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- A -

AAR - See Alkali-Aggregate Reaction.

AASHTO - The American Association of State Highway and Transportation Officials.

ACR - See Alkali-Carbonate Reaction.

Actinolite - One of the amphibole group of minerals. A light green silicate of calcium, magnesium, and iron.

Alkali - For purposes of evaluating ASR potential, term commonly refers to sodium and potassium occurring in constituents of concrete and mortar. Usually expressed in chemical analysis as the oxides Na2O and K20. Actually these are indirect measurement of free hydroxyl ion which is associated with sodium and potassium.

Alkali-Aggregate Reaction - Chemical reaction in either mortar or concrete between alkalis ( hydroxyl ions associated with sodium and potassium ) from portland cement and other constituents, such as admixtures and pozzolans, and certain constituents of some aggregates. Under certain conditions, this reaction can result in deleterious expansion of the mortar or concrete resulting in cracking.

Alkali-Carbonate Reaction - Chemical reaction in either mortar or concrete between alkalis ( hydroxyl ions associated with sodium and potassium ) from portland cement and other constituents, such as admixtures and pozzolans, and certain carbonate rocks, particularly certain calcitic dolomite and dolomitic limestones, present as components of some aggregates. The reaction and products of the reaction may cause abnormal expansion and cracking of concrete in service.

Alkali-Silica Reaction - Chemical reaction in either mortar or concrete between alkalis ( hydroxyl ions associated with sodium and potassium ) from portland cement and other constituents, such as admixtures and pozzolans, and certain siliceous rocks or minerals, such as opaline chert, strained quartz, and certain volcanic glasses, present as constituents of some aggregates. The product of the reaction, a silica gel, can cause expansion and cracking of the concrete or mortar.

Amphibole - A group of silicate minerals having a characteristic crystal form and cleavage. Can be considered as metasilicates, but of complex composition.

Amphibolite - A metamorphic rock consisting chiefly of hornblende, or of at least one member of the amphibole group of minerals. It is , as a rule, a synonym of hornblende schists, but is preferable to the latter when a highly foliated structure is not found.

Andesite - A fine-grained igneous rock composed of plagioclase feldspar and biotite, hornblende, or augite. Sometimes porphyritic, that is having large, distinct crystals in a fine-grained groundmass. Included in the group of rocks collectively called felsite.

Anisotropic - In optical mineralogy and petrography, the ability of a material to doubly refract light. Characteristic of all non opaque crystalline substances except those belonging to the isometric system, which are called isotropic.

Aplite (Aplitic Granite) - A fine-grained granite consisting chiefly of granite and feldspar.

Argillaceous - Containing an appreciable amount of clay.

Argillite - An argillaceous rock, differing from shale in being hardened, and from slate in having no slaty cleavage.

Arkosic - Having the properties of arkose, which may be either a sandstone containing a large percentage of feldspar or a sedimentary rock formed from material derived from the disintegration of granite, with the grains of rock transported and redeposited with little sorting.

ASR - See Alkali-Silica Reaction.

ASTM - American Society for Testing Materials.

Augen - The German word for eyes used as a prefix before certain rock species, especially gneiss, to describe large minerals or groups of minerals that contrast with the rest of the rock.

Augite - A variety of the mineral pyroxene containing aluminum. Usually black or dark green, occurring in igneous rock such as basalt. Sometimes used to refer to any pyroxene.

- B -

Basalt - A dark grained to black, dense to fine-grained igneous rock, consisting of plagioclase feldspar (usually labradorite), augite, olivine, and usually magnetite. Some glass may be present. This is one of the type of rock which are referred to by the word "trap."

Basic - A descriptive term for igneous rocks containing less than about 52 percent silica (SiO₂).

Becke line - A line of high-intensity light formed around a translucent ( or transparent ) particle mounted, for example, in a refractive-index liquid on a glass microscope slide, and illuminated from below. The line of light is caused by concentration by split reflection or refraction.

Biotite - A species of mica, generally black or dark green, forming a common constituent of crystalline rocks.

BRE - Building Research Establishment, United Kingdom.

Breccia - A rock composed of angular fragments of other rock cemented together.

- C -

Calcareous - Containing calcite, calcium carbonate, or limestone.

Calcite - A mineral having the composition calcium carbonate ( CaCO3 ) and a specific crystal structure. This mineral is the principal constituent of limestone, chalk and marble. Used as a major constituent in the manufacture of portland cement.

Carbonaceous - Containing carbon.

Carbonation - Reaction between carbon dioxide from air and a hydroxide to form a carbonate, especially in cement paste, mortar, or concrete. The reaction with calcium hydroxide in these materials produces calcium carbonate, thus reducing the pH of the system. Progressive cerbonation of concrete can result in increased corrosion of rebar and reinforcing elements.

Cement, low-alkali - A portland cement that contains a relatively small amount of alkali expressed as sodium and / or potassium content. In North America the definition of low-alkali varies between 0.6 and 0.4 % of Na2O equivalent . The formula for calculating Na2O equivalent is :
      Na2O % = Na2O % + ( 0.658 X K2O % )

Chalcedony - A transparent or translucent and finely crystalline variety of quartz.

Chert - A very fine grained siliceous rock characterized by hardness and conchoidal fracture in dense varieties. The fracture becomes splintery and the hardness decreases in porous varieties. Characteristically shows a variety of colors. Composed of silica in the form of chalcedony, cryptocrystalline or microcrystalline quartz, or opal, or any combinations of these.

Chlorite - Any of a group of hydrated silicates containing aluminum and iron. Green in color. Derived from augite, hornblende, or biotite. Resembles mica in appearance but the flakes are not as elastic.

Conglomerate - A rock composed of rounded fragments of another rock cemented together into a coherent mass.

- D -

Dacite - A fine-grained, igneous rock composed essentially of plagioclase feldspar and quartz, with or without hornblende and biotite. Included in the group of rocks collectively named felsite.

Diabase - A basic igneous rock mineralogically the same as basalt and gabbro, but coarser-grained than basalt and finer-grained than gabbro. The plagioclase forms lath-shaped crystals lying in all directions among irregular grains of augite, giving rise to a peculiar diabasic texture. Included in the general name of "trap."

Diorite - A coarse to medium grained igneous rock composed essentially of plagioclase feldspar with some ferromagnesium minerals such as hornblende, augite, and biotite. The coarser grained equivalent of andesite.

Dolomite - A limestone or marble containing a large amount of magnesium carbonate. Also a rock having approximately the same composition as dolomite : 45 % magnesium carbonate and 55 % calcium carbonate.

DOT - Department of Transportation.

- E -

Eclogite - A foliated metamorphic rock consisting of bright green pyroxene, actinolite, red garnet, and minor minerals.

Epidosite - A metamorphic rock resembling schist but composed essentially of epidote.

Epidote - A silicate of calcium, aluminum, and iron. Of yellowish-green color. The presence of epidote in rock indicates the advance of alteration.

ETG - Expert Task Group. A common term used by FHWA and DOT's to signify a group of experts assigned to perform a particular technical task for a defined period of time.

Ettringite - A naturally occurring mineral characterized as a high sulfate calcium sulfoaluminate ( 3 CaO . Al3O3 . 3 CaSO4 . 30-32 H2O ). It is formed as a cement hydration product or by sulfate attack in mortar and concrete. It is also the product of the principal expansion-producing reaction in expansive cements. Was designated as "cement bacillus" in older literature.

- F -

Feldspar - A general name for a group of important rock-forming minerals which are potassium-aluminum silicates and plagioclase, a subgroup composed of sodium-aluminum silicate or calcium-aluminum silicates or mixtures of these. Includes orthoclase and microcline.

Feldspathic - Containing feldspar.

Felsite - A general term for dense, igneous rock composed of quartz, feldspar, and ferromagnesium minerals which are so fine grained that the composition of the rock is difficult to determine. The group includes rhyolite, dacite, trachyte, and andesite.

Ferruginous - Containing iron.

FHWA - Federal Highway Administration, branch of the US Department of Transportation.

Flint - A dense, black to dark gray variety of chert.

Fly Ash - The finely divided residue resulting from the combustion of ground or powdered coal which is transported from the firebox through the boiler by the flue gases. The composition of this ash varies according to the coal used and is usually pozzolanic in nature.

Fluorescence - The emission of visible light by a substance which is exposed to ultraviolet light.

Fluorescence Microscopy - A branch of microscopy whereby ultraviolet or near ultraviolet light is used to produce fluorescence to facilitate microscopic observations and aid in identification of substances which naturally exhibit the property to fluoresce.

Fossiliferous - Containing fossils.

- G -

Gabbro - A coarsely crystalline igneous rock composed mainly of limesoda feldspar, pyroxene, amphibole, and frequently olivine. Accessory minerals are magnetite or ilmenite or both and apatite. Generally dark colored. Ferromagnesium minerals are generally more abundant than feldspar. A coarse grained equivalent of basalt.

Gel - In alkali-silica reaction, the clear to gelatinous reaction product of silica with alkalis. This gel has a variable composition containing SiO2, CaO, and alkalis ( sodium and potassium ). A range of compositions is characterized by having high absorptivity for water causing the gel to swell thus causing the typical cracking observed in deleterious ASR.

GGBFS - See Ground Granulated Blast Furnace Slag.

Gneiss - A coarsely laminated or foliated metamorphic rock corresponding in composition to granite or other coarse grained igneous rocks containing feldspar.

Gneissoid - Tending to have the same structure as gneiss.

Granite - A granular igneous rock composed essentially of quartz, feldspar, and mica. The feldspar is generally the variety containing potassium (orthoclase and microcline) but some limesoda feldspar may be present. Hornblende, apatite, zircon, and magnetite are usually present in minor amounts.

Granodiorite - A name used for rocks intermediate between granite and quartz-diorite.

Granulite - A moderately fine grained metamorphic rock composed chiefly of quartz and feldspar, but commonly containing some garnet.

Graphic Granite - A variety of granite in which the quartz is disposed in the feldspar such that in a cross section it has some resemblance to written Hebrew and cuneiform writing.

Greenstone - An old field name for compact, igneous rocks which have developed enough chlorite in alteration to give them a greenish color. If the rock is finely foliated, it is called greenstone schist.

Ground Granulated Blast Furnace Slag - The glassy, granular material formed when molten blast-furnace slag is rapidly chilled, as by immersion in water. The material is pozzolanic in nature and generally ground to fine particle size for use as a mineral admixture in concrete.

Gypsum - Hydrated calcium sulfate.

- H -

Hematite - Iron oxide.

Hornblende - The most common variety of the amphibole group of minerals. A silicate containing iron and magnesium of complex composition.

Hornblendite - A coarse grained igneous rock composed solely or predominantly of hornblende.

Hypersthene - One of the pyroxene group of minerals. A silicate of iron and magnesium.

- I -

Igneous Rocks - A group of rocks formed by solidification from a molten state. Rocks which were cooled quickly are termed volcanic or extrusive, those which were cooled slowly are described as plutonic or intrusive.

Immersion Mount - See Powder Mount.

Indurated - Hardened. Applied to rocks hardened by heat, pressure, or the addition of some other mineral.

Isotropic - In optical mineralogy, those minerals that only singly refract transmitted light. The property of a substance to transmit light with equal velocity in all crystallographic directions. Opposite of anisotropic.

ISTEA - Intermodal Surface Transportation Efficiency Act. Funded by the US Congress in 1991 and expired in Fall of 1997.

- J -

- K -

- L -

Leucite - A silicate of potassium and aluminum.

Limestone - The general name for sedimentary rocks composed essentially of calcium carbonate.

Lithium - An element of the alkali metal group that is the lightest metal known and never found uncombined in nature. It is not considered an alkali in cement and concrete terminology. Has been shown to control ASR when added to mortar and concrete as a salt.

- M -

Map cracking - 1) Intersecting cracks that extend below the surface of hardened concrete. Caused by shrinkage of the drying surface of concrete which is restrained by concrete at greater depths where either little or no shrinkage occurs. Cracks vary in width from fine and barely visible to open and well-defined. 2) The most obvious symptom of alkali aggregate reaction between alkalies in the mix and mineral constituents in aggregate within hardened concrete. Cracking is due to a differential rate of volume change in different portions of the concrete. Cracking is usually random and can be on a fairly large scale. In severe cases the width of cracks may reach 0.50 inches or more.

Marble - A metamorphosed and recrystallized limestone. Also commonly in the trade the term refers to any limestone which will take a polish.

Marl - A calcareous clay, or mixture of clay and particles of calcite or dolomite. Usually fragments of shells.

Metamorphic rock - A rock which has been altered by heat or intense pressure, causing new minerals and structures to be formed.

Mica - Any of a group of silicate minerals which crystallize to form a material which can be separated in very thin more or less elastic flakes. The principal micas are biotite or black mica and muscovite, a more or less colorless, translucent variety.

Microgranite - A name used for finely grained granite. Synonymous to aplite.

Microcline - One of the so-called "alkali" or "potassium" feldspars. A silicate of potassium and aluminum.

Mohs Scale - Arbitrary ( quantitative ) units, ranging from 1 to 10, by means of which the scratch hardness of a mineral is determined. Each unit of hardness is represented by a mineral that can scratch any other mineral having a lower-ranking number. The minerals are ranked from talc or 1 ( the softest ), upward through gypsum or 2, calcite or 3, fluorite or 4, apatite or 5, orthoclase or 6, quartz or 7, topaz or 8, corundum or 9, and diamond or 10 (the hardest ).

MSDS - Material Safety Data Sheet.

Muscovite - A light-colored, translucent mica.

- N -

Natural pozzolan - Either a raw or calcined natural material that has pozzolanic properties. Examples are volcanic rock or pumice, opaline chert and shales, tuffs, and some diatomaceous earths.

Nephelite (Nepheline) - A silicate of sodium, potassium, and aluminum occurring in igneous rocks.

Nodular - Having the shape of, or composed of, small, roundish lumps.

Novaculite - An excessively fine grained rock composed essentially of quartz. Claimed to be a consolidated siliceous slime of sedimentary origin.

NRC - Nuclear Regulatory Commission, United States of America.

- O -

Obsidian - Volcanic glass.

Olivine - A silicate of iron and magnesium.

Oolite - A variety of limestone consisting of round grains like the roe of a fish.

Oolitic - Composed of or similar to oolite.

Opal - A mineral composed of amorphous hydrous silica ( SiO2.H2O ).

Opaline - Containing opal.

Orthoclase - One of the so-called "alkali" or "potassium" feldspars. A silicate of potassium and aluminum.

- P -

Pegmatite - Giant granite. An igneous rock, usually irregular in texture and composition. Composed mainly of silicate minerals of large size.

Peridotite - A granular igneous rock composed essentially of olivine with some form of pyroxene or hornblende. Biotite and chromite are the chief accessory minerals.

Petrography - The branch of petrology dealing with the description and systematic classification of rocks aside from their geologic relations. Classification is achieved mainly by chemical and microscopical laboratory testing. Term is also used loosely for petrology.

Petrology - The science of rocks and minerals. Science deals with their origin, structure, composition and all descriptive visual and geologic observations and classifications.

Pisolitic - Consisting of rounded grains like peas or beans.

Plagioclase - A general name for the sodalime feldspars which vary in composition from a silicate of sodium and aluminum to a silicate of calcium and aluminum. Term includes all mixtures of these types.

Polarized-Light Microscope - A microscope set-up to view specimens using plane-polarized light, i.e. light that vibrates in only one plane. Used to distinguish and characterize rocks and minerals.

Pore Solution - Water-based liquid that remains entrained in concrete and mortar paste and contains water soluble ionic species. This solution can be extracted from the concrete matrix by literally "squeezing" the solution out by means of high pressures.

Porphyry - Any igneous rock in which large conspicuous crystals are enclosed by a fine grained groundmass.

Powder Mount - Particles embedded or immersed in a liquid ( or other material such as hardened epoxy resin ) on a glass microscope slide. To hold the sample in place and visualize under a microscope, a thin cover glass is placed on top of the particles. Also referred to as Immersion Mount.

Pozzolan - A siliceous or siliceous and aluminous material which by itself possesses little or no cementitious value but that will, in finely divided form and in the presence of moisture, chemically react with calcium hydroxide at ambient temperatures to form compounds which exhibit cementitious properties. Pozzolans can be man-made such as fly ash, or naturally occurring.

Pumice - A very porous volcanic glass, possibly best described as glass froth.

Pyroxene - A group of silicate minerals, of simple or complex composition, which have essentially the same crystal form and many similar physical properties. Chiefly silicates of iron, calcium, and magnesium.

Pyroxenite - A coarse grained igneous rock with pyroxene as the only or predominant mineral.

- Q -

Quartz - Silicon dioxide, in hexagonal crystals or crystalline masses.

Quartzite - A metamorphosed quartz sandstone formed by the deposition of secondary silica between the original grains so that the rock is more firmly cemented and less porous than the original sandstone.

- R -

Reactive Aggregate - Aggregate containing components containing forms of silica capable of reacting chemically with the alkalies and hydroxyl ion in the pore solution of portland cement concrete or mortar under ordinary conditions of exposure to form alkali-silica gels. This reaction can result in harmful expansion, cracking, and / or staining.

Refraction - A change of direction of a ray of light ( or other radiation ) when it passes from one medium to another of different optical density.

Refractive Index - The ratio of the speed of visible light in air to that in a substance. Each substance has a particular refractive index that is unique to that substance, so measurement of the refractive index is used to assist in the identification of a substance.

Rhyolite - A fine grained igneous rock composed essentially of orthoclase feldspar and quartz, or of rock glass having the same composition, with or without biotite, hornblende, or pyroxene. The fine grained equivalent of granite.

- S -

Sandstone - A sedimentary rock consisting of grains of sand, usually quartz, cemented by some substance such as silica, iron oxide, calcite, etc.

Schist - A crystalline metamorphic rock that can readily be split or cleaved due to its foliated or parallel structure developed by shearing and recrystallization under pressure.

Schistose - Having a structure similar to schist.

Sedimentary Rocks - Rocks formed as the result of accumulation of sediment in water or air. The sediment can be particular, as in sand grains or clay, or a chemical or biochemical precipitate as in diatomaceous earth.

Sericite - A minutely crystalline variety of muscovite. Light-colored mica.

Serpentine - A mineral composed of hydrous magnesium silicate and formed by an alteration of silicates rich in magnesium such as pyroxene, amphibole, and especially olivine. The name is also used for rock composed of the mineral and altered from peridotite or pyroxenite.

Shale - A fine grained rock formed by the consolidation of clay or mud. Does not have a finely stratified or laminated structure.

SHRP - Strategic Highway Research Program. Established by the US Congress in 1987 as a five-year, US $ 150 million research program to improve the performance and durability of US highways and to make them safe for motorists and highway workers.

Silica Fume - Extremely fine noncrystalline silica produced by electric arc furnaces as a byproduct of the production of metallic silicon or ferrosilicon alloys. Used as a concrete mineral admixture. Also available as a condensed silica fume.

Siliceous - Containing silica, especially quartz.

Sinter - A chemical sediment deposited by a mineral spring.

Slate - A dense, extremely fine grained metamorphic rock produced by compression of clays, shales, etc. Has an excellent parallel cleavage so that it breaks into thin plates or pencil like shapes.

Soapstone - A soft, massive metamorphic rock composed of a variable mixture of talc and chlorite.

Steatite - Other name for soapstone.

Syenite - A granular, igneous rock composed of orthoclase with or without microcline, plagioclase, hornblende, biotite, and augite. May be considered a granite without quartz.

- T -

Talc - Hydrous magnesium silicate. A soft mineral with a soapy feel.

Tephrite - A very fine grained rock composed of plagioclase feldspar, nephelite, and augite but with little or no olivine. May resemble a porphyry.

Thin Section - A thin translucent slice of a substance mounted on a glass microscope beneath a cover slip. The substance can be a rock, mineral, bone, concrete, etc.

Topaz - A hard mineral composed of aluminum fluosilicate. Also a semi-precious stone.

Trachy-Andesite - A rock intermediate between trachytes and andesite.

Trachyte - A fine grained igneous rock consisting mainly of feldspars containing potassium, usually with mica, amphibole, and pyroxene but with little if any quartz. Sometimes glassy in nature. The fine grained equivalent of syenite.

Trap - A common name for dark, fine grained igneous rock, especially basalt and diabase.

Travertine - A rock composed of calcium carbonate deposited from solution in ground or surface waters.

TRB - Transportation Research Board, United States of America.

Tuff - A sedimentary rock composed of fine material explosively ejected from a volcano and subsequently compacted to a solid mass.

TWG - Technical Working Group.

- U -

Ultraviolet Light - Radiation beyond the visible spectrum in the violet end of the spectrum. Wavelengths in this spectrum are shorter than those of visible light and longer than those of X-Rays.

Unakite - A granite containing pink feldspar and rich in green epidote.

Uralite - A variety of hornblende in the form of fibers or fine needles.

Uralitic - Containing uralite.

Uranyl Acetate Solution - UO2(C2H3O2)2 * H2O A solution containing uranium acetate that is applied to concrete to detect possible alkali-silica gel reaction products. Used in AASHTO T 299 testing procedure.

- V -

Vitrified - Converted into a glassy substance by heat and fusion.

Vitreous - Like glass.

Volcanic - A variety of igneous rock which is fine grained or glassy due to rapid cooling upon or near the surface of the earth.

- W -

- X -

X-Ray Diffraction - A characteristic reflection and refraction of X-Rays by substances having a regular arrangement of atoms. The phenomenon is used to identify substances having such a structure during petrographic examination.

X-Ray Fluorescence - Characteristic secondary radiation emitted by an element or substance as a result of excitation by X-Rays. Phenomenon is used in chemical analysis of a sample.

- Y -

- Z -