1、Designation: C856 17Standard Practice forPetrographic Examination of Hardened Concrete1This standard is issued under the fixed designation C856; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in
2、 parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This practice outlines procedures for the petrographicexamination of samples of hardened concrete. The samplesexamined may be taken from concre
3、te constructions, they maybe concrete products or portions thereof, or they may beconcrete or mortar specimens that have been exposed in naturalenvironments, or to simulated service conditions, or subjectedto laboratory tests. The phrase “concrete constructions” isintended to include all sorts of ob
4、jects, units, or structures thathave been built of hydraulic cement concrete.NOTE 1A photographic chart of materials, phenomena, and reactionproducts discussed in Sections 813and Tables 1-6 are available asAdjunct C856 (ADJCO856).1.2 The petrographic procedures outlined herein are appli-cable to the
5、 examination of samples of all types of hardenedhydraulic-cement mixtures, including concrete, mortar, grout,plaster, stucco, terrazzo, and the like. In this practice, thematerial for examination is designated as “concrete,” eventhough the commentary may be applicable to the othermixtures, unless th
6、e reference is specifically to media otherthan concrete.1.3 The purposes of and procedures for petrographic exami-nation of hardened concrete are given in the following sections:SectionQualifications of Petrographers and Use of Technicians 4Purposes of Examination 5Apparatus 6Selection and Use of Ap
7、paratus 7Samples 8Examination of Samples 9Specimen Preparation 10Visual and Stereomicroscope Examination 11Polarizing Microscope Examination 12Paste Features 13Report 141.4 The values stated in inch-pound units are to be regardedas the standard. The SI units in parentheses are provided forinformatio
8、n purposes only.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use
9、. A specific hazardstatement is given in 6.2.10.1.2. Referenced Documents2.1 ASTM Standards:2C125 Terminology Relating to Concrete and Concrete Ag-gregatesC215 Test Method for Fundamental Transverse,Longitudinal, and Torsional Resonant Frequencies ofConcrete SpecimensC227 Test Method for Potential A
10、lkali Reactivity ofCement-Aggregate Combinations (Mortar-Bar Method)C342 Test Method for Potential Volume Change of Cement-Aggregate Combinations (Withdrawn 2001)3C441 Test Method for Effectiveness of Pozzolans or GroundBlast-Furnace Slag in Preventing Excessive Expansion ofConcrete Due to the Alkal
11、i-Silica ReactionC452 Test Method for Potential Expansion of Portland-Cement Mortars Exposed to SulfateC457 Test Method for Microscopical Determination of Pa-rameters of the Air-Void System in Hardened ConcreteC496/C496M Test Method for Splitting Tensile Strength ofCylindrical Concrete SpecimensC597
12、 Test Method for Pulse Velocity Through ConcreteC803/C803M Test Method for Penetration Resistance ofHardened ConcreteC805 Test Method for Rebound Number of Hardened Con-creteC823 Practice for Examination and Sampling of HardenedConcrete in ConstructionsC1012 Test Method for Length Change of Hydrauli
13、c-Cement Mortars Exposed to a Sulfate SolutionC1260 Test Method for Potential Alkali Reactivity of Ag-gregates (Mortar-Bar Method)1This practice is under the jurisdiction of ASTM Committee C09 on Concreteand ConcreteAggregates and is the direct responsibility of Subcommittee C09.65 onPetrography.Cur
14、rent edition approved Jan. 1, 2017. Published March 2017. Originallyapproved in 1977. Last previous edition approved in 2014 as C856 14. DOI:10.1520/C0856-17.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of A
15、STMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, P
16、O Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued
17、by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1E3 Guide for Preparation of Metallographic SpecimensE883 Guide for ReflectedLight Photomicrography2.2 ASTM Adjuncts:Adjunct C856 (ADJCO856) A chart of 27 photos43. Terminology3.1 Definitions: For definitions of terms used i
18、n thispractice, refer to Terminology C125.4. Qualifications of Petrographers and Use of Technicians4.1 All petrographic examinations of hardened concretedescribed in this practice shall be performed by or under thetechnical direction of a full time supervising petrographer withat least 5 years exper
19、ience in petrographic examinations ofconcrete and concrete-making materials. The supervising con-crete petrographer shall have college level courses that includepetrography, mineralogy, and optical mineralogy, or 5 years ofdocumented equivalent experience, and experience in theirapplication to evalu
20、ations of concrete-making materials andconcrete products in which they are used and in cementitious-based materials. A resume of the professional background andqualifications of all concrete petrographers shall be available.4.2 A concrete petrographer shall be knowledgeable aboutthe following: concr
21、ete-making materials; processes ofbatching, mixing, handling, placing, and finishing of hydraulic-cement concrete; the composition and microstructure of ce-mentitious paste; the interaction of constituents of concrete;and the effects of exposure of such concrete to a wide varietyof conditions of ser
22、vice.4.3 Sample preparation shall be performed by concretepetrographers or trained technicians pursuant to instructionsfrom and under the guidance of a qualified concrete petrogra-pher. Aspects of the petrographic examination, such as themeasurement of sample dimensions, photography of as-received s
23、amples, staining of sample surfaces, that do notrequire the education and skills outlined in 4.1, shall be4Available from ASTM International Headquarters. Order Adjunct No.ADJC0856. Original adjunct produced in 1995.TABLE 1 Visual Examination of Concrete (1)5Coarse Aggregate + Fine Aggregate + Matri
24、x + Air + Embedded ItemsComposition:Maximum dimension,Ain. ormm, in the range dType: Type: color, by comparison withNational ResearchCouncil Rock ColorChart (1963)more than 3 % of total, Type, size, location;kinds of metal; otheritems1 Gravel 1 Natural sand predominantly in spherical2 Crushed stone
25、2 Manufactured sand color distribution: voids?3 Mixed 1 and 2 3 Mixed 1 mottled less than 3 % of total,4 Other (name) 4 Other (name) 2 even abundant nonspherical5 Mixed 1 + or 2 + or 4 5 Mixed 1 + or 2 + or 4 3 gradational changes voids?If Type 1, 2, or 4, homogeneousor heterogeneousIf Type 1, 2, or
26、 4,homogeneous orheterogeneouscolor differences betweenvoids and mortar?Lithologic typesCoarse aggregate more than 20,30, 40, or 50 % of totalvoids empty, filled, lined, orpartly filledFabric:ShapeDistributionPackingGrading (even, uneven,distributionparticle shapegradingpreferred orientation6as per-
27、ceptibledistribution shapedistributiongrading (as perceptible)parallelism of long axes ofvoids below horizontalor low-anglereinforcementexcess, or deficiency of irregular voids or sheetssize or sizes) of voids: with each other;Parallelism of flat sides orlong axes of exposedwith flat sides or longax
28、es of coarse aggregatesections, normal todirection of placement+ or parallel to formed andfinished surfacesBCondition:Does it ring when hit lightly with a hammer or give a dull flat sound? Can you break it with your fingers? Cracks? How distributed?Through or around coarse aggregate? With cores or s
29、awed specimens, did the aggregate tear in drilling or sawing? Crack fillings?Surface deposits? If air dry, are there unusually wet or dry looking areas? Rims on aggregate?clean or corroded?Are cracks associatedwith embeddeditems?AA substantial portion of the coarse aggregate has maximum dimensions i
30、n the range shown as measured on sawed or broken surfaces.BSections sawed or drilled close to and parallel to formed surfaces appear to show local turbulence as a result of spading or rodding close to the form. Sections sawedin the plane of bedding (normal to the direction of placement) are likely t
31、o have inconspicuous orientation. Sections broken normal to placement in conventionally placedconcrete with normal bond tend to have aggregate knobs abundant on the bottom of the upper piece as cast and sockets abundant on the top of the lower piece as cast.C856 172performed by concrete petrographer
32、s or by trained technicianspursuant to instructions and under the guidance of a qualifiedconcrete petrographer. The analysis and interpretation of thefeatures that are relevant to the investigation and evaluation ofthe performance of the materials represented by the sampleshall be made solely by con
33、crete petrographers with qualifica-tions consistent with those outlined in 4.1.4.4 A concrete petrographer shall be prepared to provide anoral statement, written report, or both that includes a descrip-tion of the observations and examinations made during thepetrographic examinations, and interpreta
34、tion of the findingsinsofar as they relate to the concerns of the person or agencyfor whom the examination was performed. Supplementaryinformation provided to the petrographer on the concrete andconcrete materials, conditions of service, or other features ofthe concrete construction may be helpful i
35、n interpreting thedata obtained during the petrographic examinations.4.5 This practice may form the basis for establishing ar-rangements between a purchaser of the consulting service andthe consulting petrographer. In such cases, the purchaser of theconsulting service and the consulting petrographer
36、 shouldtogether determine the kind, extent, and objectives of theexaminations and analyses to be made, and may record theiragreement in writing. The agreement may stipulate specificdeterminations to be made, observations to be reported, fundsto be obligated, or a combination of these and other condi
37、tions.5. Purposes of Examination5.1 Examples of purposes for which petrographic examina-tion of concrete is used are given in 5.2 5.5. The probableusefulness of petrographic examination in specific instancesmay be determined by discussion with an experienced petrog-rapher of the objectives of the in
38、vestigation proposed orunderway.5.2 Concrete from Constructions:5.2.1 Determination in detail of the condition of concrete ina construction.5.2.2 Determination of the causes of inferior quality,distress, or deterioration of concrete in a construction.5.2.3 Determination of the probable future perfor
39、mance ofthe concrete.5.2.4 Determination whether the concrete in a constructionwas or was not as specified. In this case, other tests may berequired in conjunction with petrographic examination.5.2.5 Description of the cementitious matrix, includingqualitative determination of the kind of hydraulic
40、binder used,degree of hydration, degree of carbonation if present, evidenceof unsoundness of the cement, presence of supplementarycementitious materials, the nature of the hydration products,adequacy of curing, and unusually high watercement ratio ofthe paste.5.2.6 Determination whether alkalisilica
41、 or alkalicarbon-ate reactions, or cementaggregate reactions, or reactionsTABLE 2 Outline for Examination of Concrete with a Stereomicroscope (1)NOTE 1ConditionWhen it is examined at 6 to 10 under good light, the freshly broken surface of a concrete in good physical condition that stillretains most
42、of its natural moisture content has a luster that in mineralogical terms is subtranslucent glimmering vitreous.AThin edges of splinters of thepaste transmit light; reflections appear to come from many minute points on the surface, and the quality of luster is like that from broken glass but lessinte
43、nse. Concrete in less good physical condition is more opaque on a freshly broken surface, and the luster is dull, subvitreous going toward chalky. Aproperly cured laboratory specimen from a concrete mixture of normal proportions cured 28 days that has shown normal compressive or flexural strengthand
44、 that is broken with a hammer and examined on a new break within a week of the time that it finished curing should provide an example of concretein good physical condition.Under the same conditions of examination, when there is reasonable assurance that the concrete does not contain white portland c
45、ement or slagcement, the color of the matrix of concrete in good physical condition is definitely gray or definitely tan, except adjoining old cracks or original surfaces.Coarse Aggregate Fine Aggregate Matrix VoidsLithologic types and mineralogy as percep- Lithologic types and miner- Color Gradingt
46、ible alogy as perceptible Fracture around or through aggregate Proportion of spherical to nonsphericalSurface texture Shape Contact of matrix with aggregate: Nonspherical, ellipsoidal, irregular, disk-Within the piece: Surface texture close, no opening visible on sawed shapedGrain shape Grading or b
47、roken surface; aggregate not Color change from interior surface toGrain size extreme range observed, mm Distribution dislodged with fingers or probe; matrixMedian within range _ to _ mm boundary openings frequent, Interior surface luster like rest of ma-Textureless (too fine to resolve) common, rare
48、 trix, dull, shiningUniform or variable within the piece Width Linings in voids absent, rare, common,From piece to piece: Empty in most, complete, partial, colorless,Intergranular bond Filled colored, silky tufts, hexagonal tab-Porosity and absorptionBCracks present, absent, result of spec- lets, ge
49、l, otherIf concrete breaks through aggregate, imen preparation, preceding spec- Underside voids or sheets of voids un-through how much of what kind? imen preparation common, small, common, abundantIf boundary voids, along what kind of Supplementary Cementitious MaterialsCaggregate? All? All of one kind? More Contaminationthan 50 % of one kind? Several kinds? BleedingSegregationADana, E. S., Textbook of Mineralogy, revised by W. E. Ford, John Wiley dehydration isessentially complete at 540C; calcium hydroxide goesto CaO at 450500C. Paste expands with thermalcoeffi
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