Baixe grátis o arquivo ASTM CCM – 12 _ Microscopical Determination of Parameters of the Air-Void System in Hardened Concrete (2).pdf enviado por. This standard is issued under the fixed designation C ; the number concrete. 1 This practice is under the jurisdiction of ASTM Committee C-9 on Concrete. Humboldt’s Linear Traverse Machine for concrete air void testing facilitates the counting of microscopic voids in concrete. Meets or exceeds ASTM C
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A Includes determinations using both point count and linear traverse. In all, 19 operators participated with a total of 41 determinations on each specimen.
Air Void Testing for Concrete, ASTM C
Paste content determinations were made by 13 operators representing 8 ast, laboratories. Eleven were by point count and 2 by linear traverse procedures. B These numbers represent, respectively, the 1s and D2s limits as described in Practice C A Includes all data—all labs and all operators. Includes both point count and linear traverse data.
ASTM C457.C457M – 12 – Microscopical Determination of Parameters of the Air-Void…
B Theoretical Standard Deviation: To convert to units of percent air content, divide by n and multiply by to get percent. For voids per in.: No further reproductions authorized.
The following text provides useful information on air-void system parameters of known freeze-thaw durable concrete and explains guidelines and specifications from other respected specifying agencies. The maximum value of the spacing factor for moderate exposure of the concrete is usually taken to be 0.
Somewhat larger values may be adequate for mild exposure, and smaller ones may be required for severe exposure, especially if the concrete is asfm contact with deicing chemicals. Care should be exercised in using spacing factor values in specifications since the standard deviation of that property has been found to approach one-fifth of the average when determinations are made in different laboratories.
Hence, substantial differences in spacing factor may be caused solely by sampling and f457 laboratory variation. The factors affecting the variability of the test method are discussed in the section on Precision and Bias. An increase in the water-cement ratio or the paste content must be accompanied by an increase in the air content, if the spacing factor.
Extended vibration is not, however, recommended as a field practice because of the dangers of excessive bleeding and segregation. Consequently, utmost care must be taken in conducting either microscopical method to observe and record. A These numbers represent, respectively, the 1s and D2s limits as described in Practice C A Modified Point Count: Such compressive strength must be at least 28 MPa [ psi].
ProceedingsHighway Research Board, Vol 29,p. Appraisal, John Wiley and Sons, Inc. Reviews in Engineering Geology, Geol.
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