ASTM C457/C457M-11

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.

General Information

• Status: Historical
• Publication Date: 30-Sep-2011
• ICS: 91.100.30 - Concrete and concrete products
• Technical Committee: C09 - Concrete and Concrete Aggregates
• Drafting Committee: C09.65 - Petrography

Relations

• Replaces: ASTM C457/C457M-10a - Standard Test Method for Microscopical Determination of Parameters of the Air-Void System in Hardened Concrete
• Effective Date: 01-Oct-2011
• Referred By: ASTM C1709-22 - Standard Guide for Evaluation of Alternative Supplementary Cementitious Materials (ASCM) for Use in Concrete
• Effective Date: 01-Oct-2011
• Referred By: ASTM C1723-16(2022) - Standard Guide for Examination of Hardened Concrete Using Scanning Electron Microscopy
• Effective Date: 01-Oct-2011
• Referred By: ASTM C1140/C1140M-11(2019) - Standard Practice for Preparing and Testing Specimens from Shotcrete Test Panels
• Effective Date: 01-Oct-2011
• Referred By: ASTM C1324-20a - Standard Test Method for Examination and Analysis of Hardened Masonry Mortar
• Effective Date: 01-Oct-2011

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: C457/C457M − 11
StandardTest 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* 2. Referenced Documents
3
1.1 Thistestmethoddescribesproceduresformicroscopical 2.1 ASTM Standards:
determinations of the air content of hardened concrete and of C42/C42MTest Method for Obtaining and Testing Drilled
the specific surface, void frequency, spacing factor, and paste- Cores and Sawed Beams of Concrete
2
air ratio of the air-void system in hardened concrete (1). Two C125Terminology Relating to Concrete and Concrete Ag-
procedures are described: gregates
1.1.1 Procedure A, the linear-traverse method (2, 3). C138/C138MTestMethodforDensity(UnitWeight),Yield,
1.1.2 ProcedureB,themodifiedpoint-countmethod (3, 4, 5, and Air Content (Gravimetric) of Concrete
C173/C173MTestMethodforAirContentofFreshlyMixed
6).
Concrete by the Volumetric Method
1.2 This test method is based on prescribed procedures that
C231Test Method for Air Content of Freshly Mixed Con-
are applied to sawed and lapped sections of specimens of
crete by the Pressure Method
concrete from the field or laboratory.
C666/C666MTest Method for Resistance of Concrete to
1.3 Itisintendedtooutlinetheprinciplesofthistestmethod
Rapid Freezing and Thawing
and to establish standards for its adequate performance but not
C670Practice for Preparing Precision and Bias Statements
to describe in detail all the possible variations that might be
for Test Methods for Construction Materials
used to accomplish the objectives of this test method.
C672/C672MTest Method for Scaling Resistance of Con-
crete Surfaces Exposed to Deicing Chemicals
1.4 The values stated in either SI units or inch-pound units
C823Practice for Examination and Sampling of Hardened
are to be regarded separately as standard. The values stated in
each system may not be exact equivalents; therefore, each Concrete in Constructions
C856Practice for Petrographic Examination of Hardened
system shall be used independently of the other. Combining
values from the two systems may result in non-conformance Concrete
D92Test Method for Flash and Fire Points by Cleveland
with the standard.
Open Cup Tester
1.5 This standard does not purport to address all of the
2.2 American Concrete Institute Standards:
safety concerns associated with its use. It is the responsibility
4
201.2RGuide to Durable Concrete
of the user of this standard to establish appropriate safety and
211.1Recommended Practice for Selecting Proportions for
health practices and determine the applicability of regulatory
4
Normal, Heavyweight, and Mass Concrete
limitations prior to use. For specific hazard statements see 8.3
and 10.1.
3. Terminology
3.1 Fordefinitionsoftermsusedinthistestmethod,referto
Terminology C125.
1
This test method is under the jurisdiction of ASTM Committee C09 on
Concrete and ConcreteAggregatesand is the direct responsibility of Subcommittee
3
C09.65 on Petrography. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Oct. 1, 2011. Published November 2011. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 1960. Last previous edition approved in 2010 as C457/C457M–10a. Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/C0457_C0457M-11. the ASTM website.
2 4
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof AvailablefromAmericanConcreteInstitute(ACI),P.O.Box9094,Farmington
this test method. 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
1

---------------------- Page: 1 ----------------------
C457/C457M − 11
3.2 Definitions of Terms Specific to This Standard: number of stops in paste (S ), and the number of air voids (N)
p
¯
intersected by the line of traverse over which the component
3.2.1 average chord length ~l!,n—theaveragelengthofthe
data is gathered. From these data the air content and various
chords formed by the transection of the voids by the line of
parameters of the air-void system are calculated. If only the air
traverse; the unit is a length.
content is desired, only S and S need be determined.
a t
3.2.2 paste-air ratio (p/A), n—the ratio of the volume of
hardened cement paste to the volume of the air voids in the
4.3 Pas
...