ASTM C457 PDF
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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Your comments are invited either for revision of this standard or for additional standards and should be addressed to ASTM International Headquarters.
Any such distinction is arbitrary, because the various types of voids intergrade in size, shape, and asm characteristics. They occur also immediately below surfaces that were compacted by finishing operations before the completion of bleeding.
If scaling and suspected freeze-thaw distress is the issue, or if delamination is asym suspected problem, the samples need to contain the finished top surface. Somewhat asfm values may be adequate for mild exposure, and smaller ones may be required for severe exposure, especially if the concrete is in contact with deicing chemicals.
Combining values from the two systems may result in non-conformance with the standard. The problem is manifested by the plucking of sand grains from the surface during the lapping, with consequent scratching of the aetm, and by undercutting of the paste around the xstm aggregate particles.
The CTLGroup contacts can assist with questions about sample size and number of samples. In such instances the usual procedure must be changed, and the paste-air ratio modification must be used see 5. They are most common beneath horizontal reinforcing bars, pieces of coarse aggregate and as channelways along their sides.
A sample may be composed of any number of specimens. A watervoid is usually identified by its irregular shape or evidence that a channel or cavity has been created by bleed water trapped in the concrete at the time it hardened. The required area may consist of more than one prepared section.
ASTM CCM – 12 – Microscopical Determination of Parameters of the Air-Void
If only the air content is desired, only Sa and St need be determined. They are significant only in mixtures that contained excessive mixing water or in which pronounced bleeding and settlement occurred. Consequently, utmost care must be taken in conducting either microscopical method to observe and record. This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years and if not revised, either reapproved or withdrawn.
The data gathered are the total length traversed Ttthe length traversed through air voids Tathe length traversed through paste Tpand the number of air voids intersected by the traverse line N. For voids per in.: 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.
Individual reprints single or multiple copies of this standard may be obtained by contacting ASTM at the above address or at phonefaxor service astm. Three procedures are described:.
Originally approved in A surface that is satisfactory for microscopical examination will show an excellent reflection of a distant light source when viewed at a low incident angle and there shall be no noticeable relief between the paste and the aggregate surfaces.
Open Cup Tester 2. They occur also immediately below surfaces that c4457 compacted by finishing operations before the completion of bleeding. The usual cause is a weak cement-paste matrix. Hence, this test method can be used to develop data to estimate the likelihood astj damage due to cyclic freezing and thawing or to explain why it has occurred.
ASTM C457.C457M – 12 – Microscopical Determination of Parameters of the Air-Void…
Results 4c57 also be applied to asm situations in which the air content of concrete is in question. If you need more info or have any questions, please note the Lab ID number 56 and contact us at: The most common examples are concrete with large coarse aggregate and samples from the finished surface c47, for both of which the examined sample consists of a disproportionately large amount of the mortar fraction. Sample Type hardened concrete, mortar, other portland-cement-based materials.
NOTE 1—The air-void content determined in accordance with this test. If only the air content is desired, only Ta and Tt need be determined. 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.
The data gathered are the linear distance between stops along the traverse Ithe total number of stops Stthe number of stops in air voids Sa 4c57, the number of stops in paste Spand the number of air voids N intersected by the line of traverse over which the component data is gathered. From time to time during lapping, and when changing to a finer abrasive and when lapping is complete, clean sstm surfaces of the specimen gently and thoroughly to remove the grinding compound.
If you feel that your comments have not received a fair hearing you should make your views known to the ASTM Committee on Standards, at the address shown below.
To convert to units of percent air content, divide by n and multiply by to get percent. The parameters determined by this procedure are most often related to the susceptibility of the concrete to freezing and thawing damage. 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. 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.
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.
However, significant differences may be observed if the sample of fresh concrete is consolidated to a different degree than the specimen later examined microscopically. 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. Because Procedure C requires darkening the paste and aggregate, its use must occur after other tests if the analyst is also gathering petrographic data in addition to the measurements described in this test method.
Paste content determinations were made by 13 operators representing 8 different laboratories. Appraisal, John Wiley and Sons, Inc. Cleaning with a soft cosmetic brush under running water, or by a pressurized dental spray has been successful.
Eleven were by point count and 2 by linear traverse procedures.