1、Designation: C 451 07Standard 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 (e) 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
3、regarded as thestandard. The values given in parentheses are for informationonly.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 de
4、termine 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
5、amounts 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 explana
6、tory 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
7、Method 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 S
8、pecification 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
9、-cement 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
10、by 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 conside
11、rable 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, usingsu
12、fficient 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
13、as 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 specif
14、i-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 July 15
15、, 2007. Published August 2007. Originallyapproved in 1960. Last previous edition approved in 2005 as C 451 05.2For 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 st
16、andards 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 us
17、ed for 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 ther
18、emix 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
19、not likely 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 t
20、ime in 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
21、slightly 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
22、ofsetting 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.6.3 Mixer, Bowl, Paddle, and Scraper, conforming to therequirements of Practice C 305.6.4 Glass Graduates, 2
23、00 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 be evaluated for precision and bias at atotal load of 1000 g.6.6 Conical Ring, made of a
24、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).6.7 Plane Non-Absorptive Plate, 100 6 5 mm square, ofsimilar planeness, corrosivity, and abso
25、rptivity 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 WaterPotable water is satisfactory for routinetests. For all referee and cooperative tests, use
26、 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 with Practice C 183.9. Conditioning9.1 Maintain the temperature of the room, dry materials,pa
27、ddle, 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 laboratory at notless than 50 %.10. Procedure10.1 Preparation of Cement PasteMix 500 g of cementwith sufficient water to produce a paste wit
28、h 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 andmix in the following manner:10.1.2.1 Place all the mixing water in the bowl.10.1.2.2 Add th
29、e 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 batch any paste that may have collected on thesides of the bowl.10.1.2.5 Start the mixer at a
30、 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 the conical ring heldin the other hand, completely filling the ring with paste.Remove the exc
31、ess 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 single oblique stroke ofa sharp-edged trowel held at a slight angle with the top of thering. Smo
32、oth 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 of Initial PenetrationSet the pasteconfined in the ring resting on the plate, H, under the rod
33、, 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 indicator, F, to the upper zero mark of the scale, andrelease the rod exactly 20 s after completion
34、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 in30 s after being released. Make trial pastes with varyingpercentages of water until this consistency
35、 is obtained. Thisconsistency is the initial penetration. During the 30-s intervalC451072for the initial penetration, return the excess paste to the bowland cover the bowl and mixing paddle with a lid.10.4 Determination of Final PenetrationAfter completionof the initial reading, remove the plunger f
36、rom 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 incontact with the surface of the paste, tighten the setscrew, andset the movable indicator to the
37、 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 Remix PenetrationIf the penetra-tions determined by the foregoing procedure show the cementto
38、 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 return the paste in the ring to thebowl.10.5.2 Start the mixer, raise the bowl into mixing posit
39、ion,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 Calculate the percent final penetration, based on theratio of final penetration to initial penet
40、ration, 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 _ mmFinal penetration _ mmPercent final penetration _ %Remix penetration _ mm13. Precision and
41、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 conducted tests by the same operator on samplesof the same cement should not differ from each o
42、ther 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), therefore, results of two properlyconducted tests from two different laboratories on samples ofthe sa
43、me 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 does not exist, nostatement on bias is being made.NOTE 1This data is based upon CCRL Portland C
44、ement 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 they do indicate the duplicationdifficulties on cements which exhibit false set tendencies seve
45、re 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 location of selected changes to this test method since the last issue,C 451 05, that may impa
46、ct the use of this test method. (Approved July 15, 2007)(1) Added new 6.8.C451073ASTM 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 the va
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49、e 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).C451074
