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 Modified Point Count: Areas that are scratched or imperfect indicate the need for additional preparation; use special techniques if required see 8. 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 usual cause is a weak cement-paste matrix.
Additionally, this test method can be used for concrete product and mixture development requiring resistance of the concrete against freezing and thawing damage.
To convert to units of percent air content, divide by qstm and multiply by to get percent. Concrete and Concrete Aggregates and is the direct responsibility of Subcommittee C NOTE 1—The air-void content determined in accordance with this test.
They occur also immediately below surfaces that were compacted by finishing operations before the completion of bleeding. For specific hazard statements see Note 9 and Note This standard is subject to revision at any time by the responsible v457 committee and must be asmt every five years and if not revised, either reapproved or withdrawn.
If scaling and suspected freeze-thaw distress is the issue, or if delamination is the suspected problem, the samples need to contain the finished top surface. The maximum value of the spacing factor for moderate exposure of the concrete is usually taken to be 0.
The procedure followed and the location from which the samples are obtained will depend on the objectives of the program. ASTM C, petrographic examination of concrete.
ASTM C457.C457M – 12 – Microscopical Determination of Parameters of the Air-Void…
For concrete with a relatively high air content usually over 7. Referenced Documents purchase separately The documents listed below are referenced within the subject standard but are not provided as part of the standard. The problem is manifested by the plucking of sand grains from the surface during the lapping, with consequent scratching of the surface, and by undercutting of the paste around the harder aggregate particles. Juliano row Enviado por: Combining values from the two systems may result in non-conformance with the standard.
Juliano row Enviado por: Thus, this method can be used to evaluate the potential for damage due to cyclic freezing and thawing of the concrete.
These data are used to calculate the air content and various parameters of the air-void system. Spread the selected traverse length uniformly over the available surface so as to compensate for the heterogeneity of the concrete. No further reproductions authorized. Work Item s – proposed revisions of this standard. 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.
The data gathered are the linear distance between stops along the traverse Ithe total number of stops Stthe number of stops in air voids Sathe 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. They are significant only in mixtures that contained excessive mixing water or in which pronounced bleeding and settlement occurred.
Any such distinction is arbitrary, because the various types of voids intergrade in size, shape, and other characteristics. BoxSstm Hills, MIhttp: For voids per in.: Warning—If the specimen was sawn with a lubricant other than water, heating must be done so as to avoid inhaling the fumes and to preclude fire or explosion. Individual sections should be as large as can be ground and examined with the available equipment.
The factors affecting the variability of the test method are discussed in the section on Precision and Bias. It is the responsibility of the user of this standard to establish appropriate safety asrm health practices and determine the applicability of regulatory limitations prior to use.
ASTM C Microscopical Determination of the Air-Void System | CTL Grp
Results can also be applied to other situations in which the air content of concrete is in question. NOTE 2—Apparatus for measurement of prepared samples is described in the two following procedures. They occur also immediately below surfaces that were compacted by finishing operations before the completion of bleeding. ProceedingsHighway Research Board, Vol 29,p.
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 most astj examples are concrete with large coarse aggregate and samples from the finished surface region, for both of which the examined sample consists of a disproportionately large amount of the mortar fraction.
ASTM CCM – 12 – Microscopical Determination of Parameters of the Air-Void
Consequently, utmost care must be taken in conducting either microscopical method to observe and record. The CTLGroup contacts can assist with questions about sample size and number of samples. 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.
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.
Parte 4 de 4 Originally approved in Reports that do make such a distinction typically define entrapped air voids as being larger than 1 m in at least one dimension being irregular in shape, or both. They are most common beneath horizontal reinforcing bars, pieces of coarse aggregate and as channelways along their sides.