Construction Terms & Definitions
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A Aluminum & Rescreening offers this page as a resource to our visitors to become more familiar with common constrction terms.
abrasion damage - surface deterioration caused by rubbing and friction against the surface.
abrasive - any hard, strong substance, such as rocks, sand, water, or minerals, that will cut, scour, pit, erode, or polish another substance.
abrasive blasting - a process for roughening, cleaning, or finishing a surface by propelling an abrasive medium at high velocity against it; commonly used methods include sandblasting, shotblasting, and high-pressure water blasting.
accelerated aging - deteriorating a material at a faster-than-normal rate by subjecting the material to specified accelerated test conditions.
accelerator - (1) a substance which, when added to a cementitious material, increases the rate of hydration of the hydraulic cement, shortens the time of setting, or increases the rate of hardening, strength devlopment, or both; (2) any substance which increases the rate of a chemical reaction.
acceptance test - a test conducted to determine whether an individual lot of materials conforms to specifications or to determine the degree of uniformity of the material, or both.
acid etching - application of acid to clean or alter a concrete surface; typically used only when noalternative means of surface preparation can be used.
acoustic emission - sounds, both audible and subaudible, that are generated when a material undergoes irreversible changes, such as cracking in concrete; provides the basis for a nondestructive monitoring technique.
acoustic impact - a method used to detect the presence of delaminations or subsurface voids in concrete based on the sounds made by the concrete upon impact. (See also chain drag and sounding.)
acrylic resin - one of a group of thermoplastic resins formed by polymerization of the esters or amides in acrylic d; used in concrete maintenance and repair as a surface sealer or bonding agent.
activator - a material that actuates a catalyst.
active cracks - those cracks for which the mechanism causing the cracking is still at work; any crack that is still moving.
adhesion - the bonding of two surfaces through interfal effects such as molecular (valence) forces or interlocking action, or both.
adhesive failure - a rupture of an adhesive bond such that the separation appears to be between the adhesive and one or both of the adherends. (See also cohesive failure.)
adhesives - the group of materials used to cause similar or dissimilar materials to cohere.
admixture - a material other than water, aggregates, hydraulic cement, or fiber reinforcement, added to concrete, mortar, or grout, during batching or mixing to enhance plastic or hardened material properties, or both.
advancing-slope grouting - a grout injection technique that causes the leading edge of a mass of grout to move horizontally through preplaced aggregate.
age hardening - the progressive change in the chemical and physical properties of an adhesive leading to embrittlement. (see also aging.)
aggregate - granular materials, such as sand, gravel, and crushed stone, commonly used in concrete, mortar, or grout.
aggregate, reactive - aggregate containing substances capable of reacting with the alkalies in portland cement; products of the reaction may cause abnormal expansion and cracking of concrete or mortar under certain service conditions.
aging - the cumulative effects of time on the properties of materials or substances.
agitation - the mixing and homogenization of slurries or finely ground powders by either mechanical means or injection of air.
agitator - a device for maintaining plasticity and preventing segregation of mixed grout, mortar, or concrete by shaking or stirring.
agitator tank - a vertical, open-top tank equipped with rotation blades used to prevent segregation of mixed grout.
air-entraining admixture - a material that creates microscopic air bubbles in concrete, mortar, or cement paste during mixing; used to increase the workability and frost resistance of the mixture.
air content - the volume of air voids in cement paste, mortar, or concrete, exclusive of pore space in aggregate particles, usually expressed as a percentage of total volume of the paste, mortar, or concrete.
air entrainment - the deliberate addition of microscopic air bubbles (generally smaller than 1 mm) to concrete or mortar during the mixing. (See also air-entraining admixture.)
air ring - perforated manifold in nozzle of wet-mix shotcrete equipment through which high pressure air is introduced into the material flow.
air-water jet - a high-velocity jet of air and water mixed at the nozzle, used to clean surfaces or remove deteriorated concrete; water sprayed at pressures less than 5,000 psi (35 MPa) will remove dirt and loose, friable material; water sprayed at pressures between 5,000 and 45,000 psi (35 - 300 MPa) will remove heavy encrustations of dirt and loose, friable material, including deteriorated concrete.
alignment wire - see ground wire.
alkali - salts of alkali metals, specifically sodium and potassium, occurring in constituents of concrete and mortar; usually expressed in chemical analyses as the oxides Na20 and K20.
alkali-aggregate reaction - a chemical reaction between alkalies (sodium and potassium) from portland cement or other sources and certain constituents of some aggregates that can cause abnormal expansion and cracking of concrete or mortar under certain service conditions.
alkali-carbonate rock reaction - the reaction between the alkalies (sodium and potassium) in portland cement and certain carbonate rocks (particularly calcitic dolomite and dolomitic limestones) present in some aggregates.
alkali-silica reaction - the reaction between the alkalies (sodium and potassium) in portland cement and certain siliceous rocks or minerals, such as opaline chert, strained quartz, and acidic volcanic glass, present in some aggregates.
alligator cracks - surface cracking that forms a pattern similar to alligator hide.
ambient - surrounding natural conditions or environment in a given place and time.
angle of repose - the angle between the horizontal and the natural slope of loose material below which the material will not slide.
anisotropic - exhibiting different physical properties in different directions.
anode - the electrode in electrolysis at which negative ions are discharged, positive ions are formed, or other oxidizing reactions occur.
anodes, sacrificial - see sacrificial anodes.
anodic inhibitor - an inhibitor that reduces the corrosion rate by acting on the anodic (oxidation)reaction.
anodic protection - a technique to reduce the corrosion rate of a metal by polarizing it into its passive region where dissolution rates are low.
anodic reaction - corrosion reaction in which electrons are consumed; also referred to as oxidation.
anodic ring effect - corrosion process in which the steel reinforcement in concrete surrounding a repair area begins to corrode preferentially to reinforcement in the newly repaired area.
anticoagulant - a substance which prevents the coagulation of a colloid suspension or emulsion; also called a stabilizer and latex preservative.
antifoaming agent - an additive used to increase surface tension and reduce foaming tendencies,particularly in admixtures and materials applied by roller coating equipment.
antiwashout admixture - an admixture that increases the cohesiveness of concrete and prevents an excessive amount of fines from washing away from the aggregates when the concrete comes in contact with water.
application life - the period of time during which a material, after being mixed with a catalyst or exposed to the atmosphere, remains suitable for application.
application rate - the quantity (mass, volume, or thickness) of material applied per unit area.
aramid - a manufactured fiber in which the fiber-forming substance is a long-chain synthetic aromatic polyamide in which is at least 85 percent amide linkages are attached directly to two aromatic rings. 4
articulated joint - a joint with movement limited by restraint.
aspect ratio - the ratio of length to diameter of a fiber.
autogenous healing - a natural process of filling and sealing cracks in concrete or mortar when kept damp.
backer rod - a flexible, compressible rod placed in a joint to reduce the depth of sealant and improve its shape factor; it also serves to support the sealant against sagging and indentation.
backpack grouting - filling the annular space between a permanent tunnel lining and the surrounding formation with grout.
base - primary material in a multi-component system.
batch - quantity of material (concrete, mortar, grout, etc.) mixed at one time.
batch method - a quantity of grout materials are mixed or catalyzed at one time prior to injection.
batch mixer - a machine that mixes batches of concrete, mortar, or grout, in contrast to a continuous mixer.
batching - weighing or volumetrically measuring and introducing into the mixer the ingredients for a batch of either concrete or mortar.
bead - a strip of applied sealant, glazing compound, or putty.
bed joint - a horizontal mortar joint between a repair material and a substrate.
bentonite - a distinct type of fine-grained clay containing not less than 85 percent montmorillionite clay.
binders - cementing materials, either hydrated cements or products of cement or lime and reactivesiliceous materials or other materials such as polymers that form the matrix of concretes, mortars, and sanded grouts.
blanket grouting - a method for reducing the permeability and strengthening the upper layers of bedrock by drilling and grouting shallow, closely spaced shallow holes according to a grid pattern.
bleaching - the fading of color toward white generally caused by exposure to chemicals or ultraviolet radiation.
bleeding - (1) the flow of mixing water within, or its emergence from newly placed concrete or mortar; (2) the absorption of oil resin or plasticizer from a compound into an adjacent porous surface; (3) the diffusion of color matter through a coating from underlying surfaces causing a color change.
blemish - a shallow defect in a hardened material that mars an otherwise smooth, uniformly colored surface. (See also bleaching, bloom, bug holes, efflorescence, honeycomb, laitance, mottled, popout, rock pocket, and sand streak.)
blended cement - see cement, blended.
blistering - (1) the irregular raising of a thin layer at the surface of placed mortar or concrete during or soon after completion of the finishing operation; (2) bulging of the finish plaster coat as it separates and draws away from the base coat; (3) the formation of air or gas pockets trapped within a thin-film coating, elastomeric membrane, or any impervious membrane.
bloom - (1) a visible exudate of efflorescence on the surface of a material; (2) a haziness which develops on coated surfaces caused by the exudation of a component of the coating system.
blow pipe - air jet used in shotcrete gunning to remove rebound other loose material from the work area.
blushing - a coating defect which manifests itself as a milky appearance which is generally caused by rapid solvent evaporation or the presence of excessive moisture during the curing process.
board butt joint - shotcrete construction joint formed by sloping gunned surface to a 1-in. (25-mm) board laid flat.
bond - adhesion and grip of a material to other surfaces against which it is placed; adherence between repairs and existing substrates.
bonded anchors - anchor systems which develop their holding capacities by the bonding of the cementitious or polymer adhesive to both the anchor and the concrete at the wall of the drilled hole.
bond breaker - a material used to prevent adhesion at a designated interface.
bond line - the interface between two surfaces bonded together with an adhesive.
bond strength - resistance to separation of a repair from the existing substrate or from reinforcing and other materials with which it is in contact.
bond strength, direct tension - see tensile bond strength.
bond strength, shear - see shear-bond strength.
bond strength, slant shear - see slant-shear bond strength.
bonding agent - a material applied to a suitable substrate to enhance bond between it and a succeeding layer.
boom-mounted breakers - mechanically operated equipment for removal of concrete by repeated, highenergy and low-frequency striking of the surface to spall and fracture the concrete. (See also hand-held breakers, impact breakers, and scabblers.)
brittle - a tendency to crack or break when subjected to deformation; frangible.
broadcast - to toss granular material, such as sand, over a horizontal surface so that a thin, uniform layer is obtained. 6
broom and seed - a method for application of polymer concrete in which alternate layers of resin and aggregate are built up to form an overlay.
bruised surface - a surface layer weakened by interconnected microcracks in concrete substrates caused by use of high-impact, mechanical methods for surface preparation; fractured layer typically extends to a depth of 1/8 to 3/8 in. (3 to 10 mm) and frequently results in lower bond strengths as compared to surfaces prepared with nonimpact methods.
bubbling - a temporary or permanent film defect in which bubbles of air or solvent vapor are present in the applied film.
bug holes - small cavities in the surface of formed concrete caused by entrapment of air bubbles during placement and consolidation; usually no larger than 5/8 in. (15 mm) in diameter.
build - the wet or dry thickness of a coating or film.
build-up - placing material in layers to increase thickness.
bush-hammer - a serrated hammer with rows of pyramidal points used to roughen or dress a surface; to finish a surface with a bush-hammer.
calcium chloride - a white, deliquescent, hygroscopic compound, CaCl2; can be used, in various technical grades, as a drying agent, an accelerator, a deicing chemical, a refrigerant, and to prevent dust.
carbon fiber - reinforcing fiber with light-weight, high-strength, and high-stiffness characteristicsproduced by oxidizing organic polymer fibers.
carbonation - the conversion of calcium ions in hardened cementitious materials to calcium carbonate by reaction with atmospheric carbon dioxide.
cast-in-place - frequently used repair technique in which mortar, concrete, or other materials are deposited in workable condition in the place where they harden and become part of the structure.
catalyst - a substance that significantly increases the rate of curing of a binder when added in a small quantity relative to the amount of primary reactants.
catalyst system - those materials that, in combination, cause chemical reactions to begin; catalystsystems normally consist of an initiator (catalyst) and an activator.
cathode - the electrode at which chemical reduction occurs.
cathodic protection - a form of corrosion protection for reinforced concrete wherein a sacrificial metal is caused to corrode in preference to the reinforcement, thereby protecting the reinforcement from corrosion.
cathodic protection, impressed current - a protection system that uses an external power supply to force a small amount of electric current through the reinforcing steel to counteract the flow of current caused by the corrosion process; a metal, such as platinum that corrodes at a very slow rate, is typically provided as an anode.
cathodic protection, sacrificial - protection system that does not require an external power supply; a metal, such as zinc that is less noble or more prone to corrosion than steel, corrodes in place of the reinforcing steel thus protecting the structure.
caulk - to install or apply a sealant across or into joints, cracks, or crevices to prevent the passage of air or water.
cavitation damage - pitting of concrete caused by implosion of water vapor bubbles in fast-flowing water; bubbles form in areas of subatmospheric pressures immediately downstream from an obstruction or offset and collapse as they enter areas of higher pressure.
cement, expansive - a type of cement that produces a paste that, after setting, increases in volume to a significantly greater degree than does portland-cement paste; used in some repair materials to compensate for drying shrinkage.
cement, high-early-strength - cement that reaches a given level of strength in mortar or concrete earlier than normal cement does.
cement, portland - a hydraulic cement produced by pulverizing portland-cement clinker and usually containing calcium sulfate.
cement, regulated set - a hydraulic cement containing fluorine-substituted calcium aluminate, capable of very rapid setting.
cement, sulfate-resistant - portland cement with a low tricalcium aluminate content, which makesconcrete more resistant to damage from dissolved sulfates in water or soils.
cement, white - portland cement which hydrates to a white paste, made from raw materials of low iron content.
cement paste - a mixture of cement and water.
cementation process - pressure injection of cement grout into gravel, fractured rock, etc, to solidify it.
cementitious - having cementing properties.
chain drag - a nondestructive testing method in which the sounds from chains dragged over a concrete surface are used to detect delaminations; dull or hollow sounds indicate delaminated areas, whereas nondelaminated concrete exhibits a clear ringing sound.
chalking - the loose powder caused by decomposition of a concrete surface or degradation of a coating.
charging - placing materials into a mixer or other container for further processing.
checking - shallow, closely spaced cracks that form an irregular pattern. (See also craze cracks and
chemical attack - material degradation as a result of the action of chemical agents such as ds, bases, salts, and moisture.
chemical bond - bond between materials that is the result of cohesion and adhesion developed by chemical reaction.
chemical compatibility - any combination of materials that results in a chemically stable repair system.
chemical grout - any grouting material characterized by being a true solution; no particles in suspension. (See also particulate grout.)
chemical grout system - any mixture of materials used for grouting purposes in which all elements of the system are true solutions (no particles in suspension).
chemical resistance - resistance to chemical reaction as a result of contact with or immersion in various solvents, ds, alkalies, salts, etc.
chipping - to remove all or part of a hardened concrete section with a chisel.
chisel point - point with two major planes forming a ÒVÓ and a pair of minor planes on each flank; forming a hexagonal cross section.
chloride content - total amount of chloride ion present in concrete or mortar.
chloride diffusion - the dispersal of chlorides within a concrete section.
chloride ion - anion of the commonly used deicing salts and of the accelerating admixtures calcium chloride and sodium chloride.
chloride threshold - the amount of chloride required to initiate steel corrosion in reinforced concrete under a given set of exposure conditions; commonly expressed in percent of chloride ion by mass of cement.
chlorinated rubber - resin produced by the reaction of natural rubber with chlorine gas; coatingsformulated from this resin have good resistance to ds, alkalis, and chemicals generally, but not to aromatic solvents, gasoline, etc.
chopped strand - roved fibers that are chopped into short lengths for use in mats, spray-up, or molding compounds.
circuit grouting - a grouting method by which grout is circulated through a pipe extending to the bottom of the hole and back up the hole via the annular space outside the pipe, the excess grout being diverted back over a screen to the agitator tank by means of a packing gland at the top of the hole; used where holes tend to cave and sloughing material might otherwise clog openings to be grouted.
cleanup - treatment of existing concrete substrate to remove all surface material and contamination down to a condition of cleanness corresponding to that of a freshly broken surface of concrete.
closure - achieving the desired reduction in grout take by splitting the hole spacing; if closure is being achieved, there will be a progressive decrease in grout take as primary, secondary, tertiary, and quaternary holes are grouted.
coal tar - a material produced by the destructive distillation of coal; coal tar epoxies are coatings inwhich the binder is a combination of coal tar and epoxy resins.
coating - liquid, with or without fillers or reinforcement, that is applied to a substrate by brushing,dipping, mopping, spraying, troweling, etc., to form a material that will bond to and preserve, protect, decorate, seal, or smooth the substrate; also used to provide a barrier to contain chemicals.
coating, high-build - see high-build coating.
coaxial dispenser - a two-component device that contains one dispensing cartridge within another;plungers for each cartridge are depressed simultaneously to extrude the adhesive components in theproper proportions, usually through a static mixing tube.
coefficient of permeability - the rate of discharge of water under laminar-flow conditions through a unit cross-sectional area of a porous medium under a unit hydraulic gradient and standard temperature conditions (usually 20 C).
coefficient of thermal expansion - change in linear dimension per unit length or change in volume per unit volume per degree of temperature change.
cofferdam - a temporary structure enclosing all or part on a construction area so that construction or repair can proceed in the dry.
cohesion - the state in which the constituents of a mass of material are held together by chemical and physical forces.
cohesive failure - rupture of an adhesive bond such that the separation appears to be within the adhesive.
cold joint - a unplanned joint or discontinuity resulting from a delay in placement of sufficient time to preclude a union of the material in two successive lifts.
cold-weather concreting - special concreting and construction practices used to offset the limitingeffects of cold conditions.
collar - (1) jackets which surround only a portion of a column or pier; typically used to provide increased support to the structural member at the top of the column or pier. (2) the surface opening of a borehole.
colloid - a substance that is in a state of division preventing passage through a semipermeable membrane, consisting of particles ranging from 0.1 to 0.001 µm in diameter.
colloidal grout - see grout, colloidal.
communication - subsurface movement of grout from an injection hole to another hole or opening.
compaction grout - injection grout with less than 1 in. (25 mm) slump; normally a soil-cement with sufficient silt sizes to provide plasticity and sufficient sand sizes to develop internal friction; generally does not enter soil pores but remains in a homogenous mass that provides controlled displacement to compact loose soils or lift structures, or both.
compatibility - (1) a balance of physical, chemical, and electrochemical properties and dimensionsbetween a repair material and the existing substrate; (2) the capacity of two or more materials to combine or remain together without undesirable aftereffects; (3) mutual tolerance.
composite - a product or system that is a combination of individual elements or materials, e.g., a typical composite repair system includes the concrete substrate, the adhesive bonding agent, and the repair material.
composite construction - a type of construction with different materials and structural elements that are sufficiently interconnected that the combined components respond to loads as a unit.
compound - a mixture of a polymer with other ingredients such as fillers, stabilizers, catalysts, processing aids, lubricants, modifiers, pigments, or curing agents.
compression seal - a seal that is attained by a compressive force on the sealing material.
compressive strength - the measured maximum resistance of a test specimen to axial compressive loading; expressed as force per unit cross-sectional area.
concrete - a composite material that consists essentially of a binding medium within which are embedded particles or fragments of aggregate, usually a combination of fine aggregate and coarse aggregate; in portland-cement concrete, the binder is a mixture of portland cement and water.
concrete, epoxy - a mixture of epoxy resin, curing agent, fine aggregate, and coarse aggregate. (See also epoxy mortar, epoxy resins, and concrete, polymer).
concrete, fiber-reinforced - concrete containing dispersed, randomly oriented fibers.
concrete, fresh - unhardened concrete that can be consolidated by the intended method.
concrete, high-early-strength - concrete that contains high-early-strength cement or admixtures which allow it to reach a specified strength earlier than normal concrete would.
concrete, high-strength - concrete that has a specified compressive strength for design of 6000 psi(41 MPa) or greater.
concrete, mass - any volume of concrete with dimensions large enough to require that measures be taken to cope with generation of heat from hydration of the cement and attendant volume change to minimize cracking.
concrete, plain - concrete without reinforcement.
concrete, polymer - a composite material in which the fine and coarse aggregates are bound together in a dense matrix with a polymer binder; also known as resin concrete.
concrete, polymer-modified - a mixture of water, hydraulic cement, aggregate, and a monomer orpolymer; polymerized in place when a monomer is used.
concrete, preplaced-aggregate - concrete produced by placing coarse aggregate in a form and later injecting a portland cement-sand grout, usually with admixtures, to fill the voids.
concrete (mortar, grout), preshrunk - (1) concrete that has been mixed for a short period in a stationary mixer before being transferred to a transit mixer. (2) grout, mortar, or concrete that has been mixed 1 to 3 hr before plng in order to reduce shrinkage during hardening.
concrete, pumped - concrete which is transported through a hose or pipe by means of a pump.
concrete, reinforced - concrete containing adequate reinforcement (prestressed or not prestressed) and designed on the assumption that the two materials act together in resisting forces.
concrete, roller-compacted - concrete compacted by roller compaction; concrete that, in its unhardened state, will support a roller while being compacted.
concrete, structural - concrete used to carry structural load or to form an integral part of a structure; concrete of a quality specified for structural use.
concrete, tremie - concrete placed underwater with a tremie pipe or hose.
concrete breakers - hand-held or machine mounted equipment commonly used for removal of concrete by repeated striking of the surface to spall and fracture the concrete. (See also boom-mounted breakers,
hand-held breakers, impact breakers, and scabblers.)
condensed silica fume - see silica fume.
condition - to equalize the moisture in a material with that of a specified atmosphere.
conductive-polymer mortar - a rigid material formulated by polymerization of a select resin system and conductive petroleum coke which is capable of distributing impressed anodic current; the material is used to fill cut slots, as strips or ribbons in grid-fashion on a bridge deck or structure, or applied as a thin overlay to substructure concrete members to stop the corrosion of reinforcing steel.
conductivity, thermal - see thermal conductivity.
consolidation - the process whereby the volume of freshly placed mortar or concrete is reduced to the minimum practical space, usually by vibration, rodding, tamping, or some combination of these actions; to mold mortar or concrete within a form or repair cavity and around embedded items and reinforcement and eliminate voids other than entrained air. (See also rodding and tamping.)
consolidation grouting - injection of a fluid grout, usually sand, portland cement, and water, into a compressible soil mass in order to displace it and form a lenticular grout structure for support.
onstruction joint - interface between two successive placements; bond is typically required at such joints and reinforcement may be continuous.
contact grouting - see backpack grouting.
contact splice - a means of connecting reinforcing bars in which the bars are lapped and in direct contact.
(See also lap splice.)
continuity, reinforcement - see reinforcement continuity.
continuous mixer - a mixer into which the ingredients of the mixture are fed without stopping, and from which the mixed product is discharged in a continuous stream.
contraction - a drawing together that reduces the volume or length of a mass or object.
control joint - formed, sawed, or tooled groove in a repair surface to create a weakened plane and
regulate the location of cracking resulting from restrained contraction of the repair material.
controlled low-strength material - a self-compacted, cementitious material used primarily as a backfill in lieu of compacted fill.
conveying hose - see delivery hose.
coping - the top layer or a covering on a wall or pier exposed to the weather, usually sloped to carry off water.
copolymerization - see polymerization.
copper-copper sulfate half cell - a commonly used standard reference electrode used to measure the electrical potential between it and the reinforcing steel.
core - a cylindrical sample of hardened concrete or rock obtained by means of a core drill.
core recovery - ratio of the length of core recovered to the length of hole drilled, usually expressed as a percentage.
coring - the process of drilling and extracting cores from concrete structures or rock foundations.
corrosion - degradation of concrete or steel reinforcement caused by electrochemical or chemical attack.
corrosion inhibitor - a chemical compound which, when used as an admixture in fresh concrete or as a topical application to hardened concrete, inhibits corrosion of embedded metal.
corrosion threshold - total chloride or soluble chloride content necessary to initiate corrosion of metals embedded in concrete. Usually assumed to be 1.0 to 1.4 lb/cu yd or approximately 0.4% by wt of cement?
over - (1) in reinforced concrete, the least distance between the surface of the reinforcement and the outer surface of the concrete. (2) in grouting, the thickness of rock and soil material overlying the stage of the hole being grouted.
coverage - the area that a specified volume of coating will cover to a specified dry thickness.
covermeter - a nondestructive testing method for locating embedded steel reinforcement, measuring depth of cover, and estimating the diameter of reinforcement by measuring the change in a low frequency alternating magnetic field applied on the surface of a member.
crack - a complete or incomplete separation of concrete into two or more parts produced by breaking or fracturing.
crack bridging - the ability of repair or protective surface treatment to remain continuous when installed on a cracked concrete surface.
crack injection - a method for sealing or repairing cracks by injecting a polymer.
crack monitor - a device that measures the movement of cracks.
cracks, active - see active cracks.
cracks, dormant - see dormant cracks.
craze cracks - fine random cracks or fissures in a surface.
crazing - the development of craze cracks; the pattern of craze cracks existing in a surface. (See also checking and craze cracks.)
creep - time-dependent deformation resulting from a sustained load.
creep, compressive - creep that occurs because of compressive load.
creep, drying - creep caused by drying.
creep, tensile - creep that occurs because of tensile load.
critical saturation - the condition reached when the degree to which freezable water fills a pore space in cement paste or aggregate affects the response to freezing; usually taken to be 91.7 percent because of the 9 percent increase in volume of water when it changes to ice.
crosshole logging - a nondestructive testing method for locating low-quality concrete with transducers positioned along the length of holes drilled into a deep foundation. (See also ultrasonic pulse velocity.)
cross-linking - the chemical bonding between linear polymer chains to form a three-dimensional network.
crystallization - arrangement of previously disordered material segments of repeating patterns intogeometric symmetry.
cure - the process by which a compound attains its intended performance properties by means of evaporation, chemical reaction, heat, radiation, or combinations thereof.
cure time - the time interval between formation or placement of a material and the materialsÕs reaching specified design properties; some materials require specified treatment during this interval.
curing - the maintenance of a favorable temperature and moisture environment for freshly placed repair materials during some definite period following placing, casting, or finishing so that the desired properties may develop.
curing agent - see catalyst and hardener.
curing compound - a liquid coating that can be applied on fresh cementitious materials to minimize moisture loss or reflect heat so that the properties of a material can develop in a favorable environment.
curling - the distortion of an originally essentially linear or planar member into a curved shape such as the warping of a slab due to creep or to differences in temperature or moisture content in the zones adjacent to its opposite faces. (See also warping.)
curtain grouting - subsurface injection of grout to create a barrier of grouted material transverse to the direction of anticipated water flow.
cutting screed - sharp-edged tool used to trim shotcrete to finished outline. (See also rod.)
damp - either moderate absorption or moderate covering of moisture; implies less moisture than a wet condition and slightly more moisture than a moist condition.
dampproofing - treatment of a material to retard the passage or absorption of water or water vapor either by application of a suitable coating to exposed surfaces or by use of a suitable admixture.
D-cracking - a series of cracks in concrete near and roughly parallel to joints, edges, and structuralcracks.
dead load - a constant load that in structures is due to the mass of the members, the supported structure, and permanent attachments or accessories.
debond - a separation of bonded surfaces.
deflection - movement of a point on a structure or structural element, usually measured as a lineardisplacement transverse to a reference line or axis.
deformation - a change in shape or size.
deformation, time-dependent - deformation caused by time-dependent factors such as autogenousvolume change, thermal contraction or expansion, creep, shrinkage, and swelling.
degradation - a detrimental change in the physical and/or chemical properties of a material.
delamination - a separation along a plane parallel to a surface as in the separation of a coating from a substrate or the layers of a coating from each other, or in the case of a concrete slab, a horizontal splitting, cracking, or separation of a slab in a plane roughly parallel to, and generally near, the upper surface.
delivery equipment - equipment which introduces shotcrete material into the delivery hose.
delivery hose - hose used to place shotcrete, grout, or pumped concrete or mortar; also known as a
conveying hose or material hose.
deterioration - physical manifestation of failure of a material (e.g., cracking, delamination, flaking, pitting, scaling, spalling, staining) caused by service conditions or internal autogenous influences. (See
also disintegration and weathering.)
dew point - the temperature of a surface at a given ambient temperature and relative humidity, at which condensation of moisture will occur.
dewatering - the removal and control of subsurface groundwater from soil or rock formations. (See also unwatering.)
diagonal crack - an inclined or slanted crack that is nonparallel to the transverse or longitudinal axis of a member.
diamond wire cutting - a method for removal of concrete sections with a wire that contains modules impregnated with diamonds; the wire is wrapped around the concrete mass to be cut and connected to a power pack so that it travels in a continuous loop.
differential settlement - a relative variation in rate and/or magnitude of settlement in different areas of a structure.
dimensional compatibility - a balance of dimensions, or volumetric stability, between a repair material and the existing substrate.
direct shear test - a shear test in which a material under an applied normal load is stressed to failure by moving one section of the specimen relative to the other section in direction perpendicular to the applied normal load.
discoloration - fading or other alteration of a color that changes the normal appearance.
disintegration - reduction of a mass to components, fragments, or particles. (See also deterioration and weathering.)
dispenser, coaxial - see coaxial dispenser.
dispersing agent - a material capable of increasing the fluidity of cement paste, mortars, or concrete by reduction of interparticle attraction.
displacement grouting - injection of grout into a formation in such a manner as to move the formation; movement may be controlled or uncontrolled. (See also penetration grouting.)
distortion - see deformation. 16
distress - physical manifestation of cracking and distortion in a structure as the result of stress, chemical action, or both.
dormant cracks - those cracks not currently moving or whose movement is of such magnitude that the repair will not be affected.
dowel - (1) a steel pin, commonly a plain round steel bar, which extends into adjoining portions of a concrete construction, as at a joint in a pavement slab, so as to transfer shear loads; (2) a deformed reinforcing bar intended to transmit tension, compression, or shear through a construction joint.
drain - a pipe or channel used to remove water.
drainage curtain - a row of open holes drilled parallel to and downstream from the grout curtain of a dam for the purpose of reducing uplift pressures.
drainage gallery - an opening or passageway within a concrete structure from which grout holes or drainage holes are drilled. (See also grout gallery.)
drilled-in port - pipe nipple for grout hose connection which is embedded in a short entry hole drilled into the concrete surface.
dry-mix shotcrete - shotcrete to which most of the mixing water is added at the nozzle. (See also
dry pack - very dry portland-cement mortar or polymer-modified mortar usually compacted by ramming.
dry packing - hand placement of very dry mortar and the subsequent tamping or ramming of the mortar into a confined place.
drying shrinkage - shrinkage resulting from loss of moisture.
durability - the ability of a structure or its components to maintain serviceability in a given environment over a specified time.
durability factor - a measurement of the ability of a material to retain its properties over a period of time in which it is exposed to deleterious conditions; usually expressed as percentage of the value of a given property before exposure.
dusting - the development of a powdered material at the surface of a cementitious material.
dye tracer - an additive whose primary purpose is to change the color of grout or water.
dynamic modulus of elasticity - the modulus of elasticity computed from the size, weight, shape, and fundamental frequency of vibration of a concrete test specimen, or from pulse velocity.
efflorescence - a deposit of white salts left on a surface when a solution containing the salts leaches from concrete or masonry and then evaporates.
efflux time - time required for all grout to flow from a flow cone. (See also flow cone.)
elastic modulus - see modulus of elasticity.
elasticity - that property of a material that enables it to return to its original size and shape after deformation.
elastomer - a rubber-like material that returns rapidly to approximately its initial dimensions and shape after removal of the deforming force.
elastomeric - having the characteristics of an elastomer.
electrical resistivity - a measure of the resistance of a material to flow of electric current.
electric log - a record or log of a borehole obtained by lowering electrodes into the hole and measuring any of the various electrical properties of the materials traversed.
electrochemical chloride extraction - removal of chlorides from concrete by application of a direct current that causes chlorides to migrate to the concrete surface.
electrochemical compatibility - a balance of electrochemical properties of two materials in contact.
electrolysis - production of chemical changes by the passage of current through an electrolyte.
electrolyte - a conducting medium in which the flow of current is accompanied by movement of matter; usually an aqueous solution.
electrolytic cell - a unit apparatus in which electrochemical reactions are produced by applying electrical energy, or that supplies electrical energy as a result of chemical reactions and that includes two or more electrodes and one or more electrolytes contained in a suitable vessel.
elephant trunk - an articulated tube or chute used in concrete placement.
elongation - increase in length.
emulsion - a two-phase liquid system in which one liquid is immiscible in and uniformly dispersedthroughout another liquid.
endothermic reaction - a chemical reaction in which heat is absorbed.
envelope grouting - grouting of rock surrounding a hydraulic pressure tunnel to consolidate the rock and reduce permeability of the area.
epoxy injection - a method for sealing or repairing cracks in concrete by injecting epoxy adhesives.
epoxy mortar - a mixture of epoxy resin, curing agent, and fine aggregate.
epoxy resins - a class of organic chemical bonding systems used in the preparation of special coatings for concrete, adhesives for injection of cracked concrete, or as binders in epoxy-resin mortars and concretes.
erosion - progressive disintegration of a solid by the abrasive or cavitation action of gases, fluids, or solids in motion. (See also abrasion damage and cavitation damage.)
ettringite - a mineral, high-sulfate calcium sulphoaluminate, occurring in nature or formed by sulfate attack on mortar or concrete.
ester - a class of compounds formed by the reaction of alcohols and organic acids.
evaluation - the process of determining the need for maintenance, repair, or rehabilitation of concrete and concrete structures by identifying the cause and extent of distress or deterioration. (See also repair, maintenance, and rehabilitation.)
evaporable water - water in set cement paste that can be removed by specified drying conditions. (See also non-evaporable water.)
exfoliation - disintegration by scaling or peeling off in thin flakes; corrosion along planes parallel to the surface that forces metal away from the body of the material resulting in a layered appearance.
exotherm - heat released during a chemical reaction.
exothermic reaction - a chemical reaction in which heat is evolved.
expansion - increase in either length of volume.
expansion anchors - anchor systems which develop their strength from friction against the side of the drilled hole, from keying into a localized crushed zone of the concrete resulting from the setting operation, or keying into an undercut at the bottom of the drilled hole, or from a combination of friction and keying; includes torque-controlled, deformation-controlled, and undercut anchors.
expansive cement - see cement, expansive.
extender - a finely divided inert mineral or coarse aggregate added to provide economical bulk in
synthetic resins and adhesives or cementitious mortars.
extensibility - the maximum tensile strain that hardened cement paste, mortar, or concrete can sustain without formation of a continuous crack.
extensometer points - an arrangement of three embedded plugs or surface-mounted discs, two on one side of a crack and the third on the other, which, when used in combination with a mechanical strain gage, provides a technique for monitoring crack width.
external strengthening - the bonding or anchoring of reinforcing elements, e.g., steel plates, fiberreinforced plastics, and external posttensioning, on the exterior of structural members to increase structural capacity.
explosive blasting - a method for fracturing and removing concrete with rapidly expanding gas confined within a series of bore holes; a cost effective and expedient means for removing large quantities of concrete.
exudation - a liquid or viscous gel-like material discharged through a pore, crack, or opening in the surface of concrete.
failure - a point at which a material stops performing as it was intended to.
failure, adhesive - see adhesive failure.
false set - the rapid development of rigidity in a freshly mixed portland cement paste, mortar, or concrete without the evolution of much heat, which rigidity can be dispelled and plasticity regained by further mixing without addition of water.
fascia - a flat member or band at the surface of a building or the edge beam of a bridge; also exposed eave of a building.
fatigue - the weakening or failure of a material subjected to prolonged or repeated stress.
faulting - a crack or joint in a surface along which there has been relative vertical displacement of the two sides parallel to the discontinuity.
feather edge - to smoothly blend the edge of a repair or topping into the existing concrete at an acute angle.
feed wheel - material distributor or regulator in certain types of shotcrete equipment.
fiber mat - a fibrous reinforcing material composed of chopped filaments (for chopped-strand mat) or swirled filaments (for continuous-strand mat) with a binder applied to maintain form; available in blankets of various widths, weights, thicknesses, and lengths.
fiber-reinforced composite - any composite material consisting of a matrix reinforced by continuous or discontinuous fibers.
fiber-reinforced plastics (FRP) - a general term for a composite material or part that consists of a resin matrix containing reinforcing fibers such as glass or carbon having greater strength or stiffness than the resin; FRP is most often used to denote glass fiber-reinforced plastics while the term advanced composite usually denotes high-performance aramid or carbon fiber-reinforced plastics.
fibrous concrete - see concrete, fiber-reinforced.
field-cured cylinders - test cylinders that are left at the jobsite for curing as nearly as practicable in the same manner as the repair material to indicate when supporting forms may be removed, additional construction loads may be imposed, or the structure may be placed in service.
field-molded sealant - a liquid or mastic sealant that is shaped by the joint into which it is placed.
filaments - individual fibers of indefinite lengths used in tows, yarns, or roving.
filler - a general term for an inert material that occupies space and may improve physical properties or lower cost. (See also extender.)
film - a thin coating over the surface of a material.
finish coat - the final thin coat of shotcrete applied prior to hand finishing. (See also flash coat.)
finishing - leveling, smoothing, consolidating, and otherwise treating the surface of a repair material to produce the desired appearance.
fissure - a narrow opening, crack, or separation on a concrete surface.
flash coat - a thin coat of shotcrete applied from a distance greater than normal for use as a final coat or for finishing.
flash point - the lowest temperature of a liquid at which sufficient vapor is provided to form an ignitable mixture when combined with air.
flexural strength - the property of a solid that indicates its ability to resist failure in bending. (See also modulus of rupture.)
fouling - marine growth such as barnacles adhering to a substrate.
form and pump - repair method for vertical and overhead repairs in which a formed cavity is filled with mortar or concrete under pump pressure.
flow - a measure of the consistency of freshly mixed concrete, mortar, or cement paste in terms of the increase in diameter of a molded, truncated cone specimen after that has been jiggled a specified number of times.
flow line - a defect induced by discontinuous flow velocities and lack of proper consolidation during placement of concrete by pumping.
fluidifier - an admixture employed in grout to decrease the flow factor without changing water content. (See also water reducer.)
fly ash - the finely divided residue resulting from the combustion of pulverized coal in electric power generating plants.
fly ash, Class C - ash normally produced by burning sub-bituminous coal or lignite; usually has
significant cementitious properties in addition to pozzolanic properties, particularly those ashes with CaO contents of 15 to 30 percent.
fly ash, Class F - ash usually produced by burning anthrte or bituminous coal; ashes generally have CaO contents less than 10 percent and are rarely cementitious when mixed with water alone.
fog curing - application of atomized fresh water to cementitious repair materials.
form - a temporary structure or mold for the support of a repair while it is curing and gaining sufficient strength to be self-supporting.
form lining - materials used to line the interior face of formwork in order to impart a smooth or patterned finish to the repair surface, to absorb moisture from the repair material, or to apply a set-retarding chemical to the formed surface.
form scabbing - inadvertent removal of the surface of a repair material because it had adhered to the form.
fracture - a crack or break, as of concrete, or a rock mass; the configuration of a broken surface; also the action of cracking or breaking. (See also crack.)
friction - force that resists the relative motion of two surfaces in contact.
full-depth repair - removal and replacement of damaged or deteriorated concrete that constitutes the full depth of a member or element.
fungicide - a substance poisonous to fungi used to retard or kill mold and mildew growth.
furan resin - a thermosetting catalyzed condensation reaction product from furfuryl alcohol, furfural or combination thereof.
fuzzy - a hairy appearance caused by protruding broken fibers or filaments.
gage length - the original length of that portion of a specimen or structure over which a deformation measurement is made.
galvanic corrosion - accelerated corrosion of a metal because of an electrical contact with a more noble metal or nonmetallic conductor in a corrosive electrolyte.
gel - (1) matter in a colloidal state that does not dissolve, but remains suspended in a solvent from which it fails to precipitate without the intervention of heat or of an electrolyte. (2) the condition where a liquid grout begins to exhibit measurable shear strength.
gel time - the time interval between mixing the constituents of a liquid material and the formation of a gel.
geomembrane - a flexible, watertight polymeric membrane with a thickness of one-half to a few
millimeters; a wide range of polymers, including plastics, elastomers and blends of polymers are used to manufacture geomembranes.
geonet - a geosynthetic consisting of integrally connected parallel sets of ribs overlying similar sets at various angles for planar drainage of liquids and gases.
glass fibers - reinforcing fiber made by drawing molten glass through bushings; the predominant reinforcement for polymer matrix composites, known for its good strength, process ability, and low cost.
glass-fiber reinforced cement - a composition material consisting essentially of a matrix of hydraulic cement paste or mortar reinforced with glass fibers; typically precast into units less than 1-in. (25-mm) thick.
glass-transition temperature - the midpoint of the temperature range over which an amorphous material (such as glass or a high polymer) changes from (or to) a brittle, vitreous state to (or from) a plastic state.
go-devil - a ball of rolled-up burlap or a specially fabricated device placed in a tremie pipe immediately prior to introduction of the concrete to keep the concrete from mixing with water in the pipe as the concrete flows to the bottom of the pipe.
gravity feed - the movement of materials from one container to another container or location by force of gravity.
gravity grouting - grouting by using only the height of the fluid column to provide pressure.
gravity soak - method for repair of cracks in horizontal concrete sections by topical application of a low viscosity resin.
grinding - the removal of thin coatings, mineral deposits, or slight protrusions on a concrete surface with rotating abrasive stones or discs under pressure at right angles to the surface.
grit blasting - abrasive blasting with small irregular pieces of steel or malleable cast iron.
groove joint - a joint created by forming a groove in the surface of a repair to control random cracking.
grooving - a process in which narrow parallel channels are cut into the surface of a material to improve drainage and skid resistance of surfaces subjected to traffic.
ground penetrating radar - see short-pulse radar.
ground wire - small-gage high-strength steel wire used to establish line and grade as in shotcrete work; also called alignment wire and screed wire.
grout - a mixture of cementitious material and water, with or without aggregate, proportioned to produce a pourable consistency without segregation of the constituents; also a mixture of other composition but of similar consistency.
groutability - the ability of a formation to accept grout.
grout cap - a cap that is formed by placing concrete along the top of a grout curtain; often used in weak foundation rock to secure grout nipples, control leakage, and form an impermeable barrier at the top of a grout curtain.
grout, colloidal - grout in which a substantial proportion of the solid particles have the size range of a colloid.
grouting - the process of injecting or placing grout.
grout gallery - an opening within a dam used for grouting or drainage operations.
grout header - a pipe assembly attached to a ground hole, and to which lines for injecting grout are attached; sometimes called a grout manifold.
grout mixture - the proportions or amounts of the various materials used in the grout, expressed by weight or by volume.
grout nipple - a short length of pipe installed at the collar of the grout hole to facilitate drilling grout injection.
grout slope - the natural slope of fluid grout injected into preplaced-aggregate concrete.
grout system - combination of materials used in a specified grout mixture.
grout take - the measured quantity of grout injected into a unit volume of formation, or a unit length of grout hole.
guideline - a written statement of policy or procedure.
gun - delivery equipment that pneumatically places shotcrete and freshly mixed concrete.
gun casting - a procedure in which concrete or mortar is placed with a special velocity-reducing casting head and standard shotcrete delivery equipment.
gun finish - undisturbed final layer of shotcrete as applied from nozzle, without hand finishing.
Gunite - a proprietary term for shotcrete.
gunman - workman on shotcreting crew who operates delivery equipment.
gunning - pneumatically projecting shotcrete onto surface to be gunned.
gunned pattern - (1) conical outline of material discharge stream in shotcrete operation; (2) the sequence of gunning operations to insure complete filling of the space, total encasement of reinforcing bars, easy removal of rebound, and thickness of shotcrete layers.
hairline cracks - cracks in an exposed concrete surface that are barely visible because of their extremely narrow widths.
halo effect - see anodic ring effect.
half-cell potential - a nondestructive testing method for identifying regions in a reinforced concrete structure where there is a high probability that corrosion is occurring at the time of test by measuring the potential difference (voltage) between the steel reinforcement and a standard reference electrode; a copper-copper sulfate half cell is commonly used on bridge decks.
Hamm tip - flared shotcrete nozzle having a larger diameter at midpoint than at either inlet or outlet; also designated premixing tip.
hand-held breakers - equipment commonly used for removal of concrete by repeated, low-energy and high-frequency striking of the surface to spall and fracture the concrete. (See also boom-mounted
breakers, impact breakers, and scabblers.)
hardener - in a two-component adhesive or coating, the chemical component that causes the resincomponent to cure.
hardness - the resistance of a material to deformation, particularly permanent deformation, indentation, or scratching.
heat-deflection temperature - the temperature at which a plastic material has an arbitrary deflection when subjected to an arbitrary load and test condition; this is an indication of the glass-transition temperature.
heat of hydration - heat evolved during the setting and hardening of portland cement.
heat of solution - heat emitted or absorbed by a substance being dissolved in a solvent.
high-build coating - protective surface treatment with a dry thickness greater than 10 mils (0.25 mm) and less than 30 mils (0.75 mm) applied to the surface of concrete.
high-molecular weight methacrylate - a low-viscosity substituted methacrylate monomer that is characterized by low volatility.
high-pressure water blasting - a process for cleaning, or roughening with a stream of water under high pressure that contains an abrasive such as sand, aluminum oxide, or garnet.
high-pressure water jets - water jets with a force capable of selectively cutting through deteriorated concrete; widely used as a surface preparation method in concrete repair.
high-range water reducer - a water-reducing admixture capable of producing large water reduction or great flowability without causing undue set retardation or entrainment of air in mortar or concrete.
holiday - a discontinuity in a coating material that exposes the substrate.
hollow-core bit - carbide-tipped drills with internal ports for water flushing or vacuum extraction of cuttings during drilling; used in drilling deep injection ports to minimize plugging of internal cracks intersected by drill hole.
homogenous material - a material that exhibits essentially the same physical properties throughout the material.
honeycomb - voids in concrete created when the mortar does not fill all the spaces among coarse aggregate particles.
humidity, relative - see relative humidity.
hybrid composite - a composite made with two or more types of reinforcing fibers.
hydration - combining water with another substance to create a compound; in concrete, the chemical
reaction between hydraulic cement and water.
hydraulic splitting - a method for removal of concrete by means of hydraulic forces that split concrete into smaller masses.
hydro nozzle - a special prewetting and mixing nozzle consisting of a short length of delivery hoseinserted between the nozzle body and nozzle tip.
hydrodemolition - a method for removal of concrete by means of water under high pressure directed against a surface; provides a sound concrete substrate and cleans steel reinforcement for reuse.
hydrogen embrittlement - cracking or loss of ductility caused by hydrogen in a metal.
hydrophilic - material which exhibits a strong affinity for water; wettable.
hydrophobic - material which does not exhibit affinity for water; tends to repel water.
hydrostatic head - the fluid pressure of a liquid produced by the height of that liquid above a given point.
hygrometer - an instrument used to measure humidity.
hygroscopic - material that readily absorbs and retains moisture from the air.
impact - instantaneous contact of a moving body with another body, either moving or at rest.
impact breakers - equipment for removal of concrete by repeated striking of the surface to spall and fracture the concrete; may produce microcracking in the concrete substrate. (See also hand-held breakers, boom-mounted breakers, and scabblers.)
impact echo - a nondestructive testing method, based on stress wave propagation, that uses impact to generate a low frequency wave; the presence and position of a reflector, such as a crack, delamination, or void, are indicated by the echo amplitude and time.
impact resistance - resistance to fracture under the sudden application of an external force.
impending slough - a consistency of a shotcrete mixture containing the maximum amount of water such that the product will not flow or sag after placement.
impregnation - a process in which the void structure of a hardened material is filled by saturation with a liquid.
impulse radar - a nondestructive testing procedure that uses low-power impulse radar elements and advanced signal processing techniques to detect and image the internal structure of reinforced concrete.
incompatible - a condition in which two or more materials are unable to combine or remain together without undesirable aftereffects.
incrustation - a crust or coating, generally hard, formed on the surface of hardened concrete.
induction time - the time between mixing of two-component materials and the time they can be used.
inert - devoid of active properties; incapable of or resisting combination.
infrared thermography - a nondestructive testing method for locating delaminations in pavements and bridge decks and detecting moist insulation in buildings; the presence of flaws within concrete affects the heat conduction properties of the concrete and the presence of defects is indicated by differences in surface temperatures when the test object is exposed to correct ambient conditions.
infiltration - the uncontrolled ingress of air or liquid through cracks and pores in concrete.
inhibitor - a substance that slows chemical reaction.
initiator - a substance capable of causing a chemical reaction (such as polymerization or curing) to start.
injection grouting - a method for sealing or repairing cracks in concrete and filling voids within aconcrete structure or foundation.
injection port - entry point where grout is introduced into cracks and voids.
inspection, visual - see visual inspection.
interface - the common boundary surface between two materials, e.g., an existing concrete substrate and a bonded repair material.
intumescent coating - a fire retardant coating which, when heated, produces nonflammable gases that convert the coating to a foam, thereby insulating the substrate.
isotropic material - a material that exhibits the same properties in all directions.
jacket - an integral covering which is applied over an existing structural element, e.g. a concrete pile, whose primary function is to strengthen or provide environmental protection, or both.
jackhammer - hand-held mechanical breaker for removal of concrete.
jaw crusher - boom-mounted mechanical crusher for removal of concrete from decks, walls, columns, and other concrete members where the shearing plane depth is 6 ft (1.8 m) or less; pulverizing jaw attachment can debond concrete from steel reinforcement for recycling purposes. (See also mechanical shearing.)
joint - a physical separation in concrete, including cracks if intentionally made to occur at specified locations.
joint filler - compressible material used to fill a joint to prevent the infiltration of debris and to provide support for sealants.
joint sealant - compressible material used to prevent water and debris from entering joints.
joint spall - a fragment detached from a concrete mass adjacent to a joint.
jumbo - a specially built mobile carrier used to provide a work platform for tunneling operations, such as installing rock bolts and grouting.
kerf - a saw cut in a concrete surface for embedment of the perimeter of a membrane or other thin surface treatment.
keyway - a recess or groove in a concrete substrate which is filled with repair material to provide increased shear strength along the interface.
laitance - a thin layer of weak and nondurable material containing cement and fines, brought to the top of overwet concrete and other cementitious repair materials by bleeding water or improper finishing.
laminate - to bond layers of a material.
lance - equipment for shooting refractory shotcrete material into areas that have a high temperature; typically, a length of metal pipe with an extended nozzle with various configurations.
latex - a stable emulsion of natural or synthetic rubber in water.
latex-modified concrete - see concrete, polymer-modified.
leakage - the quantity of material that accidentally enters or escapes through an opening such as a hole or crack.
length change - increase or decrease in length. (See also volume change and deformation.)
lift - individual layer of repair material where several layers or courses are required to achieve the total depth of a repair.
lifting - softening and raising or wrinkling of a pervious coat by the application of an additional coat; often caused by coatings containing strong solvents.
linear polarization - a nondestructive testing method to determine the instantaneous corrosion rate of the concrete reinforcement located below the test point by measuring the current required to change by a fixed amount the potential difference between the reinforcement and a standard reference electrode.
lining - any protective material applied to the interior surface of a conduit, pipe, or tunnel to provide watertightness, erosion resistance, chemical resistance, or reduced friction.
liquid-volume measurement - measurement of grout on the basis of the total volume of solid and liquid constituents.
live load - a moving load on a structure.
load cell - device for measuring the magnitude of an applied load.
longitudinal crack - crack that generally parallels the length of a member.
lot - a definite quantity of a product or material accumulated under conditions that are considered uniform for sampling purposes.
lubricity - in grouting, the physico-chemical characteristic of a grout material flow through a soil or rock that is the inverse of the inherent friction of that material to the soil or rock; comparable to wetness.