ASTM_C_295_C295M-19.pdf

This international standard was developed in accordance with internationallygnized principles on standardization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade(TBT)Committee.Designation:C295/C295M-19NTERNATIONALStandard 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.the year of last revision.A number in parentheses indicates the year of last reapprovalA superscript epsilon(e)indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S.Department of Defense.1.Scope*2.Referenced Documents1.1 This guide outlines procedures for the petrographic2.1 ASTM Standards:3examination of samples representative of materials proposedC33/C33M Specification for Concrete Aggregatesfor use as aggregates in cementitious mixtures or as rawC117 Test Method for Materials Finer than 75-um(No.200)materials for use in production of such aggregates.This guideSieve in Mineral Aggregates by Washingis based on Ref(1).C136/C136M Test Method for Sieve Analysis of Fine andCoarse Aggregates1.2 This guide outlines the extent to which petrographicC294 Descriptive Nomenclature for Constituents of Con-techniques should be used,the selection of properties thatcrete Aggregatesshould be looked for,and the manner in which such techniquesC702/C702M Practice for Reducing Samples of Aggregatemay be employed in the examination of samples of aggregatesto Testing Sizefor concrete.D75/D75M Practice for Sampling Aggregates1.3 The rock and mineral names given in DescriptiveE11 Specification for Woven Wire Test Sieve Cloth and TestNomenclature C294 should be used,insofar as they areSievesappropriate,in reports prepared in accordance with this guide.E883 Guide for Reflected-Light Photomicrography1.4 The values stated in either SI units or inch-pound units3.Qualifications of Petrographersare to be regarded separately as standard.The values stated in3.1 All petrographic examinations of aggregate for use ineach system may not be exact equivalents;therefore,eachconcrete as described in this guide should be performed by asystem shall be used independently of the other.Combiningpetrographer with at least 5 years experience in petrographicvalues from the two systems may result in non-conformanceexamination of concrete or concrete-making materials.Thewith the standard.petrographer should have completed college-level course work1.5 This standard does not purport to address all of thepertaining to basic geology,mineralogy,petrography,andsafety concerns,if any,associated with its use.It is theoptical mineralogy or have obtained equivalent knowledgeresponsibility of the user of this standard to establish appro-through experience and on-the-job training.Completion ofpriate safery,health,and environmental practices and deter-course work in concrete materials is also advantageous.Themine the applicability of regulatory limitations prior to use.petrographer should have experience evaluating the effects of1.6 This international standard was developed in accor-aggregates on the physical and chemical properties of hardenedconcrete.Identification of individual minerals in aggregatedance with internationally recognized principles on standard-particles,classification of rock types,and categorizing theization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recom-physical and chemical properties of rocks and minerals shouldmendations issued by the World Trade Organization Technicalalso be included in the petrographers experience.The petrog-Barriers to Trade(TBT)Committee.rapher should have expertise to properly use the equipment andapparatus described in Section 6 and provide detailed interpre-tations of the petrographic examination.If the petrographerdoes not meet these qualifications,the individual may performI This guide is under the jurisdiction of ASTM Committee C09 on Concrete andsuch examinations under the technical direction of a full-timeConcrete Aggregates and is the direct responsibility of Subcommittee C09.65 onPetrography.Current edition approved Aug.1.2019.Published September 2019.Originallyapproved in 1954.Last previous edition approved in 2018 as C295/C295M-18a.3 For referenced ASTM standards,visit the ASTM website,www.astm.org.orD0:10.1520/C0295C0295M-19.contact ASTM Customer Service at serviceastm.org.For Annual Book of ASTM2 The boldface numbers in parentheses refer to the list of references at the end ofStandards volume information,refer to the standards Document Summary page onthis standard.the ASTM website.*A Summary of Changes section appears at the end of this standardCopyright ASTM Intemational,100 Barr Harbor Drive,PO Box C700.West Conshohocken.PA 19428-2959.United StatesC295/C295M-19supervising petrographer who meets these qualifications.A5.1.4 To compare samples of aggregate from new sourcesresume of the professional experience and education of thewith samples of aggregate from one or more sources,for whichpetrographer shall be available.test data or performance records are available.3.1.1 Licensing,certification,or other accreditation by a5.2 This guide may be used by a petrographer employedgovernmental agency or other organization stating the indi-directly by those for whom the examination is made.Thevidual is a professional geologist should not,by itself,consti-employer should tell the petrographer,in as much detail astute sufficient qualification for examination of aggregates fornecessary,the purposes and objectives of the examination,theconcrete.kind of information needed,and the extent of examination4.Summary of Methoddesired.Pertinent background information,including results ofprior testing,should be made available.The petrographers4.1 The specific procedures employed in the petrographicadvice and judgment should be sought regarding the extent ofexamination of any sample will depend to a large extent on thethe examination.purpose of the examination and the nature of the sample.Inmost cases the examination will require the use of optical5.3 This guide may form the basis for establishing arrange-microscopy.Complete petrographic examinations for particu-ments between a purchaser of consulting petrographic servicelar purposes and to investigate particular problems may requireand the petrographer.In such a case,the purchaser and theexamination of aggregates or of selected constituents by meansconsultant should together determine the kind,extent,andof additional procedures,such as X-ray diffraction(XRD)objectives of the examination and analyses to be made,andanalysis,differential thermal analysis(DTA),infraredshould record their agreement in writing.The agreement mayspectroscopy,or other scanning electron microscopy(SEM)stipulate specific determinations to be made,observations to beenergy-dispersive x-ray analysis(EDX).In some instances,reported,funds to be obligated,or a combination of these orsuch procedures are more rapid and more definitive than areother conditions.microscopical methods.5.4 Petrographic examination of aggregate considered for4.2 Identification of the constituents of a sample is usually ause in hydraulic-cement concrete is one aspect of the evalua-necessary step towards recognition of the properties that maytion of aggregate,but petrographic examination is also used forbe expected to influence the behavior of the material in itsmany other purposes.Petrographic examinations provide iden-intended use,but identification is not an end in itself.The valuetification of types and varieties of rocks present in potentialof any petrographic examination will depend to a large extentaggregates.However,as noted above,identification of everyon the representativeness of the samples examined,the com-rock and mineral present in an aggregate source is not required.pleteness and accuracy of the information provided to the5.5 The petrographic examination should establish whetherpetrographer concerning the source and proposed use of thematerial,and the petrographers ability to correlate these datathe aggregate contains chemically unstable minerals(such assoluble sulfates)or volumetrically unstable materials,such aswith the findings of the examination.smectites(formerly known as the montmorillonite-saponite4.3 This guide does not attempt to describe the techniquesgroup of minerals or swelling clays).Specifications may limitof petrographic work since it is assumed that the guide will bethe quartz content of aggregates for use in concrete that may beused by persons who are qualified by education and experiencesubject to high temperature(purposefully or accidentally)to employ such techniques for the recognition of the charac-because of the conversion to beta-quartz at 573 C 1063 F.teristic properties of rocks and minerals and to describe andwith accompanying volume increase.classify the constituents of an aggregate sample.In some cases,the petrographer will have had experience adequate to provide5.6 The petrographic examination should establish whetherdetailed interpretation of the results.In others,the interpreta-the aggregate contains iron sulfide minerals that may poten-tion will be made in part by engineers or others qualified totially oxidize within the concrete.Pyrite,marcasite,or pyrrho-relate the observations to the questions to be answered.tite may cause popouts and rust staining if present near thesurface of the concrete.Pyrrhotite within some rock types,in5.Significance and Usethe presence of moisture,has been found to oxidize and expand5.1 Petrographic examinations are made for the followingcausing significant cracking within concrete.Oxidation of ironsulfide minerals within concrete can lead to sulfuric acidpurposes:5.1.1 To determine the physical and chemical characteristicsattack,sulfate attack,or both.of the material that may be observed by petrographic methods5.7 Petrographic examination should identify the portion ofand that have a bearing on the performance of the material ineach coarse aggregate that is composed of weathered orits intended use.otherwise altered particles and the extent of that weathering or5.1.2 To describe and classify the constituents of thealteration,whether it is severe,moderate,or slight,and shouldsample,determine the proportion of each rock type in each condition.5.1.3 To determine the relative amounts of the constituentsIf the concrete in which the aggregate may be used will beof the sample that are essential for proper evaluation of theexposed to freezing and thawing in a critically saturatedsample when the constituents differ significantly in propertiescondition,finely porous and highly weathered or otherwisethat have a bearing on the performance of the material in itsaltered rocks should be identified because they will be espe-intended use,andcially susceptible to damage by freezing and thawing and willC295/C295M-19cause the aggregate portion of the concrete to fail in freezingreasonable assurance that the petrographic examination resultsand thawing.This will ultimately destroy the concrete becausewherever and whenever obtained may confidently be com-such aggregates cannot be protected by adequately air-pared.entrained mortar.Finely porous aggregates near the concrete6.Apparatus and Suppliessurface are also likely to form popouts,which are blemishes onpavements and walls.6.1 The apparatus and supplies listed as follows comprise aselection that will permit the use of the procedures described in5.8 Petrographic examinations may also be used to deter-this guide.All specific items listed have been used,in connec-mine the proportions of cubic,spherical,ellipsoidal,pyramidal,tion with the performance of petrographic examinations,by thetabular,flat,and elongated particles in an aggregate sample orprocedures described herein:it is not,however,intended tosamples.Flat,elongated,and thin chip-like particles in aggre-imply that other items cannot be substituted to serve similargate increase the mixing water requirement and hence decreasefunctions.Whenever possible the selection of particular appa-concrete strength.ratus and supplies should be left to the judgment of the5.9 Petrographic examination should identify and call atten-petrographer who is to perform the work so that the itemstion to potentially alkali-silica reactive and alkali-carbonateobtained will be those with the use of which the petrographerhas the greatest experience and familiarity.The minimumreactive constituents,determine such constituentsquantitatively,and recommend additional tests to confirm orequipment regarded as essential to the making of petrographicexaminations of aggregate samples are those items,or equiva-refute the presence in significant amounts of aggregate con-lent apparatus or supplies that will serve the same purpose,thatstituents capable of alkali reaction in concrete.See Specifica-are indicated by asterisks in the lists given as follows.tion C33/C33M.Alkali-silica reactive constituents found in6.1.1 Apparatus and Supplies for Preparation of Specimens:aggregates include:opal,chalcedony,cristobalite,tridymite,6.1.1.1 Rock-Cutting Saw*,preferably with 350-mm 14-highly strained quartz,microcrystalline quartz,cryptocrystal-in.diameter or larger diamond blade,and automatic feed.line quartz,volcanic glass,and synthetic siliceous glass.6.1.1.2 Horizontal Grinding Wheel,preferably 400-mmAggregate materials containing these constituents include:16-in.diameter.glassy to cryptocrystalline intermediate to acidic volcanic6.1.1.3 Polishing Wheel,preferably 200-to 300-mm 8 torocks,some argillites,phyllites,graywacke,gneiss,schist,12-in.diameter.gneissic granite,vein quartz,quartzite,sandstone,chert,and6.1.1.4 Abrasives*,Silicon carbide grit No.100 122 um.carbonate rocks containing alkali reactive forms of silica.22063uml,32031uml,60016uml,and80012um小：Criteria are available for identifying the minerals in the listalumina M-3055ml.fabove by their optical properties or by XRD(2),(3).Criteria are6.1.1.5 Geologists Pick or Hammer.available for identifying rocks by their mineral composition6.1.1.6 Microscope Slides*,clear,noncorrosive,25 byand texture(4).Examination in both reflected and transmitted45 mm 1 by 2 in.in size.light may be necessary to provide data for these identifications.6.1.1.7 Mounting Medium for Powder Mounts*CanadaX-ray microanalysis using energy-dispersive x-ray spectrom-balsam,neutral,in xylene;suitable low-viscosity epoxy resins;eters with scanning electron microscopy(SEM/EDX)oror Lakeside 70.wavelength-dispersive x-ray spectrometers in electron micro-6.1.1.8 Xylene*.probes(EMPA/WDX)may provide useful information on the6.1.1.9 Mounting Medium*,suitable for mounting rockchemical composition of minerals and rocks.Potentially del-slices for thin sections.eterious alkali-carbonate reactive rocks are usually calcareous6.1.1.10 Laboratory Oven*dolomites or dolomitic limestones with clayey insoluble resi-6.1.1.11 Plate-Glass Squares*,about 300 mm 12 in.on andues.Some dolomites essentially free of clay and some veryedge for thin-section grinding.fine-grained limestones free of clay and with minor insoluble6.1.1.12 Sample Splitter with pans.*6.1.1.13 Micro Cover Glasses*noncorrosive,square,12 toresidue,mostly quartz,are also capable of some alkali-18 mm,25 mm,0.5 to 0.75 in.,1.0 in.,and so forth.carbonate reactions,however,such reactions are not necessar-6.1.1.14 Plattner Mortar.ily deleterious.6.1.2 Apparatus and Supplies for Examination of Speci-5.10 Petrographic examination may be directed specificallymens:at the possible presence of contaminants in aggregates,such as6.1.2.1 Petrographic Microscope*,with mechanical stage;synthetic glass,cinders,clinker,or coal ash,magnesium oxide,oculars and objective lenses that will allow magnifications ofcalcium oxide,or both,gypsum,soil,hydrocarbons,chemicalsup to 600 x,and objective-centering devices;full-and quarter-that may affect the setting behavior of concrete or the proper-wave compensators;quartz wedge;micrometer eyepiece;Ber-ties of the aggregate,animal excrement,plants or rottentrand lens.vegetation,and any other contaminant that may prove unde-6.1.2.2 Microscope Lamps*sirable in concrete.6.1.2.3 Stereoscopic Microscope*,with objectives and ocu-lars to give final magnifications from about 6x to about 150 x.5.11 These objectives,for which this guide was prepared,will have been attained if those involved with the evaluation of4The values given in micrometres are the approximate average grain size ofaggregate materials for use in concrete construction havecommercial silicon carbide grit in the designated size classification.4C295/C295M-196.1.2.4 Magnet*,preferably Alnico,or an electromagnet.Drilling of such cores should be in a direction that is essentially6.1.2.5 Needleholder and Points*.perpendicular to the dominant structural feature of the rock.6.1.2.6 Dropping Bottle,60-mL 2 oz.capacity.Massive material may be sampled by NX(50-mm 2-in.6.1.2.7 Petri Culture Dishesdiameter)cores.Thinly bedded or complex material should be6.1.2.8 Forceps,smooth,straightpointed.represented by cores not less than 100 mm 4 in.in diameter.6.1.2.9 Lens Paper.*There should be an adequate number of cores to cover the6.1.2.10 Immersion Media*.n=1410 to n=1.785 inlimits of the deposit proposed for the project.The entiresteps of no more than 0.005.footage of the recovered core should be included in the sample6.1.2.11 Counter.and accurate data given as to elevations,depths,and core6.1.2.12 Photomicrographic Camera and accessories.losses.6.2 The items under Apparatus and Supplies include those7.1.2 Operating quarries and operating sand and graveldeposits,in which stock piles of the material produced areused to make thin sections.Semiautomatic thin section ma-available,should be represented by not less than 45 kg 100 Ibchines are available,and there are several thin-section makersor 300 pieces,whichever is larger,of each size of material towho advertise in Geotimes,the American Mineralogist,andbe examined.Samples from stock piles should be composed ofother mineralogical or geological journals.Laboratories mayrepresentative portions of larger samples collected with duefind it reasonable to buy a thin-section machine or use aconsideration given to segregation in the mercial thin-section maker.Remotely located laboratories7.1.3 Exposed faces of nonproducing quarries,where stockhave more need to be able to make their own thin sections.piles of processed material are not available,should be6.3 It is necessary that facilities be available to the petrog-represented by not less than 2 kg 4 Ibfrom each distinctiverapher to check the index of refraction of the immersion media.stratum or bed,with no piece having a mass less than 0.5 kg 1If accurate identification of materials is to be attempted,as forlb,or by a drilled core as described above.example the differentiation of quartz and chalcedony,or the7.1.4 Undeveloped sand and gravel deposits should bedifferentiation of basic from intermediate volcanic glass,thesampled by means of test pits dug to the anticipated depth ofindices of refraction of the media need to be known withfuture economic production.Samples should consist of not lessaccuracy.Media will not be stable for very long periods of timethan the quantities of material indicated in Table 1,selected soand are subject to considerable variation due to temperatureas to be representative of the deposits.change.In laboratories not provided with close temperaturecontrol,it is often necessary to recalibrate immersion mediaNATURAL GRAVEL AND SANDseveral times during the course of a single day when accurate8.Procedureidentifications are required.The equipment needed for check-ing immersion media consists of an Abbe refractometer.The8.1 Selection of Samples for Examination-Samples ofrefractometer should be equipped with compensating prisms togravel and natural sand for petrographic examination should beread indices for sodium light from white light,or it should bedry sieved in accordance with Method C136/C136M to provideused with a sodium arc lamp.samples of each sieve size.In the case of sands an additionalportion should then be tested in accordance with Test Method6.4 A laboratory that undertakes any considerable amount ofpetrographic work should be provided with facilities to makeC117,with the wash water being saved and removed by dryingin order to provide a sample of the material passing the 75-umphotomicrographic records of such features as cannot ad-(No.200)sieve(See Specification E11).The results of theequately be described in words.For illustrations of typicalapparatus,reference may be made to Ref(1)and manufacturerssieve analysis of each sample made in accordance with Methodof microscopes equipped with cameras and photomacrographicequipment may be consulted.Much useful guidance regardings Sieve size is identified by its standard designation in Specification E11.Thephotomicrography,especially using reflected light,is found inalterative designation given in parentheses is for information only and does notGuide E883.represent a different standard sieve size.7.SamplingTABLE 1 Minimum Sizes for Samples from Undeveloped Sandand Gravel Deposits7.1 Samples for petrographic examination should be takenby or under the direct supervision of a geologist familiar withQuantitySieve Sizethe requirements for random sampling of aggregates forkgbPiecesBconcrete and in general following the requirements of PracticeLarger than 150-mm(6-in.)75to150-mm(3to6-in.)43006D75/D75M.Information on the exact location from which the37.5to75-mm(1hto3-in.)41804001sample was taken,the geology of the site,and other pertinent19.0to37.5-mm(4to1-in902001data should be submitted with the sample.The amount of4.75 to 19.0-mm(No.4 to 34-in.)451001Finer than 4.75-mm(No.4)Ac50material actually studied in the petrographic examination willASieve size is identified by its standard designation in Specification E11.Thebe determined by the nature of the examination to be made andalternative designation given in parentheses is for information only and does notthe nature of the material to be examined,as discussed belowrepresent a ditferent standard sieve size.7.1.1 Undeveloped quarries should be sampled by means ofNot less than one piece from each apparent type of rockFine aggregate.cores drilled through the entire depth expected to be exploited.C295/C295M-19C136/C136M should be provided to the petrographer makingdiffraction,may be required or might most rapidly serve tothe examination and used in calculating results of the petro-identify fine-grained rock materials.graphic examination.Each sieve fraction should be examined9.3 Condition-The separated groups belonging to eachseparately,starting with the largest size available.Rocks arerock type should be examined to determine whether a furthermore easily recognized in larger pieces;the breakdown of aseparation by physical condition is necessary.If all of theheterogeneous type present in the larger sizes may haveparticles of a rock type are in a similar condition,that factprovided particles of several apparently different types in theshould be noted.More frequently,particles in several degreessmaller sizes.Some important and easily confused types mayof weathering will be found in a group.They should be sortedbe recognizable using the stereoscopic microscope if they areinto categories based on condition and on the expectation offirst recognized and separated in the larger sizes,but maycomparable behavior in concrete.The types of categoriesrequire examination using the petrographic microscope if theyintended are:(/fresh,dense;(2)moderately weathered;(3)are first encountered in the smaller sizes.very weathered;or(1)dense;(2)porous(or porous and8.2 The number of particles of each sieve fraction to befriable).It usually is not practicable to recognize more thanexamined will be fixed by the required precision of determi-three conditions per rock type,and one or two may benation of the less abundant constituents.Assuming that thesufficient.An important constituent present in larger quantitiesfield sampling and laboratory sampling procedures are accuratemay sometimes require separation into four groups by condi-and reliable,the number of particles examined,identified,andtion.The conspicuous example is chert when it is the majorcounted in each sieve fraction will depend on the requiredconstituent of a gravel sample.It may be present as dense,accuracy of the estimate of constituents present in smallunfractured chert;as vuggy chert;as porous chert;and as densequantities.The numbers given in this method are minimal.but highly fractured chert.The determination of which of theseThey are based on experience and on statistical considerationsfour conditions characterizes a particle may be expected to(5,6).It is believed that at least 150 particles of each sievehave an important influence on prediction of the behavior offraction should be identified and counted in order to obtainthe particle in concrete.reliable results.Precise determinations of small quantities of an9.4 Record:important constituent will require counts of larger numbers of9.4.1 Notes should be taken during the examination.Eachparticles.If the sample of a sieve fraction contains many morerock type should be described;the relevant features mayparticles than need to be identified,the sample shall be reducedinclude the following:in accordance with one of the procedures in Practice C702/9.4.1.1 Particle shape,C702M,so as to contain a proper number of particles for9.4.1.2 Particle surface texture,examination9.4.1.3 Grain size,9.4.1.4 Internal structure,including observations of pore9.Procedure for Examination of Natural Gravelspace,packing of grains,cementation of grains,9.4.1.5 Color,9.1 Coatings-The particles should be examined to estab-9.4.1.6 Mineral composition,lish whether exterior coatings are present.If coatings arepresent,it should be determined whether the coatings consist of9.4.1.7 Significant heterogeneities,9.4.1.8 General physical condition of the rock type in thematerials likely to be deleterious in concrete(opal,gypsum,sample,easily soluble salts,organic matter).It should also be deter-9.4.1.9 Coatings or incrustations,andmined qualitatively how firmly the coatings are bonded to the9.4.1.10 Presence of constituents known to cause deleteri-particles.ous chemical reaction in concrete.9.2 Rock Types-The sieve fraction should be sorted into9.4.2 Particle counts should be recorded so that tables canrock types by visual examination.If all or most of the groupsbe made for inclusion in the report.When the examination haspresent are types easily identifiable in hand specimen bybeen completed,the notes should contain enough informationexamination of a natural or broken surface,and by scratch andto permit the preparation of tables and descriptions.Tablesacid tests,no further identification may be needed.Fine-should be prepared showing the composition and condition ofgrained rocks that cannot be identified macroscopically or thatthe samples by sieve fractions,and the weighted averagemay consist of or contain constituents known to be deleteriouscomposition,based on the grading of the sample as receivedin concrete should be checked by examination with theand on the distribution of constituents by sieve fractionsstereoscopic microscope.If they cannot be identified by thatDescriptions of constituent groups should be prepared contain-means,they should be examined by means of the petrographicing the relevant features among those enumerated in themicroscope.The amount of work done in identifying fine-preceding list.grained rocks should be adapted to the information neededabout the particular sample.Careful examination of one size of10.Procedure for Examination of Natural Sanda sample,or study of information from previous examination10.1 The procedure for the examination of natural sand isof samples from the same source,will usually reveal thesimilar to that for the examination of gravel,with the modifi-amount of additional detailed microscopical work required tocations necessitated by the differences in particle size.obtain information adequate for the purpose.In some instances,10.1.1 Sizes Coarser than 600 um(No.30)-Each sievepetrographic methods other than microscopy,such as X-rayfraction present that is coarser than the 600-um(No.30)sieve5