plant.5.4 Cements with severe false setting usually require slightly more water to produce the same consistency, which may beexpected to result in slightly lower strengths and increased drying shrinkage.5.5 Early stiffening resulting from false set is not likely to cause a cement
25、to fail the applicable time of setting requirement.5.6 Early stiffening resulting from flash set, depending on severity, can cause a cement to fail the applicable time of settingrequirement.6. Apparatus6.1 Vicat Apparatus, conforming to the requirements of Test Method C187.6.2 Flat Trowel, having a
26、sharpened straight-edged steel blade 100 to 150 mm in length. The edges when placed on a planesurface shall not depart from straightness by more than 1 mm.6.3 Mixer, Bowl, Paddle, and Scraper, conforming to the requirements of Practice C305.6.4 Glass Graduates, 200 or 250 ml capacity, conforming to
27、the requirements of Specification C1005.6.5 Masses and Mass Determining Devices, conforming to the requirements of Specification C1005. The devices fordetermining mass shall be evaluated for precision and accuracy at a total load of 1000 g.6.6 Conical Ring, made of a rigid, non-corroding, non-absorb
28、ernt material, having a height of 40 6 1 mm, an inside diameterat the bottom of 70 6 3 mm, and an inside diameter at the top of 60 6 3 mm (see Test Method C187, Fig. 1 item G).6.7 Plane Non-Absorptive Plate, 10065 mm square, of similar planeness, corrosivity, and absorptivity to that of glass (see T
29、estMethod C187, Fig. 1 item H).6.8 Inspect and document Section 6 apparatus conformance to the requirements of this test method at least every 2 12 years.7. Reagent7.1 Mixing WaterPotable water is satisfactory for routine tests. For all referee and cooperative tests, use reagent waterconforming to t
30、he requirements of Specification D1193 for Type III or Type IV grades of reagent water.8. Sampling8.1 When the test is part of acceptance testing, sample the cement in accordance with Practice C183.9. Conditioning9.1 Maintain the temperature of the room, dry materials, paddle, bowl, conical ring, an
31、d base plate at 23.0 6 3.0 C. Maintainthe temperature of the mixing water at 23.0 6 2.0 C.C451 1329.2 Maintain the relative humidity of the mixing room at not less than 50 %.10. Procedure10.1 Preparation of Cement PasteMix 500 g of cement with sufficient water to produce a paste with an initial pene
32、tration of32 6 4 mm using the following procedure.10.1.1 Place the dry paddle and the dry bowl in the mixing position in the mixer.10.1.2 Introduce the materials for a batch into the bowl and mix 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 w
33、ater and allow 30 s for the water to absorb.10.1.2.3 Start the mixer and mix at a slow speed (1406 5 r/min) for 30 s.10.1.2.4 Stop the mixer for 15 s, and during this time scrape down into the batch any paste that may have collected on the sidesof the bowl.10.1.2.5 Start the mixer at a medium speed
34、(285 610 r/min) and mix for 212 min.10.2 Molding Test SpecimensQuickly form the cement paste into a ball with gloved hands. Press the ball, resting in the palmof one hand, into the larger end of the conical ring held in the other hand, completely filling the ring with paste. Remove the excessat the
35、larger end by a single movement of the palm of the hand. Place the ring on its larger end on the non-absorptive plate andslice off the excess paste at the smaller end at the top of the ring by a single oblique stroke of a sharp-edged trowel held at a slightangle with the top of the ring. Smooth the
36、top of the specimen, if necessary, with one or two light touches of the pointed end ofthe trowel. During the operation of cutting and smoothing, take care not to compress the paste.10.3 Determination of Initial PenetrationSet the paste confined in the ring resting on the plate, H, under the rod, B,
37、Fig. 1of Test Method C187, about one third of the diameter from the edge, and bring the plunger end, C, in contact with the surface ofthe paste and the tightened setscrew, E. Then set the movable indicator, F, to the upper zero mark of the scale, and release the rodexactly 20 s after completion of t
38、he mixing. Keep the apparatus free of all vibrations during the penetration test. Consider the pasteto have proper consistency when the rod settles to a point 3264 mm below the original surface in 30 s after being released. Maketrial pastes with varying percentages of water until this consistency is
39、 obtained. This consistency is the initial penetration. Duringthe 30-s interval for the initial penetration, return the excess paste to the bowl and cover the bowl and mixing paddle with a lid.10.4 Determination of Final PenetrationAfter completion of the initial reading, remove the plunger from the
40、 paste, clean it,and reset the ring and plate in a new position. Perform this operation with as little disturbance as possible to the paste confinedin the Vicat ring. Then bring the plunger again in contact with the surface of the paste, tighten the setscrew, and set the movableindicator to the uppe
41、r zero mark of the scale. Release the plunger a second time 5 min610 s after completion of the mixing period,and determine the final penetration 30 s after the plunger is released.10.5 Determination of Remix PenetrationIf the penetrations determined by the foregoing procedure show the cement to best
42、iffening rapidly, at the option of the tester, obtain information as to the nature of the stiffening by testing as follows:10.5.1 After completing the measurement of the 5-min penetration, immediately return the paste in the ring to the bowl.10.5.2 Start the mixer, raise the bowl into mixing positio
43、n, and remix the contents of the bowl at a medium speed (285 610r/min) for 1 min.10.5.3 Fill the ring and determine the penetration following the procedures specified in 10.2 and 10.3.11. Calculation11.1 Calculate the percent final penetration, based on the ratio of final penetration to initial pene
44、tration, as follows:P,%5BA 3100 (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 _ mmFinal penetration _ mmPercent final penetration _ %Remix penetration _ mm13. Precision and
45、 Bias13.1 PrecisionC451 13313.1.1 On samples testing between 8 % and 89 % Paste False Set, the single-operator (within laboratory) standard deviation hasbeen found to be 10 % (1s), therefore, results of two properly conducted tests by the same operator on samples of the same cementshould not differ
46、from each other by more than 28 % (1s and d2s are defined in Practice C670).13.1.2 On samples testing between 8 % and 89 % Paste False Set, the multi-laboratory standard deviation has been found to be12 % (1s), therefore, results of two properly conducted tests from two different laboratories on sam
47、ples of the same cement shouldnot differ by more than 34 % (1s and d2s are defined in Practice C670). (See Note 1.)13.2 Bias13.2.1 Since an acceptable reference material suitable for determining any bias of this method does not exist, no statement onbias is being made.NOTE 1This data is based upon C
48、CRL Portland Cement round robin test samples 47 to 138. The data indicates that precision decreases as the falseset values fall below approximately 60 %. These decreases are not clearly statistically significant, however they do indicate the duplication difficultieson cements which exhibit false set
49、 tendencies severe enough to fail or possibly fail Specification C150 optional limits.14. Keywords14.1 early stiffening; false set; flash set; hydraulic-cement paste; Vicat.VicatSUMMARY OF CHANGESCommittee C01 has identified the location of selected changes to this test method since the last issue,C451 07C451 08, that may impact the use of this test method. (Approved Dec. 1, 2013June 1, 2008)(1) Revised 6.2, 6.5, and 9.2.(1) Revised warning statement in 1.3.Committee C01 has identified the location of selected changes to this test method since the l
