ASTM C295 – Standard Guide for Petrographic Examination of Aggregates for Concrete
This ASTM outlines test methods for petrographic examination on sand and gravel proposed for
use in cementitious mixtures or as raw materials placed as fill beneath roads, building
foundations, and various flatwork (parking areas, driveways, sidewalks, patios, etc.).
Petrographic examinations of sand and gravel can be made for the following reasons (and more):
to determine physical and chemical characteristics, classify and describe constituents, determine
relative amounts of constituents, comparison of new sources with existing sources that have
performance records, identify kind and extent of unstable minerals, identify portion of sample
especially susceptible to freeze-thaw damage, determine proportions of different particle shapes
(cubic, flat, elongated, etc.), identify possible contaminants in sample including glass, cinders,
soil, rotten vegetation, etc., and identify potential alkali-silica reactive (ASR) and alkali-
carbonate reactive (ACR) constituents.
Our client’s purpose will determine the specific methods used to examine the sample of sand and
gravel. Typically, the study begins with an overall look by using the naked eye to note general
composition and condition. Selected particles are more closely examined with a stereo-
microscope at 10 to 80 magnifications to confirm composition and condition. Occasionally, a
closer examination is required to adequately describe the sample and a polarizing microscope is
used to do a thin-section analysis (50 to 1000 magnification (selected particles are bound in clear
epoxy and very thin transparent slices made and placed between glass sides).
use in cementitious mixtures or as raw materials placed as fill beneath roads, building
foundations, and various flatwork (parking areas, driveways, sidewalks, patios, etc.).
Petrographic examinations of sand and gravel can be made for the following reasons (and more):
to determine physical and chemical characteristics, classify and describe constituents, determine
relative amounts of constituents, comparison of new sources with existing sources that have
performance records, identify kind and extent of unstable minerals, identify portion of sample
especially susceptible to freeze-thaw damage, determine proportions of different particle shapes
(cubic, flat, elongated, etc.), identify possible contaminants in sample including glass, cinders,
soil, rotten vegetation, etc., and identify potential alkali-silica reactive (ASR) and alkali-
carbonate reactive (ACR) constituents.
Our client’s purpose will determine the specific methods used to examine the sample of sand and
gravel. Typically, the study begins with an overall look by using the naked eye to note general
composition and condition. Selected particles are more closely examined with a stereo-
microscope at 10 to 80 magnifications to confirm composition and condition. Occasionally, a
closer examination is required to adequately describe the sample and a polarizing microscope is
used to do a thin-section analysis (50 to 1000 magnification (selected particles are bound in clear
epoxy and very thin transparent slices made and placed between glass sides).
Gravel as received for examination and testing.
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Thin-section of gravel shows details of mineral composition in this basalt.
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ASTM C457 – Standard Test Method for the Determination of Parameters of the Air-Void System in Hardened Concrete
This ASTM describes methods for microscopical determination of total air content and when
requested specific surface, spacing factor, and other parameters. We use the Modified Point-
Count Method that begins by sawing sample to expose a representative surface (typically
longitudinal). This surface is then ground flat and polished to properly expose the air-voids for
observation. The polished surface is then placed in a two-way stage and moved in a regular grid
system of points at which calibrated stops are made and on either an air-void, aggregate particle,
or the hardened paste. From this data the air content and various parameters are calculated. This
test method is typically used to determine the susceptibility of the material to freeze-thaw
damage and comparison to project specifications.
requested specific surface, spacing factor, and other parameters. We use the Modified Point-
Count Method that begins by sawing sample to expose a representative surface (typically
longitudinal). This surface is then ground flat and polished to properly expose the air-voids for
observation. The polished surface is then placed in a two-way stage and moved in a regular grid
system of points at which calibrated stops are made and on either an air-void, aggregate particle,
or the hardened paste. From this data the air content and various parameters are calculated. This
test method is typically used to determine the susceptibility of the material to freeze-thaw
damage and comparison to project specifications.
A concrete core as received for ASTM C457 testing.
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Polished surface of longitudinally sawn core ready for ASTM C457 examination. Some air-voids (V) and aggregate (A) are marked.
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ASTM C856 - STANDARD PRACTICE FOR PETROGRAPHIC EXAMINATION OF HARDENED CONCRETE
A general petrographic examination to determine concrete condition consists of studying sample(s) as received with the unaided eye and a hand lens to note prominent features including cracks, voids, aggregate segregation, zones of paste discoloration and erosion, etc. Concrete is than sawn at pre-determined locations to obtain surfaces for lapping, which typically consists of a series of abrasives that include No. 220, 600 and 800 grit sizes. Lapped surface(s) are studied and photographed using a stereo-zoom microscope at 10 to 80 magnification to note micro-cracking, voids, aggregate characteristics, etc.
Specific areas for more detailed examination are noted and thin-sections prepared and studied/photographed using a polarizing microscope at 50 to 400 magnification noting fine micro-cracking, degree of cementitious materials hydration and type, any paste alteration including carbonation, etc. Report lists sample(s) source and location, available history including mix design, results of physical and chemical tests and interpretation of test results as they relate to success or failure of the concrete. Any additional testing, such as XRD, SEM, etc., that would help to evaluate the condition of the concrete is also recommended.
Specific areas for more detailed examination are noted and thin-sections prepared and studied/photographed using a polarizing microscope at 50 to 400 magnification noting fine micro-cracking, degree of cementitious materials hydration and type, any paste alteration including carbonation, etc. Report lists sample(s) source and location, available history including mix design, results of physical and chemical tests and interpretation of test results as they relate to success or failure of the concrete. Any additional testing, such as XRD, SEM, etc., that would help to evaluate the condition of the concrete is also recommended.
Cores received for ASTM C856 examination adjacent to their related epoxy stabilized billets we sawed from a specific part of each core for more detailed study.
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Thin-section analysis using a polarizing microscope to note details of the ASTM C856 examination. Thin-sections fabricated from the above epoxy stabilized billets.
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ASTM C1324 - STANDARD TEST METHOD FOR EXAMINATION AND ANALYSIS OF HARDENED MASONRY MORTAR
This test method provides procedures for petrographic examination and chemical analysis for the components. After hearing our client’s concerns, we decide if the petrographic only, chemical analysis only or both parts are necessary to address the expressed concerns. Petrographic examination consists of logging-in and placing sample(s) in a stainless- steel tray(s) marked with a project number followed by measuring and photographing. Sample(s) are than studied with the unaided eye and a stereo-zoom microscope at 5 to 80 magnification to note prominent features including cracks, voids, sand segregation, zones of paste discoloration, reinforcement embedment (stucco), coat thicknesses, etc. Sample(s) are than sawn at pre-determined locations to obtain surfaces for lapping, which typically consist of a series of abrasives that include No. 220, 600 and 800 grit sizes.
Lapped surface(s) are studied and photographed using a stereo-zoom microscope at 10 to 80 magnification to note micro-cracking, voids, sand characteristics, etc. Specific areas for more detailed examination are noted and thin-sections prepared and studied/photographed using a polarizing microscope at 50 to 400 magnification noting fine micro-cracking, degree of cementitious materials hydration and type, any paste alteration including carbonation, estimated proportions, etc. Report lists sample(s) source and location, available history including mix type, results of observations and interpretation of test results. Any additional testing, such as XRD, SEM, etc., that would help to evaluate the condition of the mortar is also recommended.
Lapped surface(s) are studied and photographed using a stereo-zoom microscope at 10 to 80 magnification to note micro-cracking, voids, sand characteristics, etc. Specific areas for more detailed examination are noted and thin-sections prepared and studied/photographed using a polarizing microscope at 50 to 400 magnification noting fine micro-cracking, degree of cementitious materials hydration and type, any paste alteration including carbonation, estimated proportions, etc. Report lists sample(s) source and location, available history including mix type, results of observations and interpretation of test results. Any additional testing, such as XRD, SEM, etc., that would help to evaluate the condition of the mortar is also recommended.
Samples of historic mortar and unknown black substance received for ASTM C1324 and SEM-FTIR testing.
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Thin-section analysis of the mortar revealed sand composed of quartz (Q), granite (G), feldspar (F), and mafic (M) minerals. Some air-voids (V) and the carbonated paste (CC) are labeled.
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ASTM C1721 - STANDARD GUIDE FOR PETROGRAPHIC EXAMINATION OF DIMENSION STONE
Sample(s) are measured, logged-in, placed in stainless steel trays and
photographed (dry and wet) upon receipt. A hand lens and stereo-zoom microscope (10X to
80X) are used to observe each sample and observations of overall texture/structure, prominent
voids and cracks and other potential weak zones are noted on a datasheet. Typical and non-
typical areas are selected for thin-sectioning.
Thin-section analysis is performed using a polarizing microscope at 50X to 400X under
transmitted and polarized light conditions. Photomicrographs are taken of each significant rock
type and condition and these details are added to the datasheet. Final report contains stone
source(s), proposed use, composition, deleterious minerals, any recommended additional testing,
conclusion and an appendix with tabulated results and photographs/photomicrographs.
photographed (dry and wet) upon receipt. A hand lens and stereo-zoom microscope (10X to
80X) are used to observe each sample and observations of overall texture/structure, prominent
voids and cracks and other potential weak zones are noted on a datasheet. Typical and non-
typical areas are selected for thin-sectioning.
Thin-section analysis is performed using a polarizing microscope at 50X to 400X under
transmitted and polarized light conditions. Photomicrographs are taken of each significant rock
type and condition and these details are added to the datasheet. Final report contains stone
source(s), proposed use, composition, deleterious minerals, any recommended additional testing,
conclusion and an appendix with tabulated results and photographs/photomicrographs.
Sample of dimension stone received for ASTM C1721 examination. Stone proposed for use in a swimming pool.
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Thin-section analysis of the stone revealed that it is Banded Green Onyx with some cracks (arrows).
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ASTM D4992 - STANDARD PRACTICE FOR EVALUATION OF ROCK TO BE USED FOR EROSION CONTROL
Our scope is limited to laboratory petrographic examination of samples. Other
parties perform field visits. Laboratory durability tests including wet-dry, freeze-thaw,
soundness, absorption, etc., when performed, are by other approved laboratories contracted
directly by client and the data furnished to us.
Rock sample(s) is photographed, logged-in and placed in a stainless-steel tray(s) marked with
project number upon receipt. Rock is than sawn into pre-determined cross-sections to obtain
surfaces for lapping. Lapping typically consists of a series of abrasives that include No. 220, 600
and 800 grit sizes. Features noted on original and lapped surfaces that could potentially affect
durability are studied/photographed using a stereo-zoom microscope at 10 to 80 magnification
and noted on a datasheet. These features include preliminary identification of minerals and rock
type, cracks and crack patterns, degree and kind of weathering, potential zones of weakness and
directional features.
Specific areas for more detailed examination of these features are delineated and thin-sections
prepared and studied/photographed using a polarizing microscope at 50 to 400 magnification.
Report summarizes our petrographic examination results. Undesirable features, if any, are
qualitatively discussed and when possible quantified. Recommendations for any additional
testing are also included.
parties perform field visits. Laboratory durability tests including wet-dry, freeze-thaw,
soundness, absorption, etc., when performed, are by other approved laboratories contracted
directly by client and the data furnished to us.
Rock sample(s) is photographed, logged-in and placed in a stainless-steel tray(s) marked with
project number upon receipt. Rock is than sawn into pre-determined cross-sections to obtain
surfaces for lapping. Lapping typically consists of a series of abrasives that include No. 220, 600
and 800 grit sizes. Features noted on original and lapped surfaces that could potentially affect
durability are studied/photographed using a stereo-zoom microscope at 10 to 80 magnification
and noted on a datasheet. These features include preliminary identification of minerals and rock
type, cracks and crack patterns, degree and kind of weathering, potential zones of weakness and
directional features.
Specific areas for more detailed examination of these features are delineated and thin-sections
prepared and studied/photographed using a polarizing microscope at 50 to 400 magnification.
Report summarizes our petrographic examination results. Undesirable features, if any, are
qualitatively discussed and when possible quantified. Recommendations for any additional
testing are also included.
Quarried rock received for ASTM D4992 examination. Stone proposed for use as rip rap in an erosion control project.
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Thin-section analysis showed sample is altered cracked basalt (AB) with inclusions of metamorphosed rock. A significant amount of chlorite and calcite is also present.
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