ASTM C457/C457M-10
(Test Method)Standard Test Method for Microscopical Determination of Parameters of the Air-Void System in Hardened Concrete
Standard Test Method for Microscopical Determination of Parameters of the Air-Void System in Hardened Concrete
SIGNIFICANCE AND USE
The parameters of the air-void system of hardened concrete determined by the procedures described in this test method are related to the susceptibility of the cement paste portion of the concrete to damage by freezing and thawing. Hence, this test method can be used to develop data to estimate the likelihood of damage due to cyclic freezing and thawing or to explain why it has occurred. The test method can also be used as an adjunct to the development of products or procedures intended to enhance the resistance of concrete to cyclic freezing and thawing (1).
Values for parameters of the air-void system can be obtained by either of the procedures described in this test method.
No provision is made for distinguishing among entrapped air voids, entrained air voids, and water voids. Any such distinction is arbitrary, because the various types of voids intergrade in size, shape, and other characteristics. Reports that do make such a distinction typically define entrapped air voids as being larger than 1 mm in at least one dimension being irregular in shape, or both. The honey-combing that is a consequence of the failure to compact the concrete properly is one type of entrapped air void (9, 10).
Water voids are cavities that were filled with water at the time of setting of the concrete. They are significant only in mixtures that contained excessive mixing water or in which pronounced bleeding and settlement occurred. They are most common beneath horizontal reinforcing bars, pieces of coarse aggregate and as channelways along their sides. They occur also immediately below surfaces that were compacted by finishing operations before the completion of bleeding.
Application of the paste-air ratio procedure is necessary when the concrete includes large nominal maximum size aggregate, such as 50 mm [2 in.] or more. Prepared sections of such concrete should include a maximum of the mortar fraction, so as to increase the number of counts on air voids or traverse across...
SCOPE
1.1 This test method describes procedures for microscopical determinations of the air content of hardened concrete and of the specific surface, void frequency, spacing factor, and paste-air ratio of the air-void system in hardened concrete (1). Two procedures are described:
1.1.1 Procedure A,
the linear-traverse method (2, 3).
1.1.2 Procedure B,
the modified point-count method (3, 4, 5, 6).
1.2 This test method is based on prescribed procedures that are applied to sawed and lapped sections of specimens of concrete from the field or laboratory.
1.3 It is intended to outline the principles of this test method and to establish standards for its adequate performance but not to describe in detail all the possible variations that might be used to accomplish the objectives of this test method.
1.4 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.
1.5 This standard does not purport to address all of the safety concerns 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. For specific hazard statements see 8.3 and 10.1.
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Standards Content (Sample)
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Designation: C457/C457M – 10
Standard Test Method for
Microscopical Determination of Parameters of the Air-Void
1
System in Hardened Concrete
This standard is issued under the fixed designation C457/C457M; the number immediately following the designation indicates the year
of original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.
A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope* C42/C42M Test Method for Obtaining and Testing Drilled
Cores and Sawed Beams of Concrete
1.1 Thistestmethoddescribesproceduresformicroscopical
C125 Terminology Relating to Concrete and Concrete Ag-
determinations of the air content of hardened concrete and of
gregates
the specific surface, void frequency, spacing factor, and paste-
2
C138/C138M Test Method for Density (Unit Weight),
air ratio of the air-void system in hardened concrete (1). Two
Yield, and Air Content (Gravimetric) of Concrete
procedures are described:
C173/C173M Test Method for Air Content of Freshly
1.1.1 Procedure A, the linear-traverse method (2, 3).
Mixed Concrete by the Volumetric Method
1.1.2 ProcedureB,themodifiedpoint-countmethod(3,4,5,
C231 Test Method for Air Content of Freshly Mixed Con-
6).
crete by the Pressure Method
1.2 This test method is based on prescribed procedures that
C666/C666M Test Method for Resistance of Concrete to
are applied to sawed and lapped sections of specimens of
Rapid Freezing and Thawing
concrete from the field or laboratory.
C670 Practice for Preparing Precision and Bias Statements
1.3 Itisintendedtooutlinetheprinciplesofthistestmethod
for Test Methods for Construction Materials
and to establish standards for its adequate performance but not
C672/C672M Test Method for Scaling Resistance of Con-
to describe in detail all the possible variations that might be
crete Surfaces Exposed to Deicing Chemicals
used to accomplish the objectives of this test method.
C823 Practice for Examination and Sampling of Hardened
1.4 The values stated in either SI units or inch-pound units
Concrete in Constructions
are to be regarded separately as standard. The values stated in
C856 Practice for Petrographic Examination of Hardened
each system may not be exact equivalents; therefore, each
Concrete
system shall be used independently of the other. Combining
D92 Test Method for Flash and Fire Points by Cleveland
values from the two systems may result in non-conformance
Open Cup Tester
with the standard.
2.2 American Concrete Institute Standards:
1.5 This standard does not purport to address all of the
4
201.2R Guide to Durable Concrete
safety concerns associated with its use. It is the responsibility
211.1 Recommended Practice for Selecting Proportions for
of the user of this standard to establish appropriate safety and
4
Normal, Heavyweight, and Mass Concrete
health practices and determine the applicability of regulatory
limitations prior to use. For specific hazard statements see 8.3
3. Terminology
and 10.1.
3.1 Fordefinitionsoftermsusedinthistestmethod,referto
2. Referenced Documents Terminology C125.
3
3.2 Definitions of Terms Specific to This Standard:
2.1 ASTM Standards:
3.2.1 average chord length ( l ), n—the average length of
thechordsformedbythetransectionofthevoidsbythelineof
1
This test method is under the jurisdiction of ASTM Committee C09 on
traverse; the unit is a length.
Concrete and ConcreteAggregates and is the direct responsibility of Subcommittee
3.2.2 paste-air ratio (p/A), n—the ratio of the volume of
C09.65 on Petrography.
hardened cement paste to the volume of the air voids in the
Current edition approved April 1, 2010. Published May 2010. Originally
approved in 1960. Last previous edition approved in 2009 as C457–09. DOI:
concrete.
10.1520/C0457_C0457M-10.
2
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
this test method.
3
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
4
Standards volume information, refer to the standard’s Document Summary page on AvailablefromAmericanConcreteInstitute(ACI),P.O.Box9094,Farmington
the ASTM website. Hills, MI 48333-9094, http://www.aci-int.org.
*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.
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C457/C457M – 10
3.2.3 paste content (p), n—the proportion of the total and S lose their significance and cannot be used as a basis for
t
volumeoftheconcretethatishardenedcementpasteexpressed calculations. The most common examples are concrete with
as percentage by volume. large coarse aggregate and samples from th
...
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