1、Standard Method of Test for Early Stiffening of Hydraulic Cement (Paste Method) AASHTO Designation: T 186-151ASTM Designation: C451-13 American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-3a T 186-1 AASHTO Standard Meth
2、od of Test for Early Stiffening of Hydraulic Cement (Paste Method) AASHTO Designation: T 186-151ASTM Designation: C451-13 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 to be regarded as the standard. The
3、values given in parentheses are for information only. 1.3. This standard does not purport to address all the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of
4、 regulatory limitations prior to use. WarningFresh hydraulic-cementitious mixtures are caustic and may cause chemical burns to skin and tissue upon prolonged exposure. 1.4. The text of this standard references notes and footnotes that provide explanatory material. These notes and footnotes (excludin
5、g those in tables and figures) shall not be considered as requirements of the standard. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: R 71, Sampling and Amount of Testing of Hydraulic Cement T 129, Amount of Water Required for Normal Consistency of Hydraulic Cement Paste T 162, Mechanical Mixing of
6、 Hydraulic Cement Pastes and Mortars of Plastic Consistency 2.2. ASTM Standards: C219, Standard Terminology Relating to Hydraulic Cement C670, Standard Practice for Preparing Precision and Bias Statements for Test Methods for Construction Materials C1005, Standard Specification for Reference Masses
7、and Devices for Determining Mass and Volume for Use in the Physical Testing of Hydraulic Cements D1193, Standard Specification for Reagent Water 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3a T 18
8、6-2 AASHTO 2.3. NCHRP Report: Azari, H. and R. Lutz. NCHRP Web-Only Document 140: Precision Estimates for AASHTO Test Methods T 186, T 154, and T 22, Determined Using CCRL Proficiency Sample Data. National Cooperative Highway Research Program (NCHRP), Transportation Research Board of the National Ac
9、ademies, Washington, DC, 2009, 48 pp. http:/onlinepubs.trb.org/onlinepubs/nchrp/nchrp_w140.pdf 3. TERMINOLOGY 3.1. 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 an
10、d flash set. 3.1.2. false set, nthe early development of stiffness in the working characteristics of a hydraulic cement paste, mortar, or concrete without the evolution of much heat. This stiffness can be dispelled and plasticity regained by further mixing without addition of water. Also known as “g
11、rab 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, mortar, or concrete, usually with the evolution of considerable heat. This stiffness cannot be dispelled nor can the
12、 plasticity be regained by further mixing without addition of water. Also known as “quick set.” 3.1.4. Refer to ASTM C219 for definitions of other terms. 4. SUMMARY OF TEST METHOD 4.1. A paste is prepared with the cement to be tested, using sufficient water to give a required initial penetration as
13、measured by the Vicat apparatus at a stipulated time after completion of mixing. A second penetration, termed the “final penetration,” is measured at a later stipulated time. The ratio of final penetration to initial penetration is calculated as a percentage. 5. SIGNIFICANCE AND USE 5.1. The purpose
14、 of this test method is to determine the degree to which a cement paste develops early stiffening or establish whether 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
15、 stated in terms of the minimum allowable final penetration, in percent, calculated in accordance with Section 11, Calculation. When used for estimating the relative tendency of a cement to manifest early stiffening, additional information of value may be obtained if the remix procedure described in
16、 Section 10, Procedure, is employed. Under some conditions, a judgment may be made by comparing the behavior in the initial test and in the remix procedure to differentiate a relatively less serious and less persistent tendency to early stiffening (false set) from one that is more persistent and, co
17、nsequently, 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 cause difficulties where concrete is mixed for a longer time than usual, as usually occurs in transit mixing, or when it is remixed prior t
18、o placing or transporting, as occurs in concrete pumping operations. It is most likely to be noticeable when concrete is mixed for a short 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3a T 186-3 AA
19、SHTO period of time in stationary mixers and transported to the forms in nonagitating equipment, such as on some paving jobs, and when concrete is made in an on-site batch plant. 5.4. Cements with severe false setting usually require slightly more water to produce the same consistency, which may be
20、expected 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 set, depending on severity, can cause a cement
21、to fail the applicable time of setting requirement. 6. APPARATUS 6.1. Vicat ApparatusConforming to the requirements of T 129. 6.2. Flat TrowelHaving a sharpened straight-edge steel blade 100 to 150 mm (4 to 6 in.) in length. The edges when placed on plane surface shall not depart from straightness b
22、y more than 1 mm. 6.3. Mixer, Bowl, Paddle, and ScraperConforming to the requirements of T 162. 6.4. Glass Graduates200- or 250-mL capacity, conforming to the requirements of ASTM C1005. 6.5. Masses and Mass Determining DevicesConforming to the requirements of ASTM C1005. The devices for determining
23、 mass shall be evaluated for precision and accuracy at a total load of 1000 g. 6.6. Conical RingMade of rigid, noncorroding, nonabsorbent material, having a height of 40 1 mm, an inside diameter at the bottom of 70 3 mm, and an inside diameter at the top of 60 3 mm (see T 129, Figure 1, G). 6.7. Pla
24、ne Nonabsorptive Plate100 5 mm square, of similar planeness, corrosivity, and absorptivity to that of glass (see T 129, Figure 1, H). 6.8. Inspect and document Section 6 apparatus for conformance to the requirements of this test method at least every 21/2years. 7. REAGENTS 7.1. Mixing WaterPotable w
25、ater is satisfactory for routine tests. For all referee and cooperative tests, use reagent water conforming to the requirements of ASTM D1193 for Type III or Type IV grades of reagent water. 8. SAMPLING 8.1. When the test is part of acceptance testing, sample the cement in accordance with R 71. 2016
26、 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3a T 186-4 AASHTO 9. CONDITIONING 9.1. Maintain the temperature of the room, dry materials, paddle, bowl, conical ring, and base plate at 23.0 3.0C. Maintai
27、n the temperature of the mixing water at 23.0 2.0C. 9.2. Maintain the relative humidity of the mixing room at no less than 50 percent. 10. PROCEDURE 10.1. Preparation of Cement PasteMix 500 g of cement with sufficient water to produce a paste with an initial penetration of 32 4 mm using the followin
28、g 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 water and allow 30 s for the wa
29、ter to absorb. 10.1.2.3. Start the mixer and mix at slow speed (140 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 sides of the bowl. 10.1.2.5. Start the mixer at medium speed (285 10 r/min) and mix for
30、 21/2min. 10.2. Molding Test SpecimensQuickly form the cement paste into a ball with gloved hands. Press the ball, resting in the palm of one hand, into the larger end of the conical ring held in the other hand, completely filling the ring with paste. Remove the excess at the larger end by a single
31、movement of the palm of the hand. Place the ring on its larger end on the nonabsorptive plate, H, and slice 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 slight angle with the top of the ring. Smooth the top of the specime
32、n, if necessary, with one or two light touches of the pointed end of the 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, Figure 1 of T 1
33、29, about one-third of the diameter from the edge, and bring the plunger end, C, in contact with the surface of the paste and the tightened set screw, E. Then set the movable indicator, F, to the upper zero mark of the scale, and release the rod exactly 20 s after completion of the mixing. Keep the
34、apparatus free of all vibrations during the penetration test. Consider the paste to have proper consistency when the rod settles to a point 32 4 mm below the original surface in 30 s after being released. Make trial pastes with varying percentages of water until this consistency is obtained. This co
35、nsistency is the initial penetration. During the 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 i
36、t, and reset the ring and plate in a new position. Perform this operation with as little disturbance as possible to the paste confined in the Vicat ring. Then bring the plunger again in contact with the surface of the paste, tighten the set screw, and set the movable indicator to the upper zero mark
37、 of the scale. Release the plunger a second time 5 min (10 s) after completion of the mixing period, and determine the final penetration 30 s after the plunger is released. 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation
38、of applicable law.TS-3a T 186-5 AASHTO 10.5. Determination of Remix PenetrationIf the penetrations determined by the foregoing procedure show the cement to be stiffening rapidly, at the option of the tester, obtain information as to the nature of the stiffening by testing as follows: 10.5.1. After c
39、ompleting 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 medium speed (285 10 r/min) for 60 s. 10.5.3. Fill the ring and determine the penetration foll
40、owing the procedures specified in Sections 10.2 and 10.3. 11. CALCULATION 11.1. Calculate the percent final penetration, based on the ratio of final penetration to initial penetration, as follows: , % 100BPA= (1) where: P = percent final penetration; B = final penetration, mm; and A = initial penetr
41、ation, mm. 12. REPORT 12.1. Report the results of the test as follows in Table 1: Table 1Early Stiffening Report Initial penetration _ mm Final penetration _ mm Percent final penetration _ % Remix penetration _ mm 13. PRECISION AND BIAS 13.1. Precision: 13.1.1. Single-Operator PrecisionThe single-op
42、erator standard deviations (1s limits) for percent Paste False Set of hydraulic cement are shown in Table 2. The results of two properly conducted tests on the same material, by the same operator, using the same equipment, should be considered suspect if they differ by more than d2s single-operator
43、limits shown in Table 2. 13.1.2. Multilaboratory PrecisionThe multilaboratory standard deviations (1s limits) for percent Paste False Set of hydraulic cement are shown in Table 2. The results of two properly conducted tests on the same material, by different operators, using different equipment, sho
44、uld be considered suspect if they differ by more than d2s multilaboratory limits shown in Table 2. 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3a T 186-6 AASHTO Table 2Precision Estimates of Early
45、 Stiffening of Hydraulic Cement (Paste Method) Condition of Test and Test Property Standard Deviation (1s), %aAcceptable Range of Two Test Results (d2s), %aSingle-operator precision 7 21 Multilaboratory precision 8 24 Note: The precision estimates given in Table 2 are based on the analysis of test r
46、esults from six pairs of CCRL proficiency samples 147 to 162. The data analyzed consisted of results from 171 to 210 laboratories for each pair of samples. The analysis included cement pastes with average False Set of 69 percent to 85 percent. The details of this analysis are found in Web Document 1
47、40, prepared as part of Phase A of NCHRP Project 9-26. aThese values represent the 1s and d2s limits described in ASTM C670. 13.2. Bias: 13.2.1. No information can be presented on the bias of the procedure because no comparison with the material having an accepted reference value was conducted. 14.
48、KEYWORDS 14.1. Early stiffening; false set; flash set; hydraulic cement paste; Vicat. 1Except for the use of SI units, this method agrees with ASTM C451-13. 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.
