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Concrete Repair Terminology (G)
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Concrete Repair Terminology is prepared by the International Concrete Repair Institute. The cross-referenced terms provide definitions for commonly used words in concrete repair, restoration and protection.

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Revised April 2019

A   |   B   |   C   |   D   |   E   |   F   |   G   |   H   |   I   |   J-L   |   M   |   N-O   |   P   |   Q-R   |   S   |   T   |   U-V   |   W   |   X-Y-Z

- G -

gage length

the original length of that portion of a specimen or structure over which a deformation measurement is made.

galvanic cell

a cell which generates an electrical current, consisting of dissimilar metals in contact with each other and with an electrolyte.

galvanic corrosion

accelerated corrosion of a metal because of an electrical contact with a more noble metal or a more noble nonmetallic conductor in a corrosive electrolyte.


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.

general corrosion


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.


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

glass-fiber reinforced cement

a composite 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

midpoint in transition over which a polymer resin changes from a glassy state to a viscoelastic state as measured pursuant to ASTM D4065.

global stability

the stability of the overall structure with respect to uplift, overturning, sway instability or sliding failure; global stability failures result in the collapse of a structure.


a ball of rolled-up burlap or paper or a specially fabricated device put into the pump end of a pipeline or tremie pipe immediately prior to introduction of the concrete and forced through the pipe to keep the concrete from mixing with water in the pipe as the concrete flows to the bottom of the pipe; also used to clean pipelines and tremie pipes.

gravity feed

1) the movement of material from one container or location to another by force of gravity alone; 2) a process of repairing concrete cracks in horizontal surfaces only, by applying low-viscosity epoxy to the surface of the crack and allowing the epoxy to flow down into the crack to fill the crack, using gravity alone and not injecting under pressure into the crack. (210.1R-16)

gravity grouting

gravity soak

method for repair of cracks in horizontal concrete sections by topical application of a low viscosity resin.


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

see joint, contraction (preferred term).


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

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.


a fluid mixture of cementitious or polymer materials used as a filler for cracks or other voids in concrete or foundations such as soil or rock.

grout, cementitious

a mixture of cementitious material and water, with or without aggregate, proportioned to produce a pourable consistency without segregation of the constituents.

grout, chemical

any materials, including sodium silicate, acrylate, lignin, urethane, and resin characterized by being a true solution; no particles in suspension. (See also grout, particulate.)

grout, colloidal

grout in which a substantial proportion of the solid particles have the size range of a colloid.

grout, compaction

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 homogeneous mass that provides controlled displacement to compact loose soils or lift structures, or both.

grout, exothermic

grout that produces heat when the binder and catalyst react; peak exothermic reaction temperature occurs when the grout changes from a liquid to a solid.

grout, neat cement

a mixture of hydraulic cement and water.

grout, organic

grouts that gel or set by chemical reaction. (See also grout, chemical.)

grout, particulate

any grouting material characterized by undissolved (insoluble) particles in the mix. (See also grout, chemical.)

grout, sanded

a grout mixture that contains fine aggregates.

grout, sodium silicate

a commonly used chemical grout system based on reacting a silicate solution to form a gel that binds soil or sediment particles and fills voids.

grout, water-activated

a class of injection grouts that react with water to form polyurethane polymers.


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 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 injection

the process of pumping grout under pressure to fill cracks, and voids.

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 grout injection.

grout penetrability

a grout property descriptive of its ability to fill a porous mass; primarily a function of lubricity and viscosity.

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.


the process of injecting, filling, or displacing a volume with grout.

grouting, advancing-slope

a grout injection technique that causes the leading edge of a mass of grout to move horizontally through preplaced aggregate.

grouting, contact

filling the annular space between a permanent tunnel lining and the surrounding formation with grout.

grouting, blanket

a method for reducing the permeability and strengthening the upper layers of bedrock by drilling and grouting shallow, closely spaced holes according to a grid pattern.

grouting, circuit

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.

grouting, curtain

subsurface injection of grout to create a barrier of grouted material transverse to the direction of anticipated water flow.

grouting, displacement

injection of grout in such a manner as to physically move material adjacent to the point of grout injection. (See also grouting, penetration.)

grouting, envelope

grouting of rock surrounding a hydraulic pressure tunnel to consolidate the rock and reduce permeability of the area.

grouting, gravity

grouting by using only the height of the fluid column to provide pressure

grouting, injection

a method for sealing or repairing cracks in concrete and filling voids within a concrete structure or foundation.

grouting, jet

technique utilizing a special drill bit with horizontal and vertical high-speed water jets to excavate alluvial soils and produce hard, impervious columns by pumping grout through the horizontal nozzles that jets and mixes with foundation material as the drill bit is withdrawn.

grouting, open-circuit

a grouting system with no provision for recirculation of grout to the pump

grouting, penetration

filling joints or fractures in rock or pore spaces in soil with a grout without disturbing the formation; this grouting method does not modify the solid formation structure. (See also grouting, displacement.)

grouting, perimeter

injection of grout, usually at relatively low pressure, around the periphery of an area which is subsequently to be grouted at greater pressure; intended to confine subsequent grout injection within the perimeter.

grouting, permeation

filling joints or fractures in rock or pore spaces in soil with a grout, without disturbing the formation.

grouting, series

similar to stage grouting, except each successively deeper zone is grouted by means of a newly drilled hole, eliminating the need for washing grout out before drilling the hole deeper.

grouting, slush

application of cement slurry to surface rock as a means of filing cracks and surface irregularities or to prevent slaking; also applied to riprap to form grouted riprap.

grouting, stage

sequential grouting of a hole in separate steps or stages in lieu of grouting the entire length at once; holes may be grouted in ascending stages by using packers or in descending stages downward from the collar of the hole.


a written statement of policy or procedure.


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


a proprietary term for shotcrete.


workman on shotcreting crew who operates delivery equipment.


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.

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