ASTM C457-08a
Standard Test Method for Microscopical Determination of Parameters of the Air-Void System in Hardened Concrete
- Standard No.
- ASTM C457-08a
- Release Date
- 2008
- Published By
- American Society for Testing and Materials (ASTM)
- Status
- Replace By
- ASTM C457-08b
- Latest
- ASTM C457/C457M-23a
- Scope
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.
For air-entrained concrete designed in accordance with ACI 201.2R and ACI 211.1, the paste-air ratio (p/A) is usually in the range 4 to 10, the specific surface (α) is usually in the range 24 to 43 mm− 1 (600 to 1100 in.−1), and the spacing factor (
) is usually in the range 0.1 to 0.2 mm (0.004 to 0.008 in.). The air-void content determined in accordance with this test method usually agrees closely with the value determined on the fresh concrete in accordance with Test Methods C 138
, C 173 , or C 231 (11). However, significant differences may be observed if the sample of fresh concrete is consolidated to a different degree than the sample later examined microscopically. For concrete with a relatively high air content (usually over 7.5 %), the value determined microscopically may be higher by one or more percentage points than that determined by Test Method C 231 . 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 them. The ratio of the volume of aggregate to the volume of paste in the original mix must be accurately known or estimated to permit the calculation of the air-void systems parameters from the microscopically determined paste-air ratio.
Of the parameters determined with this test method, the spacing factor (
) is generally regarded as the most significant indicator of the durability of the cement paste matrix to freezing and thawing exposure of the concrete. The maximum value of the spacing factor for moderate exposure of the concre.........
ASTM C457-08a history
- 2024 ASTM C457/C457M-23a Standard Test Method for Microscopical Determination of Parameters of the Air-Void System in Hardened Concrete
- 2023 ASTM C457/C457M-23 Standard Test Method for Microscopical Determination of Parameters of the Air-Void System in Hardened Concrete
- 2016 ASTM C457/C457M-16 Standard Test Method for Microscopical Determination of Parameters of the Air-Void System in Hardened Concrete
- 2012 ASTM C457/C457M-12 Standard Test Method for Microscopical Determination of Parameters of the Air-Void System in Hardened Concrete
- 2011 ASTM C457/C457M-11 Standard Test Method for Microscopical Determination of Parameters of the Air-Void System in Hardened Concrete
- 2010 ASTM C457/C457M-10a Standard Test Method for Microscopical Determination of Parameters of the Air-Void System in Hardened Concrete
- 2010 ASTM C457/C457M-10 Standard Test Method for Microscopical Determination of Parameters of the Air-Void System in Hardened Concrete
- 2009 ASTM C457-09 Standard Test Method for Microscopical Determination of Parameters of the Air-Void System in Hardened Concrete
- 2008 ASTM C457-08d Standard Test Method for Microscopical Determination of Parameters of the Air-Void System in Hardened Concrete
- 2008 ASTM C457-08c Standard Test Method for Microscopical Determination of Parameters of the Air-Void System in Hardened Concrete
- 2008 ASTM C457-08b Standard Test Method for Microscopical Determination of Parameters of the Air-Void System in Hardened Concrete
- 2008 ASTM C457-08a Standard Test Method for Microscopical Determination of Parameters of the Air-Void System in Hardened Concrete
- 2008 ASTM C457-08 Standard Test Method for Microscopical Determination of Parameters of the Air-Void System in Hardened Concrete
- 2006 ASTM C457-06 Standard Test Method for Microscopical Determination of Parameters of the Air-Void System in Hardened Concrete
- 1998 ASTM C457-98 Standard Test Method for Microscopical Determination of Parameters of the Air-Void System in Hardened Concrete