ASTM C856-95e1

NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
e1
Designation: C 856 – 95
Standard Practice for
Petrographic Examination of Hardened Concrete
This standard is issued under the fixed designation C 856; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
e NOTE—Values for (OH ) within formulas in Table 6 were editorially corrected in September 1999 to (OH) .
6 6
1. Scope
Section
Polarizing Microscope Examination 11
1.1 This practice outlines procedures for the petrographic
Metallographic Microscope Examination 12
examination of samples of hardened concrete. The samples Report 13
examined may be taken from concrete constructions, they may
1.5 The values stated in inch-pound units are to be regarded
be concrete products or portions thereof, or they may be
as the standard. The SI units in parentheses are provided for
concrete or mortar specimens that have been exposed in natural
information purposes only.
environments, or to simulated service conditions, or subjected
1.6 This standard does not purport to address all of the
to laboratory tests. The phrase “concrete constructions” is
safety concerns, if any, associated with its use. It is the
intended to include all sorts of objects, units, or structures that
responsibility of the user of this standard to establish appro-
have been built of hydraulic cement concrete.
priate safety and health practices and determine the applica-
NOTE 1—A photographic chart of materials, phenomena, and reaction
bility of regulatory limitations prior to use. A specific hazard
products discussed in Sections 7-12 and Tables 1-6 are available as
statement is given in 5.2.10.1.
Adjunct C856.
2. Referenced Documents
1.2 The petrographic procedures outlined herein are appli-
cable to the examination of samples of all types of hardened
2.1 ASTM Standards:
hydraulic-cement mixtures, including concrete, mortar, grout,
C 42 Test Method for Obtaining and Testing Drilled Cores
plaster, stucco, terrazzo, and the like. In this practice, the
and Sawed Beams of Concrete
material for examination is designated as “concrete,” even
C 215 Test Method for Fundamental Transverse, Longitu-
though the commentary may be applicable to the other mix-
dinal, and Torsional Frequencies of Concrete Specimens
tures, unless the reference is specifically to media other than
C 227 Test Method for Potential Alkali Reactivity of
concrete.
Cement-Aggregate Combinations (Mortar-Bar Method)
1.3 Annex A1 outlines an uranyl acetate method for identi-
C 294 Descriptive Nomenclature of Constituents of Natural
fying locations where alkali-silica gel may be present. It is a
Mineral Aggregates
requirement that the substances in those locations must be
C 295 Guide for Petrographic Examination of Aggregates
identified using any other more definitive techniques, such as
for Concrete
petrographic microscopy.
C 342 Test Method for Potential Volume Change of
1.4 The purposes of and procedures for petrographic exami-
Cement-Aggregate Combinations
nation of hardened concrete are given in the following sections:
C 441 Test Method for Effectiveness of Mineral Admixtures
Section
or Ground Blast-Furnace Slag in Preventing Excessive
Expansion of Concrete Due to the Alkali-Silica Reaction
Qualifications of Petrographers 3
C 452 Test Method for Potential Expansion of Portland
Purposes of Examination 4
Apparatus 5
Cement Mortars Exposed to Sulfate
Selection and Use of Apparatus 6
C 457 Practice for Microscopical Determination of Air-Void
Samples 7
Content and Parameters of the Air-Void System in Hard-
Examination of Samples 8
Specimen Preparation 9
ened Concrete
Visual and Stereomicroscope Examination 10
C 496 Test Method for Splitting Tensile Strength of Cylin-
drical Concrete Specimens
C 597 Test Method for Pulse Velocity Through Concrete
This practice is under the jurisdiction of ASTM Committee C09 on Concrete
and Concrete Aggregatesand is the direct responsibility of Subcommittee C09.65on
Petrography.
Current edition approved Dec. 10, 1995. Published March 1996. Originally Annual Book of ASTM Standards, Vol 04.02.
1 3
published as C 856 – 77. Last previous edition C 856 – 83 (1998)e . Annual Book of ASTM Standards, Vol 04.01.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
e1
C856–95
TABLE 1 Visual Examination of Concrete (1)
Coarse Aggregate + Fine Aggregate + Matrix + Air + Embedded Items
Composition:
A
Maximum dimension, in. or
mm, in the range> d>
Type: Type: color, by comparison with more than 3 % of total, Type, size, location;
National Research kinds of metal; other
Council Rock Color items
Chart (1963)
1 Gravel 1 Natural sand predominantly in spherical
2 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 nonspherical
5 Mixed 1 + /or 2 + /or 4 5 Mixed 1 + /or 2 + /or 4 3 gradational changes voids?
If Type 1, 2, or 4, homogeneous If Type 1, 2, or 4, color differences between
or heterogeneous homogeneous or voids and mortar?
heterogeneous
Lithologic types voids empty, filled, lined, or
Coarse aggregate more than 20, partly filled
30, 40, or 50 % of total
Fabric:
Shape distribution distribution shape voids below horizontal
particle shape
Distribution as per- distribution or low-angle
grading
Packing 6 ceptible grading (as perceptible) reinforcement
preferred orientation
Grading (even, uneven, parallelism of long axes of
excess, or deficiency of irregular voids or sheets
size or sizes) of voids: with each other;
Parallelism of flat sides or with flat sides or long
long axes of exposed axes of coarse aggregate
sections, normal to
direction of placement
+ /or parallel to formed and
B
finished surfaces
Condition: clean or corroded?
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? Are cracks associated
Through or around coarse aggregate? With cores or sawed specimens, did the aggregate tear in drilling or sawing? Crack fillings? with embedded
Surface deposits? If air dry, are there unusually wet or dry looking areas? Rims on aggregate? items?
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 rodding close to the form. Sections sawed
in the plane of bedding (normal to the direction of placement) are likely to have inconspicuous orientation. Sections broken normal to placement in conventionally placed
concrete 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.
C 637 Specification for Aggregates for Radiation-Shielding Adjunct C856 A chart of 27 photos
Concrete
3. Qualifications of Petrographers
C 638 Descriptive Nomenclature of Constituents of Aggre-
gates for Radiation-Shielding Concrete 3.1 The examination should be performed by persons quali-
C 803 Test Method for Penetration Resistance of Hardened fied by education and experience to operate the equipment used
Concrete and to record and interpret the results obtained. In some cases,
C 805 Test Method for Rebound Number of Hardened the petrographer will have had experience adequate to provide
Concrete detailed interpretation of the materials’ performance with
C 823 Practice for Examination and Sampling of Hardened respect to engineering and other consequences of the observa-
tions. In others, the interpretation will be made in part by
Concrete in Constructions
C 944 Test Method for Abrasion Resistance of Concrete or engineers, scientists, or others qualified to relate the observa-
tions to the questions to be answered.
Mortar Surfaces by the Rotating Cutter Method
C 1012 Test Method for Length Change of Hydraulic- 3.2 This practice may be used by a petrographer employed
directly by those for whom the examination is made. The
Cement Mortars Exposed to a Sulfate Solution
C 1260 Test Method for Potential Alkali Reactivity of employer should tell the petrographer, in as much detail as
necessary, the purposes and objectives of the examination, the
Aggregates (Mortar-Bar Method)
E 3 Methods of Preparation of Metallographic Specimens kind of information needed, and the extent of examination
desired. Pertinent background information, including results of
E 883 Practice for Metallographic Photomicrography
2.2 ASTM Adjuncts: prior testing, should be made available. If the petrographer is
highly experienced, his advice and judgment should be sought
Annual Book of ASTM Standards, Vol 03.01.
Available from ASTM Headquarters, 100 Barr Harbor Drive, West Consho-
hocken, PA 19428. Request Adjunct No. ADJC0856.
NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
e1
C856–95
TABLE 2 Outline for Examination of Concrete with a Stereomicroscope (1)
NOTE 1—Condition—When it is examined at 6 to 103 under good light, the freshly broken surface of a concrete in good physical condition that still
A
retains most of its natural moisture content has a luster that in mineralogical terms is subtranslucent glimmering vitreous. Thin edges of splinters of the
paste 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 less
intense. Concrete in less good physical condition is more opaque on a freshly broken surface, and the luster is dull, subvitreous going toward chalky. A
properly cured laboratory specimen from a concrete mixture of normal proportions cured 28 days that has shown normal compressive or flexural strength
and 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 concrete
in good physical condition.
Under the same conditions of examination, when there is reasonable assurance that the concrete does not contain white portland cement or slag cement,
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 Voids
Lithologic types and mineralogy as percep- Lithologic types and miner Color Grading
tible alogy as perceptible Fracture around or through aggregate Proportion of spherical to nonspherical
Surface texture Shape Contact of matrix with aggregate: Nonspherical, ellipsoidal, irregular, disk-
Within the piece: Surface texture close, no opening visible on sawed shaped
Grain shape Grading or broken surface; aggregate not Color change from interior surface to
Grain size extreme range observed, mm Distribution dislodged with fingers or probe; matrix
Median within range _ to _ mm boundary openings frequent, Interior surface luster like rest of ma-
Textureless (too fine to resolve) common, rare trix, dull, shining
Uniform 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
B
Porosity and absorption Cracks present, absent, result of spec lets, gel, other
If 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, abundant
C
If boundary voids, along what kind of Mineral admixtures
aggregate? All? All of one kind? More Contamination
than 50 % of one kind? Several kinds? Bleeding
Segregation
A
Dana, E. S., Textbook of Mineralogy, revised by W. E. Ford, John Wiley & Sons, New York, N. Y. 4th ed., 1932, pp. 273–274.
B
Pore visible to the naked eye, or at 3 _, or sucks in water that is dropped on it.
C
Dark solid spheres or hollow-centered spheres of glass, or of magnetite, or some of glass and some of magnetite, recognizable at magnification of 3 9 on sawed or
broken surfaces. Other mineral admixtures with characteristic particles visible at low magnification are recognizable. Ground surface of concrete containing portland
blast-furnace slag cement are unusually white near-free surfaces but retain greenish or blue-greenish patches, and slag particles can be seen with the stereomicroscope
or polarizing microscope.
regarding the extent of the examination, and the matters 4.2.5 Description of the cementitious matrix, including
discussed in 3.3. qualitative determination of the kind of hydraulic binder used,
3.3 This practice may form the basis for establishing ar- degree of hydration, degree of carbonation if present, evidence
rangements between a purchaser of a consulting service and the of unsoundness of the cement, presence of a mineral admix-
consultant. In such a case, the purchaser and the consultant ture, the nature of the hydration products, adequacy of curing,
should together determine the kind, extent, and objectives of and unusually high water - cement ratio of the paste.
the examination and analyses to be made, and should record
4.2.6 Determination whether alkali - silica or alkali - car-
their agreement in writing. The agreement may stipulate
bonate reactions, or cement - aggregate reactions, or reactions
specific determinations to be made, observations to be re-
between contaminants and the matrix have taken place, and
ported, funds to be obligated, or a combination of these or other
their effects upon the concrete.
conditions.
4.2.7 Determination whether the concrete has been sub-
jected to and affected by sulfate attack, or other chemical
4. Purposes of Examination
attack, or early freezing, or to other harmful effects of freezing
4.1 Examples of purposes for which petrographic examina-
and thawing.
tion of concrete is used are given in 4.2-4.5. The probable
4.2.8 Part of a survey of the safety of a structure for a
usefulness of petrographic examination in specific instances
present or proposed use.
may be determined by discussion with an experienced petrog-
4.2.9 Determination whether concrete subjected to fire is
rapher of the objectives of the investigation proposed or
essentially undamaged or moder
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