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Concrete Repair Terminology (F)
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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

- F -

factor of safety

the ratio of capacity to demand for a structure or structural element.


a point at which a material stops performing as it was intended to.

failure, adhesive

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 failure, cohesive.)

failure, cohesive

rupture of an adhesive bond such that the separation appears to be within the adhesive.

failure mode

1) the manner in which a system fails; 2) as related to tensile bond testing, a description of the location and characteristics of failure within a repair composite.

false set

see set, false. (See also set, flash.)


a flat member or band at the surface of a building or the edge beam of a bridge; also exposed eave of a building.


the weakening or failure of a material subjected to prolonged or repeated stress.


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.


slender and greatly elongated solid materials, generally with a length at least 100 times its diameter, that has properties making it desirable for use as reinforcement.

fibers, carbon

reinforcing fiber with light-weight, high-strength, and high-stiffness characteristics produced by oxidizing organic polymer fibers.

fibers, glass

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.

fibers, polyolefin

manufactured fibers in which the fiber-forming substance is any long-chain synthetic polymer composed of at least 85% by weight of ethylene, propylene, or other olefin units, except amorphous (noncrystalline) polyolefins.

fibers, polypropylene

highly chemically inert, long-chain synthetic polymer; fibrillated and monofilament fibers for concrete reinforcement.

fibers, steel

small discontinuous fibers for random dispersion within cementitious materials; typical fiber shapes include round, oval, rectangular, and crescent cross sections, depending on the manufacturing process and raw material used.

fibers, synthetic

polymeric fibers, such as polypropylene, polyolefin, nylon, polyethylene, polyester, and acrylic, that can be used in fiber-reinforced cementitious materials and protective coating systems.

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 polymer (FRP)

a general term for a composite material comprising a polymer matrix reinforced with fibers in the form of fabric, mat, strands, or any other fiber form.

fibrous concrete

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


individual fibers of indefinite lengths used in tows, yarns, or roving.


a general term for an inert material that occupies space and may improve physical properties or lower cost. (See also extender.)


a thin coating over the surface of a material.


the texture or appearance of a surface after placement and finishing operations have been performed.

finish, broom

the surface texture obtained by stroking a broom over freshly placed concrete or other material.

finish, coat

the final thin coat of shotcrete applied prior to hand finishing. (See also flash coat.)

finish, exposed-aggregate

a decorative finish for concrete achieved by removing, usually before the concrete has fully hardened, the outer skin of mortar and exposing the coarse aggregate.

finish, gun

undisturbed final layer of shotcrete as applied from nozzle, without hand finishing.

finish, trowel

the smooth or textured finish of an unformed concrete surface obtained by troweling.


leveling, smoothing, consolidating, and otherwise treating the surface of a material to produce the desired appearance.


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.

flash set

see set, flash. (See also set, false.)

flaw detection

detection of internal defects including voids, under-consolidated concrete and cracking.

flexural strength


a tool (not a darby), usually of wood, aluminum, or magnesium, used in finishing operations to impart a relatively even but still open texture to an unformed fresh concrete surface. (320.5R-14, ACI Concrete Terminology 2013)

float, angle

a finishing tool having a surface bent to form a right angle; used to finish reentrant angles. (320.5R-14)

float, bull

a tool comprising a large, flat, rectangular piece of wood, aluminum, or magnesium, usually 8 in (200 mm) wide and 42 to 60 in (1 to 1.50 m) long, and a handle 4 to 16 ft (1.2 to 5 m) in length used to smooth unformed surfaces of freshly placed concrete. (320.5R-14, ACI Concrete Terminology 2013) After screeding, used as a tool for the first stage in the final finish of concrete to smooth and level hills and voids left after screeding. A bull float is sometimes substituted for darbying.

float, devils

a wooden float with two nails protruding from the toe used to roughen the surface of a brown plaster coat. (320.5R-14, ACI Concrete Terminology 2013)

float, rotary


1) time-dependent irrecoverable deformation (see also creep); 2) a measure of the consistency of freshly mixed concrete, mortar, or cement paste expressed in terms of the increase in diameter of a molded truncated cone specimen after jigging a specified number of times; or 3) movement of uncured resin under gravity loads or differential pressure.

flow cone

a device for measurement of grout consistency in which a predetermined volume of grout is permitted to escape through a precisely sized orifice, the time of efflux (flow factor) being used as the indication of consistency; also the mold used to prepare a specimen for the flow test.

flow line

a defect induced by discontinuous flow velocities and lack of proper consolidation during placement of concrete by pumping.


an admixture employed in grout to decrease the flow factor without changing water content. (See also admixture, water reducing.)

fly ash

the finely divided residue resulting from the combustion of 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%.

fly ash, Class F

ash usually produced by burning anthracite or bituminous coal; ashes generally have CaO contents less than 10% and are rarely cementitious when mixed with water alone.

fog curing

application of atomized fresh water to cementitious repair materials.


a temporary structure or mold for the support of a repair while it is curing and gaining sufficient strength to be self-supporting.

form and pour

the placement of a repair material through gravity flow into an enclosed space with formwork defining exposed boundaries.

form and pump

the placement of repair material using mechanical pumping equipment into an enclosed space with formwork defining exposed boundaries.

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.


marine growth such as barnacles adhering to a substrate.


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.)


force that resists the relative motion of two surfaces in contact.

FRP Engineer

a Licensed Design Professional responsible for designing and detailing an FRP system to meet the design requirements of a project. (330.2-16)

FRP system

1) a system of fiber reinforced polymer materials potentially including various fiber and polymer types and various application methods; 2) a system of fiber reinforced polymer materials designed to satisfy the requirements of a specific project. (330.2-16)

full-depth repair


a substance poisonous to fungi used to retard or kill mold and mildew growth.

furan resin


a hairy surface appearance caused by protruding broken fibers or filaments.

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