1、Designation: C451 13C451 18Standard 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.Warning: Fresh hydraulic-cementitious mixtures are caustic and may cause chemical burns to skin and tissue upon prolongedexposure.21.4 The text of this standard references notes and footnotes which provide explanatory material. Th
5、ese notes and footnotes(excluding those in tables and figures) shall not be considered as requirements of the standard.1.5 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Developmen
6、t of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:3C150C150/C150M Specification for Portland CementC183C183/C183M Practice for Sampling and the Amount of Testing of Hydr
7、aulic 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 Cement Pastes and Mortars of Plastic ConsistencyC670 Practice for Preparing Precision and Bias State
8、ments 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 Specification for Reagent Water3. Terminology3.1 Definitions:3.1.1 early stiffening, nthe early development o
9、f 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 characteristics of a hydraulic-cement paste, mortar, orconcrete without the evolution of much heat
10、, 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.”3.1.3 flash set, nthe early development of stiffness in the working characteristics of a hydraulic-cement paste
11、, mortar, orconcrete, usually with the evolution of considerable heat, which stiffness cannot be dispelled nor can the plasticity be regained byfurther mixing without addition of water; also known as “quick set.”1 This test method is under the jurisdiction of ASTM Committee C01 on Cement and is the
12、direct responsibility of Subcommittee C01.30 on Time of Set.Current edition approved Dec. 1, 2013Oct. 1, 2018. Published January 2014.October 2018. Originally approved in 1960. Last previous edition approved in 20082013 asC451 08.C451 13. DOI: 10.1520/C0451-13.10.1520/C0451-18.2 Section on Safety, M
13、anual 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 information, refer to the standards Document Summary page on the ASTM web
14、site.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 depict all changes accurately, ASTM recommends that users consult prio
15、r 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 International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 1942
16、8-2959. United States13.1.4 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 initial penetration as measuredby the Vicat apparatus at a stipulated time after completion of
17、 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 Use5.1 The purpose of this test method is to determine the degree to which a cement paste develo
18、ps 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 requirement is customarily stated interms of the minimum allowable final penetration, in percent,
19、 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 procedure described in the Procedure Section is employed. Under some conditions, a judgment may
20、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 persistent and, consequently, more serious (flash set).5.3 Severe false setting in a cement may
21、 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 remixed priorto placing or transporting, as occurs in concrete pumping operations. It is most
22、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 in an on-site batch plant.5.4 Cements with severe false setting usually require slightly more
23、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 to fail the applicable time of setting requirement.5.6 Early stiffening resulting from flash
24、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 sharpened straight-edged steel blade 100 to 150 mm in length. The edges when placed on a plan
25、esurface shall not depart from straightness by more than 1 mm.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 the requirements of Specification C1005.6.5 Masses and Mass Determining Devices, conform
26、ing to the requirements of Specification C1005. The devices fordetermining mass shall be evaluated for precision and accuracy at continuing precise performance utilizing the procedure inSpecification C1005a total load of 1000 g., Appendix X1 using a verification check mass of approximately 1000 g.6.
27、6 Conical Ring, made of a rigid, non-corroding, non-absorbernt 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 planen
28、ess, corrosivity, and absorptivity to that of glass (see TestMethod C187, Fig. 1 item H).6.8 Inspect and document Section 6 apparatus conformance to the requirements of this test method at least every 212 years12 years.(see Note 1).NOTE 1Specification C1005 requires annual compliance checks for the
29、reference masses and for the devices for determining mass.7. Reagent7.1 Mixing WaterPotable water is satisfactory for routine tests. For all referee and cooperative tests, use reagent waterconforming to the requirements of Specification D1193 for Type III or Type IV grades of reagent water.8. Sampli
30、ng8.1 When the test is part of acceptance testing, sample the cement in accordance with Practice C183C183/C183M.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. 3.0C.Maintain the temperature of the mixing water at 23.
31、0 6 2.0 C. 2.0C.C451 1829.2 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 penetration of32 6 4 mm using the following procedure.10.1.1 Place the dry pad
32、dle 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 water and allow 30 s for the water to absorb.10.1.2.3 Start the mixer and m
33、ix at a slow speed (1406 55 r r/min) 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 (285 610 r/min) and mix for 212 min.10.2 Molding Test SpecimensQui
34、ckly 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 larger end by a single movement of the palm of the hand. Place the
35、 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 top of the specimen, if necessary, with one or two light touches o
36、f 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, Fig. 1of Test Method C187, about one third of the diameter from th
37、e 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 the mixing. Keep the apparatus free of all vibrations during the pe
38、netration 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 obtained. This consistency is the initial penetration. Duringthe
39、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 paste, clean it,and reset the ring and plate in a new position. P
40、erform 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 upper zero mark of the scale. Release the plunger a second time 5 min6
41、10 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 bestiffening rapidly, at the option of the tester, obtain information
42、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 position, and remix the contents of the bowl at a medium speed (285 6106
43、10 r/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 penetration, as follows:P,%5BA 3100 (1)where:P = percent final pe
44、netration,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 Bias13.1 PrecisionC451 18313.1.1 On samples testing between
45、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 from each other by more than 28 % (1s and d2s are defined in
46、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 samples of the same cement shouldnot differ by more than 34 % (1
47、s and d2s are defined in Practice C670). (See Note 12.)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 2This data is based upon CCRL Portland Cement round robin test samples 47 to 138. The
48、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 tendencies severe enough to fail or possibly fail Specifica
49、tion C150C150/C150M optional limits.14. Keywords14.1 early stiffening; false set; flash set; hydraulic-cement paste; VicatSUMMARY OF CHANGESCommittee C01 has identified the location of selected changes to this standard since the last issue (C451 13)that may impact the use of this standard. (Approved Oct. 1, 2018.)(1) Revised 6.5 and 6.8.(2) Added new Note 1 and renumbered subsequent notes accordingly.SUMMARY OF CHANGESCommittee C01 has identified the location of selected changes to this test method since the last issue,C451 08, that may impact th
