ASTM C451-07
(Test Method)Standard Test Method for Early Stiffening of Hydraulic Cement (Paste Method)
Standard Test Method for Early Stiffening of Hydraulic Cement (Paste Method)
SIGNIFICANCE AND USE
The purpose of this test method is to determine the degree to which a cement paste develops early stiffening or to establish whether or not a cement complies with a specification limit on early stiffening.
When used for establishing compliance with a specification limit, the specification requirement is customarily stated in terms of the minimum allowable final penetration, in percent, calculated in accordance with the Calculation Section. 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 the Procedure Section 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, consequently, more serious (flash set).
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 where it is remixed prior to placing or transporting, as occurs in concrete pumping operations. It is most likely to be noticeable where concrete is mixed for a short period of time in stationary mixers and transported to the forms in non-agitating equipment, such as on some paving jobs, and when concrete is made in an on-site batch plant.
Cements with severe false setting usually require slightly more water to produce the same consistency, which may be expected to result in slightly lower strengths and increased drying shrinkage.
Early stiffening resulting from false set is not likely to cause a cement to fail the applicable time of setting requirement.
Early stiffening resulting from flash set, depending on severity, can cause a cement to fail the applicable time of setting requirement.
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 values given in parentheses are for information only.
This standard does not purport to address all of 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 regulatory limitations prior to use.
Warning-Fresh hydraulic-cementitious mixtures are caustic and may cause chemical burns to skin and tissue upon prolonged exposure. The use of gloves, protective clothing, and eye protection is recommended. Wash contact area with copious amounts of water after contact. Wash eyes for a minimum of 15 min. Avoid exposure of the body to clothing saturated with the liquid phase of the unhardened material. Remove contaminated clothing immediately after exposure.
1.3 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.
General Information
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Standards Content (Sample)
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Designation:C451–07
Standard Test Method for
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Early Stiffening of Hydraulic Cement (Paste Method)
This standard is issued under the fixed designation C 451; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope* C 670 Practice for Preparing Precision and Bias Statements
for Test Methods for Construction Materials
1.1 This test method covers the determination of early
C 1005 Specification for Reference Masses and Devices for
stiffening in hydraulic-cement paste.
Determining Mass and Volume for Use in the Physical
1.2 The values stated in SI units are to be regarded as the
Testing of Hydraulic Cements
standard. The values given in parentheses are for information
D 1193 Specification for Reagent Water
only.
1.3 This standard does not purport to address all of the
3. Terminology
safety concerns, if any, associated with its use. It is the
3.1 Definitions:
responsibility of the user of this standard to establish appro-
3.1.1 early stiffening, n—the early development of stiffness
priate safety and health practices and determine the applica-
in the working characteristics of a hydraulic-cement paste,
bility of regulatory limitations prior to use.
mortar, or concrete; varieties include false set and flash set.
Warning—Fresh hydraulic-cementitious mixtures are caus-
3.1.2 false set, n—the early development of stiffness in the
tic and may cause chemical burns to skin and tissue upon
working characteristics of a hydraulic-cement paste, mortar, or
prolonged exposure. The use of gloves, protective clothing,
concrete without the evolution of much heat, which stiffness
and eye protection is recommended. Wash contact area with
can be dispelled and plasticity regained by further mixing
copious amounts of water after contact. Wash eyes for a
without addition of water; also known as “grab set,” “prema-
minimum of 15 min. Avoid exposure of the body to clothing
ture stiffening,” “ hesitation set,” and “rubber set.”
saturated with the liquid phase of the unhardened material.
3.1.3 flash set, n—the early development of stiffness in the
Remove contaminated clothing immediately after exposure.
working characteristics of a hydraulic-cement paste, mortar, or
1.4 The text of this standard references notes and footnotes
concrete, usually with the evolution of considerable heat,
which provide explanatory material. These notes and footnotes
which stiffness cannot be dispelled nor can the plasticity be
(excluding those in tables and figures) shall not be considered
regained by further mixing without addition of water; also
as requirements of the standard.
known as “quick set.”
2. Referenced Documents 3.1.4 Refer to Terminology C 219 for definitions of other
2 terms.
2.1 ASTM Standards:
C 150 Specification for Portland Cement
4. Summary of Test Method
C 183 Practice for Sampling and the Amount of Testing of
4.1 A paste is prepared with the cement to be tested, using
Hydraulic Cement
sufficient water to give a required initial penetration as mea-
C 187 Test Method for Normal Consistency of Hydraulic
sured by the Vicat apparatus at a stipulated time after comple-
Cement
tion of mixing.Asecond penetration, termed the final penetra-
C 219 Terminology Relating to Hydraulic Cement
tion, is measured at a later stipulated time. The ratio of final
C 305 PracticeforMechanicalMixingofHydraulicCement
penetration to initial penetration is calculated as a percentage.
Pastes and Mortars of Plastic Consistency
5. Significance and Use
5.1 The purpose of this test method is to determine the
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This test method is under the jurisdiction ofASTM Committee C01 on Cement
degree to which a cement paste develops early stiffening or to
and is the direct responsibility of Subcommittee C01.30 on Time of Set.
establish whether or not a cement complies with a specification
Current edition approved July 15, 2007. Published August 2007. Originally
approved in 1960. Last previous edition approved in 2005 as C 451 – 05.
limit on early stiffening.
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For referenced ASTM standards, visit the ASTM website, www.astm.org, or
5.2 When used for establishing compliance with a specifi-
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
cation limit, the specification requirement is customarily stated
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. in terms of the minimum allowable final penetration, in
*A Summary of Changes section appears at the end of this standard.
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