1、Designation: C856 13C856 14Standard 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 nu
2、mber in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope Scope*1.1 This practice outlines procedures for the petrographic examination of samples of hardened concrete. The samples examinedmay be tak
3、en from concrete constructions, they may be concrete products or portions thereof, or they may be concrete or mortarspecimens that have been exposed in natural environments, or to simulated service conditions, or subjected to laboratory tests. Thephrase “concrete constructions” is intended to includ
4、e all sorts of objects, units, or structures that have been built of hydrauliccement concrete.NOTE 1A photographic chart of materials, phenomena, and reaction products discussed in Sections 8 13 and Tables 1-6 are available as AdjunctC856 (ADJCO856).1.2 The petrographic procedures outlined herein ar
5、e applicable to the examination of samples of all types of hardenedhydraulic-cement mixtures, including concrete, mortar, grout, plaster, stucco, terrazzo, and the like. In this practice, the materialfor examination is designated as “concrete,” even though the commentary may be applicable to the oth
6、er mixtures, unless thereference is specifically to media other than concrete.NOTE 2Appendix X1 outlines an uranyl acetate method for identifying locations where alkali-silica gel may be present. It is a requirement that thesubstances in those locations must be identified using any other more defini
7、tive techniques, such as petrographic microscopy.1.3 Annex A1 outlines an uranyl acetate method for identifying locations where alkali-silica gel may be present. It is arequirement that the substances in those locations must be identified using any other more definitive techniques, such aspetrograph
8、ic microscopy.1.3 The purposes of and procedures for petrographic examination 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 Samples 9S
9、pecimen Preparation 10Visual and Stereomicroscope Examination 11Polarizing Microscope Examination 12Paste Features 13Report 141.4 The values stated in inch-pound units are to be regarded as the standard. The SI units in parentheses are provided forinformation purposes only.1.5 This standard does not
10、 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 applicability of regulatorylimitations prior to use. A specific hazard statement is given in 6.
11、2.10.1.2. Referenced Documents2.1 ASTM Standards:2C125 Terminology Relating to Concrete and Concrete Aggregates1 This practice 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 app
12、roved Nov. 1, 2013June 1, 2014. Published December 2013June 2014. Originally approved in 1977. Last previous edition approved in 20112013 asC85611. DOI: 10.1520/C0856-13. 13. DOI: 10.1520/C0856-14.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at
13、 serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This 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 vers
14、ion. Becauseit may not be technically 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 sect
15、ion appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1C215 Test Method for Fundamental Transverse, Longitudinal, and Torsional Resonant Frequencies of Concrete SpecimensC227 Test Method for Potential A
16、lkali Reactivity of Cement-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 Ground Blast-Furnace Slag in Preventing Excessive Expansion of ConcreteDue to the Alk
17、ali-Silica ReactionC452 Test Method for Potential Expansion of Portland-Cement Mortars Exposed to SulfateC457 Test Method for Microscopical Determination of Parameters of the Air-Void System in Hardened ConcreteC496/C496M Test Method for Splitting Tensile Strength of Cylindrical Concrete SpecimensC5
18、97 Test Method for Pulse Velocity Through ConcreteC803/C803M Test Method for Penetration Resistance of Hardened ConcreteC805 Test Method for Rebound Number of Hardened ConcreteC823 Practice for Examination and Sampling of Hardened Concrete in ConstructionsC1012 Test Method for Length Change of Hydra
19、ulic-Cement Mortars Exposed to a Sulfate SolutionC1260 Test Method for Potential Alkali Reactivity of Aggregates (Mortar-Bar Method)E3 Guide for Preparation of Metallographic SpecimensE883 Guide for ReflectedLight Photomicrography3 The last approved version of this historical standard is referenced
20、on www.astm.org.TABLE 1 Visual Examination of Concrete (1)65Coarse Aggregate + Fine Aggregate + Matrix + Air + Embedded ItemsComposition:Maximum dimension,A in. ormm, in the range dType: Type: color, by comparison withNational ResearchCouncil Rock ColorChart (1963)more than 3 % of total, Type, size,
21、 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 5 Mixed 1 +
22、 /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 filledFabric:Sh
23、apeDistributionPackingGrading (even, uneven,distributionparticle shapegradingpreferred orientation6 as per-ceptible distribution shapedistributiongrading (as perceptible)parallelism of long axes of voids below horizontalor low-anglereinforcementexcess, or deficiency of irregular voids or sheetssize
24、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 sound? C
25、an 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 corroded?A
26、re cracks associatedwith embeddeditems?A A substantial portion of the coarse aggregate has maximum dimensions in the range shown as measured on sawed or broken surfaces.B Sections sawed or drilled close to and parallel to formed surfaces appear to show local turbulence as a result of spading or rodd
27、ing 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 upper pie
28、ce as cast and sockets abundant on the top of the lower piece as cast.C856 1422.2 ASTM Adjuncts:Adjunct C856 (ADJCO856) A chart of 27 photos43. Terminology3.1 Definitions:For definitions of terms used in this practice, refer to Terminology C125.4. Qualifications of Petrographers and Use of Technicia
29、ns4.1 All petrographic examinations of hardened concrete described in this practice shall be performed by or under the technicaldirection of a full time supervising petrographer with at least 5 years experience in petrographic examinations of concrete andconcrete-making materials. The supervising co
30、ncrete petrographer shall have college level courses that include petrography,mineralogy, and optical mineralogy, or 5 years of documented equivalent experience, and experience in their application toevaluations of concrete-making materials and concrete products in which they are used and in cementi
31、tious-based materials. Aresume of the professional background and qualifications of all concrete petrographers shall be available.4.2 A concrete petrographer shall be knowledgeable about the following: concrete-making materials; processes of batching,mixing, handling, placing, and finishing of hydra
32、ulic-cement concrete; the composition and microstructure of cementitious paste;the interaction of constituents of concrete; and the effects of exposure of such concrete to a wide variety of conditions of service.4.3 Sample preparation shall be performed by concrete petrographers or trained technicia
33、ns pursuant to instructions from andunder the guidance of a qualified concrete petrographer. Aspects of the petrographic examination, such as the measurement ofsample dimensions, photography of as-received samples, staining of sample surfaces, that do not require the education and skillsoutlined in
34、4.1, shall be performed by concrete petrographers or by trained technicians pursuant to instructions and under theguidance of a qualified concrete petrographer. The analysis and interpretation of the features that are relevant to the investigationand evaluation of the performance of the materials re
35、presented by the sample shall be made solely by concrete petrographers withqualifications consistent with those outlined in 4.1.4 Available from ASTM International Headquarters. Order Adjunct No. ADJC0856. Original adjunct produced in 1995.TABLE 2 Outline for Examination of Concrete with a Stereomic
36、roscope (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 of its natural moisture content has a luster that in mineralogical terms is subtranslucent glimmering vitreous.A Thin edges of splinte
37、rs 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 lessintense. Concrete in less good physical condition is more opaque on a freshly broken surface, and the luster is dull, subvitreous going t
38、oward chalky. Aproperly cured laboratory specimen from a concrete mixture of normal proportions cured 28 days that has shown normal compressive or 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
39、 of concretein good physical condition.Under the same conditions of examination, when there is reasonable assurance that the concrete does not contain white portland cement or slagcement, the color of the matrix of concrete in good physical condition is definitely gray or definitely tan, except adjo
40、ining old cracks or original surfaces.Coarse Aggregate Fine Aggregate Matrix VoidsLithologic types and mineralogy as percep- Lithologic types and miner- Color Gradingtible alogy as perceptible Fracture around or through aggregate Proportion of spherical to nonsphericalSurface texture Shape Contact o
41、f matrix with aggregate: Nonspherical, ellipsoidal, irregular, disk-Within the piece: Surface texture close, no opening visible on sawed shapedGrain shape Grading or broken surface; aggregate not Color change from interior surface toGrain size extreme range observed, mm Distribution dislodged with f
42、ingers or probe; matrixMedian within range _ to _ mm boundary openings frequent, Interior surface luster like rest of ma-Textureless (too fine to resolve) common, rare trix, dull, shiningUniform or variable within the piece Width Linings in voids absent, rare, common,From piece to piece: Empty in mo
43、st, complete, partial, colorless,Intergranular bond Filled colored, silky tufts, hexagonal tab-Porosity and absorptionB Cracks present, absent, result of spec- lets, gel, otherIf concrete breaks through aggregate, imen preparation, preceding spec- Underside voids or sheets of voids un-through how mu
44、ch 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? BleedingSegregationA Dana, E. S., Textbook of Mineralogy, revised by W.
45、 E. Ford, John Wiley dehydration isessentially complete at 540C; calcium hydroxide goesto CaO at 450500C. Paste expands with thermalcoefficient effect and then shrinks, cracks, decrepitates,and becomes soft (2).Beneath the softened concrete, which can be testedin accordance with Test Method C805, th
46、econcrete is probably normal if it has not undergonecolor change. Establish by coring for compressivetests, by wear tests (CRD-C 52) (2), and byscratching with a knife.Cracking Perpendicular to the face and internal, where heating orcooling caused excess tensile stresses. In some newconcrete, resemb
47、les large-scale shrinkage cracking; maypenetrate up to 100 mm but may heal autogenously (2).Examination of the surface, ultrasonic tests, coring,petrographic examination (2).Color changeWhen concrete has notspalled, observe depth of pink color toestimate the fire exposure.Concrete made with sediment
48、ary 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 sil
49、iceous aggregate (3). At 573Clow quartz inverts to high with 0.85 % increase involume, producing popouts. Spalling over steel toexpose one fourth of the bar at 790C; white powdereddecomposed hydration products at 900C. Surfacecrazing about 290C; deeper cracking about 540C.Color change is the factor most useful to theinvestigator; permits recognizing how deeply atemperature of about 300C occurred (3).Aggregate behaviorAggregate behavioraffects strength, modulus, spalling,cracking, surface hardness, and residualthermal strains (2).Aggregates differ in thermal
