ASTM C294-98
(Terminology)Standard Descriptive Nonmenclature for Constituents of Concrete Aggregates
Standard Descriptive Nonmenclature for Constituents of Concrete Aggregates
SCOPE
1.1 This descriptive nomenclature provides brief descriptions of some of the more common, or more important, natural materials of which mineral aggregates are composed (Note 1). The descriptions provide a basis for understanding these terms as used to designate aggregate constituents. Many of the materials described frequently occur in particles that do not display all the characteristics given in the descriptions, and most of these rocks grade from varieties meeting one description to varieties meeting another with all intermediate stages being found. Note 1-These descriptions characterize minerals and rocks as they occur in nature and do not include blast-furnace slag or lightweight aggregates that are prepared by the alteration of the structure and composition of natural material. Blast-furnace slag is defined in Definitions C125. Information about lightweight aggregates is given in Specifications C330, C331, and C332.
1.2 The accurate identification of rocks and minerals can, in many cases, be made only by a qualified geologist, mineralogist, or petrographer using the apparatus and procedures of these sciences. Reference to these descriptions may, however, serve to indicate or prevent gross errors in identification. Identification of the constituent materials in an aggregate may assist in recognizing its properties, but identification alone cannot provide a basis for predicting the behavior of aggregates in service. Mineral aggregates composed of any type or combination of types of rocks and minerals may perform well or poorly in service depending upon the exposure to which they are subjected, the physical and chemical properties of the matrix in which they are embedded, their physical condition at the time they are used, and other factors. Small amounts of minerals or rocks that may occur only as contaminants or accessories in the aggregate may decisively influence its quality.
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Designation: C 294 – 98
Standard Descriptive Nomenclature for
Constituents of Concrete Aggregates
This standard is issued under the fixed designation C 294; 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.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope 3. Significance and Use
1.1 This standard provides brief descriptions of some of the 3.1 This descriptive nomenclature provides information on
more commonly occurring, or more important, natural and terms commonly applied to concrete aggregates. This standard
artificial materials of which mineral aggregates are composed. is intended to assist in understanding the meaning and signifi-
The descriptions provide a basis for understanding these terms cance of the terms.
as applied to concrete aggregates. When appropriate, brief 3.2 Many of the materials described frequently occur in
observations regarding the potential effects of using the natural particles that do not display all the characteristics given in the
and artificial materials in concrete are discussed. descriptions, and most of the described rocks grade from
varieties meeting one description to varieties meeting another
NOTE 1—These descriptions characterize minerals and rocks as they
with all intermediate stages being found.
occur in nature and blast-furnace slag or lightweight aggregates that are
3.3 The accurate identification of rocks and minerals can, in
prepared by the alteration of the structure and composition of natural
many cases, be made only by a qualified geologist, mineralo-
material. Information about lightweight aggregates are given in Specifi-
cations C 330, C 331, and C 332.
gist, or petrographer using the apparatus and procedures of
these sciences. Reference to these descriptions may, however,
1.2 This standard does not include descriptions of constitu-
serve to indicate or prevent gross errors in identification.
ents of aggregates used in radiation shielding concrete. See
Identification of the constituent materials in an aggregate may
ASTM C 638.
assist in characterizing its engineering properties, but identifi-
2. Referenced Documents
cation alone cannot provide the sole basis for predicting
behavior of aggregates in service. Aggregates of any type or
2.1 ASTM Standards:
combination of types may perform well or poorly in service
C 125 Terminology Relating to Concrete and Concrete
depending upon the exposure to which the concrete is sub-
Aggregates
jected, the physical and chemical properties of the matrix in
C 227 Test Method for Potential Alkali Reactivity of Ce-
which they are embedded, their physical condition at the time
ment & Aggregate Combinations (Mortar Bar Method)
they are used, and other factors. Constituents that may occur
C 289 Test Method for Potential Reactivity of Aggregates
only in minor amounts in the aggregate may or may not
(Chemical Method)
decisively influence its performance. Information about con-
C 330 Specification for Lightweight Aggregates for Struc-
crete aggregate performance in concrete has been published by
tural Concrete
ASTM.
C 331 Specification for Lightweight Aggregates for Con-
crete Masonry Units
CONSTITUENTS OF NATURAL MINERAL
C 332 Specification for Lightweight Aggregates for Insulat-
AGGREGATES
ing Concrete
C 638 Constituents of Aggregates for Radiation-Shielding
4. Classes and Types
Concrete
4.1 The materials found as constituents of natural mineral
aggregates are rocks and minerals.
4.2 Minerals are naturally occurring inorganic substances of
This descriptive nomenclature is under the jurisdiction of ASTM Committee
C-9 on Concrete and Concrete Aggregates and is the direct responsibility of
more or less definite chemical composition and usually of a
Subcommittee C09.65 on Petrography of Concrete and Aggregates.
specific crystalline structure. Most rocks are composed of
Current edition approved August 10, 1998. Published March 1999. Originally
e1
published as C 294 – 52. Last previous edition C 294 – 86 (1991) .
This standard has been extensively revised. The reader should compare this
edition with the last previous edition for exact revisions. Klieger, P., and Lamond, J. F., editors, Significance of Tests and Properties of
Annual Book of ASTM Standards, Vol 04.02. Concrete and Concrete-Making Materials, ASTM STP 169C, 1994.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
C294–98
several minerals but some are composed of only one mineral. the rock chert and is potentially deleteriously reactive with the
Certain examples of the rock quartzite are composed exclu- alkalies in hydraulic cement paste.
sively of the mineral quartz, and certain limestones are
5.4 Tridymite and cristobalite—high temperature crystal-
composed exclusively of the mineral calcite. Individual sand
line forms of silica (SiO ) sometimes found in volcanic rocks.
grains frequently are composed of particles of rock, but they
They are metastable at ordinary temperatures and pressures.
may be composed of a single mineral, particularly in the finer
They are rare minerals in aggregates except in areas where
sizes.
volcanic rocks are abundant. A type of cristobalite is a common
4.3 Rocks are classified according to origin into three major
constituent of opal. Tridymite and cristobalite are potentially
divisions: igneous, sedimentary, and metamorphic. These three
deleteriously reactive with the alkalies in hydraulic cement
major groups are subdivided into types according to mineral
paste.
and chemical composition, texture, and internal structure.
4.3.1 Igneous rocks form from molten matter either at or
6. Feldspars
below the earth’s surface.
4.3.2 Sedimentary rocks form near the earth’s surface by the 6.1 The minerals of the feldspar group are the most abun-
accumulation and consolidation of the products of weathering
dant rock-forming minerals in the crust of the earth. They are
and erosion of existing rocks, or by direct chemical precipita-
important constituents of all three major rock groups, igneous,
tion. Sedimentary rocks may form from pre-existing igneous,
sedimentary, and metamorphic. Since all feldspars have good
metamorphic, or sedimentary rocks.
cleavages in two directions, particles of feldspar usually show
4.3.3 Metamorphic rocks form from pre-existing igneous,
several smooth surfaces. Frequently, the smooth cleavage
sedimentary, or metamorphic rocks by the action of heat or
surfaces show fine parallel lines. All feldspars are slightly less
pressure or both.
hard than, and can be scratched by, quartz and will, when fresh,
easily scratch a penny. The various members of the group are
5. Silica Minerals
differentiated by chemical composition and crystallographic
5.1 Quartz—a very common hard mineral composed of
properties. The feldspars orthoclase, sanidine, and microcline
silica (SiO ). It will scratch glass and is not scratched by a
are potassium aluminum silicates, and are frequently referred
knife. When pure it is colorless with a glassy (vitreous) luster
to as potassium feldspars. The plagioclase feldspars include
and a shell-like (conchoidal) fracture. It lacks a visible cleav-
those that are sodium aluminum silicates and calcium alumi-
age (the ability to break in definite directions along even
num silicates, or both sodium and calcium aluminum silicates.
planes) and, when present in massive rocks such as granite, it
This group, frequently referred to as the “soda-lime” group,
usually has no characteristic shape. It is resistant to weathering
includes a continuous series, of varying chemical composition
and is therefore an important constituent of many sand and
and optical properties, from albite, the sodium aluminum
gravel deposits and many sandstones. It is also abundant in
feldspar, to anorthite, the calcium aluminum feldspar, with
many light-colored igneous and metamorphic rocks. Some
intermediate members of the series designated oligoclase,
strained, or intensely fractured (granulated), and microcrystal-
andesine, labradorite, and bytownite. Potassium feldspars and
line quartz may be potentially deleteriously reactive with the
sodium-rich plagioclase feldspars occur typically in igneous
alkalies in the hydraulic cement paste.
rocks such as granites and rhyolites, whereas, plagioclase
5.2 Opal—a hydrous form of silica (SiO ·nH O) which
2 2
occurs without characteristic external form or internal crystal- feldspars of higher calcium content are found in igneous rocks
line arrangement as determined by ordinary visible light of lower silica content such as diorite, gabbro, andesite, and
methods. When X-ray diffraction methods are used, opal may
basalt.
show some evidences of internal crystalline arrangement. Opal
has a variable water content, generally ranging from 3 to 9 %.
7. Ferromagnesian Minerals
The specific gravity and hardness are always less than those of
7.1 Many igneous and metamorphic rocks contain dark
quartz. The color is variable and the luster is resinous to glassy.
green to black minerals that are generally silicates of iron or
It is usually found in sedimentary rocks, especially some
magnesium, or of both. They include the minerals of the
cherts, and is the principal constituent of diatomite. It is also
amphibole, pyroxene, and olivine groups. The most common
found as a secondary material filling cavities and fissures in
amphibole mineral is hornblende; the most common pyroxene
igneous rocks and may occur as a coating on gravel and sand.
mineral is augite; and the most common olivine mineral is
The recognition of opal in aggregates is important because it is
forsterite. Dark mica, such as biotite and phlogopite, are also
potentially deleteriously reactive with the alkalies in hydraulic
considered ferromagnesian minerals. The amphibole and py-
cement paste or with the alkalies from other sources, such as
roxene minerals are brown to green to black and generally
aggregates containing zeolites, and ground water.
occur as prismatic units. Olivine is usually olive green, glassy
5.3 Chalcedony—chalcedony has been considered both as
in appearance, and usually altered. Biotite has excellent cleav-
a distinct mineral and a variety of quartz. It is frequently
age and can be easily cleaved into thin flakes and plates. These
composed of a mixture of microscopic fibers of quartz with a
minerals can be found as components of a variety of rocks, and
large number of submicroscopic pores filled with water and air.
The properties of chalcedony are intermediate between those of in sands and gravels. Olivine is found only in dark igneous
rocks where quartz is not present, and in sands and gravels
opal and quartz, from which it can sometimes be distinguished
only by laboratory tests. It frequently occurs as a constituent of close to the olivine source.
C294–98
8. Micaceous Minerals 10. Zeolites
10.1 The zeolite minerals are a large group of hydrated
8.1 Micaceous minerals have perfect cleavage in one direc-
aluminum silicates of the alkali and alkaline earth elements
tion and can be easily split into thin flakes. The mica minerals
which are soft and usually white or light colored. They are
of the muscovite group are colorless to light green; of the
formed as a secondary filling in cavities or fissures in igneous
biotite group, dark brown to black or dark green; of the
rocks, or within the rock itself as a product of hydrothermal
lepidolite group, white to pink and red or yellow; and of the
alteration of original minerals, especially feldspars. Some
chlorite group, shades of green. Another mica, phlogopite, is
zeolites, particularly heulandite, natrolite, and laumontite,
similar to biotite, commonly has a pearl-like luster and bronze
reportedly produce deleterious effects in concrete, the first two
color, and less commonly is brownish red, green, or yellow.
having been reported to raise the alkali content in concrete by
The mica minerals are common and occur in igneous, sedi-
releasing alkalies through cation exchange and thus increasing
mentary, and metamorphic rocks, and are common as minor to
alkali reactivity when alkali-reactive aggregate constituents are
trace components in many sands and gravels. The muscovite,
present. Laumontite and its partially dehydrated variety leon-
biotite, lepidolite, and phlogopite minerals cleave into flakes
hardite are notable for their substantial volume change with
and plates that are elastic; the chlorite minerals, by comparison,
wetting and drying. Both are found in rocks such as quartz
form in elastic flakes and plates. Vermiculite (a mica-like
diorites and some sandstones.
mineral) forms by the alteration of other micas and is brown
and has a bronze luster.
11. Carbonate Minerals
11.1 The most common carbonate mineral is calcite (cal-
9. Clay Minerals
cium carbonate, CaCO ). The mineral dolomite consists of
calcium carbonate and magnesium carbonate (CaCO ·MgCO
9.1 The term “clay” refers to natural material composed of
3 3
or CaMg(CO ) ) in equivalent molecular amounts, which are
particles in a specific size range less than 2 μm (0.002 mm).
3 2
54.27 and 45.73 by mass %, respectively. Both calcite and
Mineralogically, clay refers to a group of layered silicate
dolomite are relatively soft, the hardness of calcite being 3 and
minerals including the clay-micas (illites), the kaolin group,
that of dolomite 3 ⁄2 to 4 on the Mohs scale, and are readily
very finely divided chlorites, and the swelling clays—smectite
scratched by a knife blade. They have rhombohedral cleavage,
including montmorillonites. Members of several groups, par-
which results in their breaking into fragments with smooth
ticularly micas, chlorites, and vermiculites, occur both in the
parallelogram shaped sides. Calcite is soluble with vigorous
clay-size range and in larger sizes. Some clays are made up of
effervescence in cold dilute hydrochloric acid; dolomite is
alternating layers of two or more clay groups. Random, regular,
soluble with slow effervescence in cold dilute hydrochloric
or both types of interlayering are known. If smectite is a
acid and with vigorous effervescence if the acid or the sample
significant constituent in such mixtures, then fairly large
is heated or if the sample is pulverized.
volume changes may occur with wetting and drying.
9.2 Clay minerals are hydrous aluminum, magnesium, and
12. Sulfate Minerals
iron silicates that may contain calcium, magnesium, potassium,
12.1 Carbonate rocks and shales may contain
...
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