1、Designation: C 294 05Standard Descriptive Nomenclature forConstituents of Concrete Aggregates1This standard is issued under the fixed designation C 294; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A n
2、umber in parentheses indicates the year of last reapproval. Asuperscript 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. Scope1.1 This descriptive nomenclature provides brief descrip-t
3、ions of some of the more commonly occurring, or moreimportant, natural and artificial materials of which mineralaggregates are composed. The descriptions provide a basis forunderstanding these terms as applied to concrete aggregates.When appropriate, brief observations regarding the potentialeffects
4、 of using the natural and artificial materials in concreteare discussed.NOTE 1These descriptions characterize minerals and rocks as theyoccur in nature and blast-furnace slag or lightweight aggregates that areprepared by the alteration of the structure and composition of naturalmaterial. Information
5、 about lightweight aggregates are given in Specifi-cations C 330, C 331, and C 332.1.2 This standard does not include descriptions of constitu-ents of aggregates used in radiation shielding concrete. SeeDescriptive Nonmenclature C 638.2. Referenced Documents2.1 ASTM Standards:2C 125 Terminology Rela
6、ting to Concrete and ConcreteAggregatesC 227 Test Method for Potential Alkali Reactivity ofCement-Aggregate Combinations (Mortar Bar Method)C 289 Test Method for Potential Alkali-Silica Reactivity ofAggregates (Chemical Method)C 330 Specification for Lightweight Aggregates for Struc-tural ConcreteC
7、331 Specification for Lightweight Aggregates for Con-crete Masonry UnitsC 332 Specification for Lightweight Aggregates for Insulat-ing ConcreteC 638 Descriptive Nonmenclature of Constituents of Ag-gregates for Radiation-Shielding Concrete3. Significance and Use3.1 This descriptive nomenclature provi
8、des information onterms commonly applied to concrete aggregates. This standardis intended to assist in understanding the meaning and signifi-cance of the terms.3.2 Many of the materials described frequently occur inparticles that do not display all the characteristics given in thedescriptions, and m
9、ost of the described rocks grade fromvarieties meeting one description to varieties meeting anotherwith all intermediate stages being found.3.3 The accurate identification of rocks and minerals can, inmany cases, be made only by a qualified geologist, mineralo-gist, or petrographer using the apparat
10、us and procedures ofthese sciences. Reference to these descriptions may, however,serve to indicate or prevent gross errors in identification.Identification of the constituent materials in an aggregate mayassist in characterizing its engineering properties, but identifi-cation alone cannot provide th
11、e sole basis for predictingbehavior of aggregates in service. Aggregates of any type orcombination of types may perform well or poorly in servicedepending upon the exposure to which the concrete is sub-jected, the physical and chemical properties of the matrix inwhich they are embedded, their physic
12、al condition at the timethey are used, and other factors. Constituents that may occuronly in minor amounts in the aggregate may or may notdecisively influence its performance. Information about con-crete aggregate performance in concrete has been published byASTM.3CONSTITUENTS OF NATURAL MINERALAGGR
13、EGATES4. Classes and Types4.1 The materials found as constituents of natural mineralaggregates are minerals and rocks.4.2 Minerals are naturally occurring inorganic substances ofmore or less definite chemical composition and usually of aspecific crystalline structure. The physical nature of the rock
14、-forming minerals and aspects of crystal chemistry determinethe important physical and chemical properties of natural1This descriptive nomenclature is under the jurisdiction of ASTM CommitteeC09 on Concrete and Concrete Aggregates and is the direct responsibility ofSubcommittee C09.65 on Petrography
15、.Current edition approved Jan. 1, 2005. Published January 2005. Originallyapproved in 1952. Last previous edition approved in 2004 as C 294 04.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards vo
16、lume information, refer to the standards Document Summary page onthe ASTM website.3Klieger, P., and Lamond, J. F., editors, Significance of Tests and Properties ofConcrete and Concrete-Making Materials, ASTM STP 169C, 1994.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Consh
17、ohocken, PA 19428-2959, United States.mineral aggregates. Certain assemblages of rock-forming min-erals possess desirable qualities for use as aggregates incementitious materials.4.2.1 Minerals are characterized by their crystallographic,physical, and optical properties and their chemical composi-ti
18、on. The crystallographic properties of minerals may bedetermined by x-ray diffraction and optical properties (1-6).The physical properties of minerals include but are not limitedto crystal habit, cleavage, parting, fracture, hardness, specificgravity, luster, color, streak, magnetism, luminescence,
19、andpyroelectricity (7). The optical properties of minerals includebut are not limited to refractive index, birefringence, optic sign,pleochroism, and sign of elongation (2-5). Methods to deter-mine the chemical composition of minerals include but are notlimited to optical properties (5), flame photo
20、metry (7,8),chemical spot tests (9,10), various staining techniques (11),x-ray fluorescence, and electron microscopy (12-14).4.2.2 Different minerals may have the same chemical com-position but different crystallographic and physical properties.Such sets of minerals are known as polymorphs. Distingu
21、ish-ing between some polymorphs can be important for determin-ing the suitability of aggregates for use in cementitiousmaterials.4.3 Rocks are classified according to origin into three majordivisions: igneous, sedimentary, and metamorphic. These threemajor groups are subdivided into types according
22、to mineraland chemical composition, texture, and internal structure. Mostrocks are composed of several minerals but some are composedof only one mineral. Certain examples of the rock quartzite arecomposed exclusively of the mineral quartz, and certainlimestones are composed exclusively of the minera
23、l calcite.Individual sand grains frequently are composed of particles ofrock, but they may be composed of a single mineral, particu-larly in the finer sizes.4.3.1 Igneous rocks form from molten matter either at orbelow the earths surface.4.3.2 Sedimentary rocks form near the earths surface by theacc
24、umulation and consolidation of the products of weatheringand erosion of existing rocks, or by direct chemical precipita-tion. Sedimentary rocks may form from pre-existing igneous,metamorphic, or sedimentary rocks.4.3.3 Metamorphic rocks form from pre-existing igneous,sedimentary, or metamorphic rock
25、s by the action of heat orpressure or both.5. Silica Minerals5.1 Quartza very common hard mineral composed ofsilica (SiO2). It will scratch glass and is not scratched by aknife. When pure it is colorless with a glassy (vitreous) lusterand a shell-like (conchoidal) fracture. It lacks a visible cleav-
26、age (the ability to break in definite directions along evenplanes) and, when present in massive rocks such as granite, itusually has no characteristic shape. It is resistant to weatheringand is therefore an important constituent of many sand andgravel deposits and many sandstones. It is also abundan
27、t inmany light-colored igneous and metamorphic rocks. Somestrained, or intensely fractured (granulated), and microcrystal-line quartz may be potentially deleteriously reactive with thealkalies in the hydraulic cement paste.5.2 Opala hydrous form of silica (SiO2 nH2O) whichoccurs without characterist
28、ic external form or internal crystal-line arrangement as determined by ordinary visible lightmethods. When X-ray diffraction methods are used, opal mayshow some evidences of internal crystalline arrangement. Opalhas a variable water content, generally ranging from 3 to 9 %.The specific gravity and h
29、ardness are always less than those ofquartz. The color is variable and the luster is resinous to glassy.It is usually found in sedimentary rocks, especially somecherts, and is the principal constituent of diatomite. It is alsofound as a secondary material filling cavities and fissures inigneous rock
30、s and may occur as a coating on gravel and sand.The recognition of opal in aggregates is important because it ispotentially deleteriously reactive with the alkalies in hydrauliccement paste or with the alkalies from other sources, such asaggregates containing zeolites, and ground water.5.3 Chalcedon
31、ychalcedony has been considered both as adistinct mineral and a variety of quartz. It is frequentlycomposed of a mixture of microscopic fibers of quartz with alarge number of submicroscopic pores filled with water and air.The properties of chalcedony are intermediate between those ofopal and quartz,
32、 from which it can sometimes be distinguishedonly by laboratory tests. It frequently occurs as a constituent ofthe rock chert and is potentially deleteriously reactive with thealkalies in hydraulic cement paste.5.4 Tridymite and cristobalitehigh temperature crystallineforms of silica (SiO2) sometime
33、s found in volcanic rocks. Theyare metastable at ordinary temperatures and pressures. They arerare minerals in aggregates except in areas where volcanicrocks are abundant. A type of cristobalite is a commonconstituent of opal. Tridymite and cristobalite are potentiallydeleteriously reactive with the
34、 alkalies in hydraulic cementpaste.6. Feldspars6.1 The minerals of the feldspar group are the most abun-dant rock-forming minerals in the crust of the earth. They areimportant constituents of all three major rock groups, igneous,sedimentary, and metamorphic. Since all feldspars have goodcleavages in
35、 two directions, particles of feldspar usually showseveral smooth surfaces. Frequently, the smooth cleavagesurfaces show fine parallel lines. All feldspars are slightly lesshard than, and can be scratched by, quartz and will, when fresh,easily scratch a penny. The various members of the group aredif
36、ferentiated by chemical composition and crystallographicproperties. The feldspars orthoclase, sanidine, and microclineare potassium aluminum silicates, and are frequently referredto as potassium feldspars. The plagioclase feldspars includethose that are sodium aluminum silicates and calcium alumi-nu
37、m silicates, or both sodium and calcium aluminum silicates.This group, frequently referred to as the “soda-lime” group,includes a continuous series, of varying chemical compositionand optical properties, from albite, the sodium aluminumfeldspar, to anorthite, the calcium aluminum feldspar, withinter
38、mediate members of the series designated oligoclase,andesine, labradorite, and bytownite. Potassium feldspars andsodium-rich plagioclase feldspars occur typically in igneousrocks such as granites and rhyolites, whereas, plagioclaseC294052feldspars of higher calcium content are found in igneous rocks
39、of lower silica content such as diorite, gabbro, andesite, andbasalt.7. Ferromagnesian Minerals7.1 Many igneous and metamorphic rocks contain darkgreen to black minerals that are generally silicates of iron ormagnesium, or of both. They include the minerals of theamphibole, pyroxene, and olivine gro
40、ups. The most commonamphibole mineral is hornblende; the most common pyroxenemineral is augite; and the most common olivine mineral isforsterite. Dark mica, such as biotite and phlogopite, are alsoconsidered ferromagnesian minerals. The amphibole and py-roxene minerals are brown to green to black an
41、d generallyoccur as prismatic units. Olivine is usually olive green, glassyin appearance, and usually altered. Biotite has excellent cleav-age and can be easily cleaved into thin flakes and plates. Theseminerals can be found as components of a variety of rocks, andin sands and gravels. Olivine is fo
42、und only in dark igneousrocks where quartz is not present, and in sands and gravelsclose to the olivine source.8. Micaceous Minerals8.1 Micaceous minerals have perfect cleavage in one direc-tion and can be easily split into thin flakes. The mica mineralsof the muscovite group are colorless to light
43、green; of thebiotite group, dark brown to black or dark green; of thelepidolite group, white to pink and red or yellow; and of thechlorite group, shades of green. Another mica, phlogopite, issimilar to biotite, commonly has a pearl-like luster and bronzecolor, and less commonly is brownish red, gree
44、n, or yellow.The mica minerals are common and occur in igneous, sedi-mentary, and metamorphic rocks, and are common as minor totrace components in many sands and gravels. The muscovite,biotite, lepidolite, and phlogopite minerals cleave into flakesand plates that are elastic; the chlorite minerals,
45、by comparison,form inelastic flakes and plates. Vermiculite (a mica-likemineral) forms by the alteration of other micas and is brownand has a bronze luster.8.2 Because micaceous materials have a high surface area,they can influence the properties of freshly mixed and hardenedconcrete. Aggregates wit
46、h a high mica content can reduceworkability and increase the water demand of the concrete(15). The shape and perfect cleavage of micaceous mineralsmay result in a poor bond to the cementitious paste (16).9. Clay Minerals9.1 The term “clay” refers to natural material composed ofparticles in a specifi
47、c size range less than 2 m (0.002 mm).Mineralogically, clay refers to a group of layered silicateminerals including the clay-micas (illites), the kaolin group,very finely divided chlorites, and the swelling clayssmectiteincluding montmorillonites. Members of several groups, par-ticularly micas, chlo
48、rites, and vermiculites, occur both in theclay-size range and in larger sizes. Some clays are made up ofalternating layers of two or more clay groups. Random, regular,or both types of interlayering are known. If smectite is asignificant constituent in such mixtures, then fairly largevolume changes m
49、ay occur with wetting and drying.9.2 Clay minerals are hydrous aluminum, magnesium, andiron silicates that may contain calcium, magnesium, potassium,sodium, and other exchangeable cations. They are formed byalteration and weathering of other silicates and volcanic glass.The clay minerals are major constituents of clays and shales.They are found disseminated in carbonate rocks as seams andpockets and in altered and weathered igneous and metamorphicrocks. Clays may also be found as matrix, void fillings, andcementing material in sandstones and other sedimentary rocks.9.3 Most
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