1、Designation: C856 13Standard 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. Scope1.1 This practice outlines procedures for the petrographicexamination of samples of hardened concrete. The samplesexamined may be taken from concret
3、e 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 obj
4、ects, 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 the
6、 reference is specifically to media otherthan concrete.1.3 Annex A1 outlines an uranyl acetate method for identi-fying locations where alkali-silica gel may be present. It is arequirement that the substances in those locations must beidentified using any other more definitive techniques, such aspetr
7、ographic microscopy.1.4 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 Apparatus 7Samples 8Examination of Sam
8、ples 9Specimen Preparation 10Visual and Stereomicroscope Examination 11Polarizing Microscope Examination 12Paste Features 13Report 141.5 The values stated in inch-pound units are to be regardedas the standard. The SI units in parentheses are provided forinformation purposes only.1.6 This standard do
9、es 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. A specific hazardstatement is give
10、n 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 Alkali Reactivity ofCement-Aggregate
11、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 Ground1This practice is under the jurisdiction of ASTM Committee C09 on Concreteand ConcreteAggregatesand is the direct re
12、sponsibility of Subcommittee C09.65 onPetrography.Current edition approved Nov. 1, 2013. Published December 2013. Originallyapproved in 1977. Last previous edition approved in 2011 as C85611. DOI:10.1520/C0856-13.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Cu
13、stomer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1Blast-Furnace Slag in Preventing E
14、xcessive Expansion ofConcrete Due to the Alkali-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
15、 Strength ofCylindrical Concrete SpecimensC597 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 ConstructionsC
16、1012 Test Method for Length Change of Hydraulic-Cement Mortars Exposed to a Sulfate SolutionC1260 Test Method for Potential Alkali Reactivity of Ag-gregates (Mortar-Bar Method)E3 Guide for Preparation of Metallographic SpecimensE883 Guide for ReflectedLight Photomicrography2.2 ASTM Adjuncts:Adjunct
17、C856 (ADJCO856) A chart of 27 photos43. Terminology3.1 Definitions:For definitions of terms used in this practice, refer toTerminology C125.4. Qualifications of Petrographers and Use of Technicians4.1 All petrographic examinations of hardened concretedescribed in this practice shall be performed by
18、or under thetechnical direction of a full time supervising petrographer withat least 5 years experience in petrographic examinations of3The last approved version of this historical standard is referenced onwww.astm.org.4Available from ASTM International Headquarters. Order Adjunct No.ADJC0856. Origi
19、nal adjunct produced in 1995.TABLE 1 Visual Examination of Concrete (1)6Coarse Aggregate + Fine Aggregate + Matrix + 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,
20、Type, size, location;kinds of metal; otheritems1 Gravel 1 Natural sand predominantly in spherical2 Crushed stone 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
21、5 Mixed 1 + /or 2 + /or 4 3 gradational changes voids?If Type 1, 2, or 4, homogeneousor heterogeneousIf Type 1, 2, or 4,homogeneous orheterogeneouscolor differences betweenvoids and mortar?Lithologic typesCoarse aggregate more than 20,30, 40, or 50 % of totalvoids empty, filled, lined, orpartly fill
22、edFabric:ShapeDistributionPackingGrading (even, uneven,distributionparticle shapegradingpreferred orientation6as per-ceptibledistribution shapedistributiongrading (as perceptible)parallelism of long axes ofvoids below horizontalor low-anglereinforcementexcess, or deficiency of irregular voids or she
23、etssize or sizes) of voids: with each other;Parallelism of flat sides orlong axes of exposedwith flat sides or longaxes 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
24、sound? Can you break it with your fingers? Cracks? How distributed?Through or around coarse aggregate? With cores or sawed 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 co
25、rroded?Are cracks associatedwith embeddeditems?AA substantial portion of the coarse aggregate has maximum dimensions in 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 o
26、r rodding close to the form. Sections sawedin the plane of bedding (normal to the direction of placement) are likely to 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 upp
27、er piece as cast and sockets abundant on the top of the lower piece as cast.C856 132concrete 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 experien
28、ce, and experience in theirapplication to evaluations 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 s
29、hall be knowledgeable aboutthe following: concrete-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
30、 concrete to a wide varietyof conditions of service.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
31、sample dimensions, photography of as-received samples, staining of sample surfaces, that do notrequire the education and skills outlined in 4.1, shall beperformed by concrete petrographers or by trained technicianspursuant to instructions and under the guidance of a qualifiedconcrete petrographer. T
32、he 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 concrete petrographers with qualifica-tions consistent with those outlined in 4.1.4.4 A concrete petrographer shall
33、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 interpretation of the findingsinsofar as they relate to the concerns of the person or agencyfor whom the examination was pe
34、rformed. Supplementaryinformation provided to the petrographer on the concrete andconcrete materials, conditions of service, or other features ofthe concrete construction may be helpful in interpreting thedata obtained during the petrographic examinations.4.5 This practice may form the basis for est
35、ablishing ar-rangements between a purchaser of the consulting service andthe consulting petrographer. In such cases, the purchaser of theconsulting service and the consulting petrographer shouldtogether determine the kind, extent, and objectives of theexaminations and analyses to be made, and may re
36、cord 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 conditions.5. Purposes of Examination5.1 Examples of purposes for which petrographic examina-tion of concrete is used
37、are given in 5.2 5.5. The probableusefulness of petrographic examination in specific instancesTABLE 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 tha
38、t stillretains most 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 broke
39、n glass but lessintense. 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
40、flexural strengthand 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 cont
41、ain white portland cement 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 m
42、iner- Color Gradingtible 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 shapedGrai
43、n shape Grading or broken 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 r
44、esolve) common, rare 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, resu
45、lt of spec- lets, gel, 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 MaterialsCaggregat
46、e? 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 thermalcoefficient effec
47、t and then shrinks, cracks, decrepitates,and becomes soft (2).Beneath the softened concrete, which can be testedin accordance with Test Method C805,theconcrete is probably normal if it has not undergonecolor change. Establish by coring for compressivetests, by wear tests (CRD-C 52) (2), and byscratc
48、hing with a knife.Cracking Perpendicular to the face and internal, where heating orcooling caused excess tensile stresses. In some newconcrete, resembles large-scale shrinkage cracking; maypenetrate up to 100 mm but may heal autogenously (2).Examination of the surface, ultrasonic tests, coring,petro
49、graphic examination (2).Color changeWhen concrete has notspalled, observe depth of pink color toestimate the fire exposure.Concrete made with sedimentary or metamorphicaggregates shows permanent color change on heating.Color normal to 230C; goes from pink to red from 290 to590C; from 590 to 900C color changes to gray andthen to buff (2). For temperatures up to about 500Ctemperature distribution is little affected by usingcarbonate rather than siliceous aggregate (3). At 573Clow quartz inverts to high with 0.85 % increase involume, producing popouts. Spalling over ste
