1、Designation:C295/C295M11 Designation: C295/C295M 12Standard Guide forPetrographic Examination of Aggregates for Concrete1This standard is issued under the fixed designation C295/C295M; the number immediately following the designation indicates the yearof original adoption or, in the case of revision
2、, the year of last revision. A number in parentheses indicates the year of last reapproval.A superscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope*1.1 This guide outlines pr
3、ocedures for the petrographic examination of samples representative of materials proposed for use asaggregates in cementitious mixtures or as raw materials for use in production of such aggregates. This guide is based on Ref (1).21.2 This guide outlines the extent to which petrographic techniques sh
4、ould be used, the selection of properties that should belooked for, and the manner in which such techniques may be employed in the examination of samples of aggregates for concrete.1.3 The rock and mineral names given in Descriptive Nomenclature C294 should be used, insofar as they are appropriate,
5、inreports prepared in accordance with this guide.1.4 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in eachsystem may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values fro
6、m thetwo systems may result in non-conformance with the standard.1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the appl
7、icability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:3C33 Specification for Concrete AggregatesC117 Test Method for Materials Finer than 75-m (No. 200) Sieve in Mineral Aggregates by WashingC136 Test Method for Sieve Analysis of Fine and Coarse AggregatesC294 Des
8、criptive Nomenclature for Constituents of Concrete AggregatesC702 Practice for Reducing Samples of Aggregate to Testing SizeD75 Practice for Sampling AggregatesE11 Specification for Woven Wire Test Sieve Cloth and Test SievesE883 Guide for ReflectedLight Photomicrography3. Qualifications of Petrogra
9、phers3.1 All petrographic examinations of aggregate for use in concrete as described in this guide should be performed by apetrographer with at least 5 years experience in petrographic examination of concrete or concrete-making materials. Thepetrographer should have completed college-level course wo
10、rk pertaining to basic geology, mineralogy, petrography, and opticalmineralogy or have obtained equivalent knowledge through experience and on-the-job training. Completion of course work inconcrete materials is also advantageous. The petrographer should have experience evaluating the effects of aggr
11、egates on thephysical and chemical properties of hardened concrete. Identification of individual minerals in aggregate particles, classificationof rock types, and categorizing the physical and chemical properties of rocks and minerals should also be included in thepetrographers experience. The petro
12、grapher should have expertise to properly use the equipment and apparatus described inSection 6 and provide detailed interpretations of the petrographic examination. If the petrographer does not meet thesequalifications, the individual may perform such examinations under the technical direction of a
13、 full-time supervising petrographerwho meets these qualifications. A resume of the professional experience and education of the petrographer shall be available.3.1.1 Licensing, certification, or other accreditation by a governmental agency or other organization stating the individual is a1This guide
14、 is under the jurisdiction of ASTM Committee C09 on Concrete and Concrete Aggregates and is the direct responsibility of Subcommittee C09.65 onPetrography.Current edition approved JulyApril 1, 2011.2012. Published August 2011.May 2012. Originally approved in 1954. Last previous edition approved in 2
15、0082011 asC29508.C295/C295M11. DOI: 10.1520/C0295_C0295M-112.2The boldface numbers in parentheses refer to the list of references at the end of this standard.3For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at serviceastm.org. For Annual Book of
16、ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.1This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technicall
17、y possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this stand
18、ard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.professional geologist should not, by itself, constitute sufficient qualification for examination of aggregates for concrete.4. Summary of Method4.1 The specific procedures employed
19、in the petrographic examination of any sample will depend to a large extent on thepurpose of the examination and the nature of the sample. In most cases the examination will require the use of optical microscopy.Complete petrographic examinations for particular purposes and to investigate particular
20、 problems may require examination ofaggregates or of selected constituents by means of additional procedures, such as X-ray diffraction (XRD) analysis, differentialthermal analysis (DTA), infrared spectroscopy, or other scanning electron microscopy (SEM) energy-dispersive x-ray analysis(EDX). In som
21、e instances, such procedures are more rapid and more definitive than are microscopical methods.4.2 Identification of the constituents of a sample is usually a necessary step towards recognition of the properties that may beexpected to influence the behavior of the material in its intended use, but i
22、dentification is not an end in itself. The value of anypetrographic examination will depend to a large extent on the representativeness of the samples examined, the completeness andaccuracy of the information provided to the petrographer concerning the source and proposed use of the material, and th
23、epetrographers ability to correlate these data with the findings of the examination.4.3 This guide does not attempt to describe the techniques of petrographic work since it is assumed that the guide will be usedby persons who are qualified by education and experience to employ such techniques for th
24、e recognition of the characteristicproperties of rocks and minerals and to describe and classify the constituents of an aggregate sample. In some cases, thepetrographer will have had experience adequate to provide detailed interpretation of the results. In others, the interpretation willbe made in p
25、art by engineers or others qualified to relate the observations to the questions to be answered.5. Significance and Use5.1 Petrographic examinations are made for the following purposes:5.1.1 To determine the physical and chemical characteristics of the material that may be observed by petrographic m
26、ethods andthat have a bearing on the performance of the material in its intended use.5.1.2 To describe and classify the constituents of the sample,5.1.3 To determine the relative amounts of the constituents of the sample that are essential for proper evaluation of the samplewhen the constituents dif
27、fer significantly in properties that have a bearing on the performance of the material in its intended use,and5.1.4 To compare samples of aggregate from new sources with samples of aggregate from one or more sources, for which testdata or performance records are available.5.2 This guide may be used
28、by a petrographer employed directly by those for whom the examination is made. The employershould tell the petrographer, in as much detail as necessary, the purposes and objectives of the examination, the kind of informationneeded, and the extent of examination desired. Pertinent background informat
29、ion, including results of prior testing, should be madeavailable. The petrographers advice and judgment should be sought regarding the extent of the examination.5.3 This guide may form the basis for establishing arrangements between a purchaser of consulting petrographic service andthe petrographer.
30、 In such a case, the purchaser and the consultant should together determine the kind, extent, and objectives of theexamination and analyses to be made, and should record their agreement in writing. The agreement may stipulate specificdeterminations to be made, observations to be reported, funds to b
31、e obligated, or a combination of these or other conditions.5.4 Petrographic examination of aggregate considered for use in hydraulic-cement concrete is one aspect of the evaluation ofaggregate, but petrographic examination is also used for many other purposes. Petrographic examinations provide ident
32、ificationof types and varieties of rocks present in potential aggregates. However, as noted above, identification of every rock and mineralpresent in an aggregate source is not required.5.5 The petrographic examination should establish whether the aggregate contains chemically unstable minerals such
33、 as solublesulfates, unstable sulfides that may form sulfuric acid or create distress in concrete exposed to high temperatures during service,or volumetrically unstable materials such as smectites (formerly known as the montmorillonite-saponite group of minerals orswelling clays). Specifications may
34、 limit the quartz content of aggregates for use in concrete that may be subject to hightemperature (purposefully or accidentally) because of the conversion to beta-quartz at 573 C 1063 F, with accompanyingvolume increase.5.6 Petrographic examination should identify the portion of each coarse aggrega
35、te that is composed of weathered or otherwisealtered particles and the extent of that weathering or alteration, whether it is severe, moderate, or slight, and should determine theproportion of each rock type in each condition. If the concrete in which the aggregate may be used will be exposed to fre
36、ezingand thawing in a critically saturated condition, finely porous and highly weathered or otherwise altered rocks should be identifiedbecause they will be especially susceptible to damage by freezing and thawing and will cause the aggregate portion of the concreteto fail in freezing and thawing. T
37、his will ultimately destroy the concrete because such aggregates cannot be protected by adequatelyair-entrained mortar. Finely porous aggregates near the concrete surface are also likely to form popouts, which are blemishes onpavements and walls.5.7 Petrographic examinations may also be used to dete
38、rmine the proportions of cubic, spherical, ellipsoidal, pyramidal, tabular,flat, and elongated particles in an aggregate sample or samples. Flat, elongated, and thin chip-like particles in aggregate increasethe mixing water requirement and hence decrease concrete strength.C295/C295M 1225.8 Petrograp
39、hic examination should identify and call attention to potentially alkali-silica reactive and alkali-carbonate reactiveconstituents, determine such constituents quantitatively, and recommend additional tests to confirm or refute the presence insignificant amounts of aggregate constituents capable of
40、alkali reaction in concrete. See Specification C33. Alkali-silica reactiveconstituents found in aggregates include: opal, chalcedony, cristobalite, tridymite, highly strained quartz, microcrystalline quartz,volcanic glass, and synthetic siliceous glass. Aggregate materials containing these constitue
41、nts include: glassy to cryptocrystallineintermediate to acidic volcanic rocks, some argillites, phyllites, graywacke, gneiss, schist, gneissic granite, vein quartz, quartzite,sandstone, and chert. Criteria are available for identifying the minerals in the list above by their optical properties or by
42、 XRD(2),(3). Criteria are available for identifying rocks by their mineral composition and texture (4). Examination in both reflected andtransmitted light may be necessary to provide data for these identifications. X-ray microanalysis using energy-dispersive x-rayspectrometers with scanning electron
43、 microscopy (SEM/EDX) or wavelength-dispersive x-ray spectrometers in electronmicroprobes (EMPA/WDX) may provide useful information on the chemical composition of minerals and rocks. Potentiallydeleterious alkali-carbonate reactive rocks are usually calcareous dolomites or dolomitic limestones with
44、clayey insoluble residues.Some dolomites essentially free of clay and some very fine-grained limestones free of clay and with minor insoluble residue,mostly quartz, are also capable of some alkali-carbonate reactions, however, such reactions are not necessarily deleterious.5.9 Petrographic examinati
45、on may be directed specifically at the possible presence of contaminants in aggregates, such assynthetic glass, cinders, clinker, or coal ash, magnesium oxide, calcium oxide, or both, gypsum, soil, hydrocarbons, chemicals thatmay affect the setting behavior of concrete or the properties of the aggre
46、gate, animal excrement, plants or rotten vegetation, andany other contaminant that may prove undesirable in concrete.5.10 These objectives, for which this guide was prepared, will have been attained if those involved with the evaluation ofaggregate materials for use in concrete construction have rea
47、sonable assurance that the petrographic examination results whereverand whenever obtained may confidently be compared.6. Apparatus and Supplies6.1 The apparatus and supplies listed as follows comprise a selection that will permit the use of the procedures described in thisguide.All specific items li
48、sted have been used, in connection with the performance of petrographic examinations, by the proceduresdescribed herein; it is not, however, intended to imply that other items cannot be substituted to serve similar functions. Wheneverpossible the selection of particular apparatus and supplies should
49、 be left to the judgment of the petrographer who is to performthe work so that the items obtained will be those with the use of which the petrographer has the greatest experience and familiarity.The minimum equipment regarded as essential to the making of petrographic examinations of aggregate samples are those items,or equivalent apparatus or supplies that will serve the same purpose, that are indicated by asterisks in the lists given as follows.6.1.1 Apparatus and Supplies for Preparation of Specimens:6.1.1.1 Rock-Cutting Saw, * preferably with 350-mm 14-in. diameter or
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