ASTM C856/C856M-20

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: C856/C856M − 20
Standard Practice for
Petrographic Examination of Hardened Concrete
This standard is issued under the fixed designation C856/C856M; the number immediately following the designation indicates the year
of original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.
A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
fication E11. The alternative designation given in parentheses is for
1. Scope*
information only and does not represent a different standard sieve size.
1.1 This practice outlines procedures for the petrographic
1.5 This standard does not purport to address all of the
examination of samples of hardened concrete. The samples
safety concerns, if any, associated with its use. It is the
examined may be taken from concrete constructions, they may
responsibility of the user of this standard to establish appro-
be concrete products or portions thereof, or they may be
priate safety, health, and environmental practices and deter-
concreteormortarspecimensthathavebeenexposedinnatural
mine the applicability of regulatory limitations prior to use. A
environments, or to simulated service conditions, or subjected
specific hazard statement is given in 6.2.10.1.
to laboratory tests. The phrase “concrete constructions” is
1.6 This international standard was developed in accor-
intended to include all sorts of objects, units, or structures that
dance with internationally recognized principles on standard-
have been built of hydraulic cement concrete.
ization established in the Decision on Principles for the
1.2 The petrographic procedures outlined herein are appli-
Development of International Standards, Guides and Recom-
cable to the examination of samples of all types of hardened
mendations issued by the World Trade Organization Technical
mixtures, including concrete, mortar, grout, plaster, stucco,
Barriers to Trade (TBT) Committee.
terrazzo, and the like. In this practice, the material for
2. Referenced Documents
examination is designated as “concrete,” even though the
commentary may be applicable to the other mixtures, unless
2.1 ASTM Standards:
the reference is specifically to media other than concrete.
C125Terminology Relating to Concrete and Concrete Ag-
gregates
1.3 Thepurposesofandproceduresforpetrographicexami-
C215 Test Method for Fundamental Transverse,
nationofhardenedconcretearegiveninthefollowingsections:
Longitudinal, and Torsional Resonant Frequencies of
Section
Concrete Specimens
Qualifications of Petrographers and Use of Technicians 4
C452Test Method for Potential Expansion of Portland-
Purposes of Examination 5
Cement Mortars Exposed to Sulfate
Apparatus 6
C457Test Method for Microscopical Determination of Pa-
Selection and Use of Apparatus 7
Samples 8
rameters of the Air-Void System in Hardened Concrete
Examination of Samples 9
C597Test Method for Pulse Velocity Through Concrete
Specimen Preparation 10
C803/C803MTest Method for Penetration Resistance of
Visual and Stereomicroscope Examination 11
Polarizing Microscope Examination 12
Hardened Concrete
Paste Features 13
C805Test Method for Rebound Number of Hardened Con-
Report 14
crete
1.4 The values stated in either SI units or inch-pound units
C823Practice for Examination and Sampling of Hardened
are to be regarded separately as standard. The values stated in
Concrete in Constructions
eachsystemarenotnecessarilyexactequivalents;therefore,to
C1012 Test Method for Length Change of Hydraulic-
ensure conformance with the standard, each system shall be
Cement Mortars Exposed to a Sulfate Solution
used independently of the other, and values from the two
C1723Guide for Examination of Hardened Concrete Using
systems shall not be combined.
Scanning Electron Microscopy
NOTE 1—Sieve size is identified by its standard designation in Speci-
E3Guide for Preparation of Metallographic Specimens
E11Specification forWovenWireTest Sieve Cloth andTest
Sieves
This practice is under the jurisdiction of ASTM Committee C09 on Concrete
andConcreteAggregatesandisthedirectresponsibilityofSubcommitteeC09.65on
Petrography. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Jan. 15, 2020. Published February 2020. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1977. Last previous edition approved in 2018 as C856–18a. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/C0856_C0856M-20. the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C856/C856M − 20
E883Guide for Reflected–Light Photomicrography determinations to be made, observations to be reported, funds
tobeobligated,oracombinationoftheseandotherconditions.
3. Terminology
5. Purposes of Examination
3.1 Definitions: For definitions of terms used in this
practice, refer to Terminology C125.
5.1 Examples of purposes for which petrographic examina-
tion of concrete is used are given in 5.2 – 5.5. The probable
4. Qualifications of Petrographers and Use of Technicians
usefulness of petrographic examination in specific instances
may be determined by discussion with an experienced petrog-
4.1 All petrographic examinations of hardened concrete
described in this practice shall be performed by or under the rapher of the objectives of the investigation proposed or
underway.
technical direction of a full time supervising petrographer with
at least five years experience in petrographic examinations of
5.2 Concrete from Constructions:
concrete and concrete-making materials. The supervising con-
5.2.1 Determination in detail of the condition of concrete in
crete petrographer shall have college level courses that include
a construction.
petrography, mineralogy, and optical mineralogy, or five years
5.2.2 Determination of the causes of inferior quality,
of documented equivalent experience, and experience in their
distress, or deterioration of concrete in a construction.
application to evaluations of concrete-making materials and
5.2.3 Determination of the probable future performance of
concrete products in which they are used and in cementitious-
the concrete.
based materials.Aresume of the professional background and
5.2.4 Determination whether the concrete in a construction
qualifications of all concrete petrographers shall be available.
was or was not as specified. In this case, other tests may be
4.2 A concrete petrographer shall be knowledgeable about required in conjunction with petrographic examination.
the following: concrete-making materials; processes of
5.2.5 Description of the cementitious matrix, including
batching, mixing, handling, placing, and finishing of concrete;
qualitative determination of the kind of binder used, degree of
the composition and microstructure of cementitious paste; the
hydration, degree of carbonation if present, evidence of un-
interaction of constituents of concrete; and the effects of
soundness of the cement, presence of supplementary cementi-
exposure of such concrete to a wide variety of conditions of
tious materials, the nature of the hydration products, adequacy
service.
of curing, and unusually high water–cement ratio of the paste.
5.2.6 Determination whether alkali–silica or alkali–carbon-
4.3 Sample preparation shall be performed by concrete
ate reactions, or cement–aggregate reactions, or reactions
petrographers or trained technicians pursuant to instructions
between contaminants and the matrix have taken place, and
from and under the guidance of a qualified concrete petrogra-
their effects upon the concrete.
pher. Aspects of the petrographic examination, such as the
5.2.7 Determination whether the concrete has been sub-
measurement of sample dimensions, photography of as-
jected to and affected by sulfate attack, or other chemical
received samples, staining of sample surfaces, that do not
attack, or early freezing, or to other harmful effects of freezing
require the education and skills outlined in 4.1, shall be
and thawing.
performed by concrete petrographers or by trained technicians
5.2.8 Part of a survey of the safety of a structure for a
pursuant to instructions and under the guidance of a qualified
present or proposed use.
concrete petrographer. The analysis and interpretation of the
5.2.9 Determination whether concrete subjected to fire is
features that are relevant to the investigation and evaluation of
essentially undamaged or moderately or seriously damaged.
the performance of the materials represented by the sample
5.2.10 Investigationoftheperformanceofthecoarseorfine
shall be made solely by concrete petrographers with qualifica-
aggregate in the structure, or determination of the composition
tions consistent with those outlined in 4.1.
of the aggregate for comparison with aggregate from approved
4.4 Aconcrete petrographer shall be prepared to provide an
or specified sources.
oral statement, written report, or both that includes a descrip-
5.2.11 Determination of the factors that caused a given
tion of the observations and examinations made during the
concrete to serve satisfactorily in the environment in which it
petrographic examinations, and interpretation of the findings
was exposed.
insofar as they relate to the concerns of the person or agency
5.2.12 Determination of the presence and nature of surface
for whom the examination was performed. Supplementary
treatments, such as dry shake applications on concrete floors.
information provided to the petrographer on the concrete and
5.3 Test Specimens from Actual or Simulated Service—
concrete materials, conditions of service, or other features of
the concrete construction may be helpful in interpreting the Concrete or mortar specimens that have been subjected to
actual or simulated service conditions may be examined for
data obtained during the petrographic examinations.
mostofthepurposeslistedunderConcretefromConstructions.
4.5 This practice may form the basis for establishing ar-
5.4 Concrete Products:
rangements between a purchaser of the consulting service and
theconsultingpetrographer.Insuchcases,thepurchaserofthe 5.4.1 Petrographic examination can be used in investigation
consulting service and the consulting petrographer should of concrete products of any kind, including masonry units,
together determine the kind, extent, and objectives of the precaststructuralunits,piling,pipe,andbuildingmodules.The
examinations and analyses to be made, and may record their productsorsamplesofthosesubmittedforexaminationmaybe
agreement in writing. The agreement may stipulate specific either from current production, from elements in service in
C856/C856M − 20
constructions, or from elements that have been subjected to generally used. Equipment required for field sampling is not
tests or to actual or simulated service conditions. listed. Any other useful equipment may be added.
5.4.2 Determination of features like those listed under
6.2 For Specimen Preparation:
concrete from constructions.
6.2.1 Diamond Saw—Slabbing saw with an automatic feed
5.4.3 Determination of effects of manufacturing processes
and blade large enough to make at least a 175-mm [7-in.] cut
and variables such as procedures for mixing, molding,
in one pass.
demolding, consolidation, curing, and handling.
6.2.2 Cutting Lubricant, for diamond saw.
5.4.4 Determination of effects of use of different concrete-
6.2.3 Horizontal Lap Wheel or Wheels, steel, cast iron, or
making materials, forming and molding procedures, types and
othermetallap,preferablyatleast400mm[16in.]indiameter,
amounts of reinforcement, embedded hardware, and so forth.
large enough to grind at least a 100 by 150-mm [4 by 6-in.]
5.5 Laboratory Specimens—The purposes of petrographic
area.
examination of laboratory specimens of concrete, mortar, or
6.2.4 Free Abrasive Machine, using abrasive grit in
cementpasteare,ingeneral,toinvestigatetheeffectsofthetest
lubricant,withsampleholdersrotatingonarotatingtable.This
on the test piece or on one or more of its constituents, to
type of grinding machine greatly increases the speed of
provideexamplesoftheeffectsofaprocess,andtoprovidethe
preparation of finely ground surfaces.
petrographer with visual evidence of examples of reactions in
6.2.5 Polishing Wheel, at least 200 mm [8 in.] in diameter
paste or mortar or concrete of known materials, proportions,
and preferably two-speed, or a vibratory polisher.
age, and history. Specific purposes include:
6.2.6 Hot Plate or Oven, thermostatically controlled, to
5.5.1 To establish whether alkali–silica reaction has taken
permit drying and impregnating specimens with resin or wax
place, what aggregate constituents were affected, what evi-
for preparing thin sections, ground surfaces, and polished
dence of the reaction exists, and what were the effects of the
sections.
reaction on the concrete.
6.2.7 Prospector’s Pick or Bricklayer’s Hammer, or both.
5.5.2 To establish whether one or more alkali–carbonate
6.2.8 Abrasives—Silicon carbide grits, No. 100 (150-µm),
reactions have taken place, which aggregate constituents were
No. 220 (63-µm), No. 320 (31-µm), No. 600 (16-µm), No. 800
affected and what evidence of the reaction or reactions exists,
(12-µm); optical finishing powders, such as M-303, M-204,
and the effects of the reaction on the concrete properties.
M-309; polishing powders as needed.
5.5.3 To establish whether any other cement– aggregate
6.2.9 Plate-glass Squares, 300 to 450 mm [12 to 18 in.] on
reaction has taken place. In addition to alkali–silica and
an edge and at least 10 mm [ ⁄8 in.] thick for hand-finishing
alkali–carbonate reactions, these include hydration of anhy-
specimens.
drous sulfates, rehydration of zeolites, wetting of clays and
6.2.10 Suitable Medium or Media, for impregnating con-
reactions involving solubility, oxidation, sulfates, and sulfides
3 crete and mounting thin sections plus appropriate solvent.
(see Refs (1-3)).
Canada balsam, Lakeside 70 cement, and flexibilized epoxy
5.5.4 To establish whether an aggregate used in a test has
formulations have been used.
been contaminated by a reactive constituent when in fact the
6.2.10.1 Warning—Flexibilized epoxies form strong bonds
aggregate was not reactive.
but have higher indexes of refraction than Canada balsam or
5.5.5 To establish the effects of a freezing and thawing test
Lakeside 70 and are toxic. Do not allow to
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