vacuum blasting—a closed-loop abrasive blasting process whereby blasting material and associated debris are contained with a vacuum. (See also shotblasting.)
vacuum concrete—see concrete, vacuum.
vacuum dewatering—see concrete, vacuum.
vacuum impregnation—a repair process in which a vacuum applied to a concrete section causes polymers such as epoxy to impregnate the concrete surface or fill cracks and voids within the section.
vacuum saturation—see saturation, vacuum.
valve bag—paper bag for cement or other material, either glued or sewn, made of four or five plies of kraft paper and completely closed except for a self-sealing paper valve through which the contents are introduced and released.
vapor barrier—see barrier, vapor.
vapor pressure—a component of atmospheric pressure; caused by the presence of vapor; expressed in inches, centimeters, or millimeters of height of a column of mercury; or, in SI, in pascals.
vapor retarder—a material that minimizes transmission of water vapor but is not 100% effective in preventing its passage.
variation—see coefficient of variation and standard deviation.
vebe apparatus—an apparatus for measuring workability of very low-slump or no-slump concrete, including a vibrating table, a sample container, and other ancillary items, that permits measurement of the time (vebetime) required to be consolidated in a mold.
vehicle—the liquid portion of coating in which pigment is dispersed; composed of binder and thinner.
velocity, pulse—the velocity at which compressional waves are propagated through a medium.
velocity, settling— the terminal rate of fall of a particle through a fluid as induced by gravity or other external force; the rate at which frictional drag balances the accelerating force (or the external force).
veneer—a masonry facing that is attached to the backup, but not so bonded as to act with it under load.
Venetian—a type of terrazzo topping that incorporates large chips of stone.
vent—a hole or small-diameter pipe used in concrete construction to permit escape of air in a structure being concreted or grouted; also used to monitor the flow of grout.
vented form—see form, vented.
vermiculite—a micaceous mineral; also a group name for certain platy minerals, hydrous silicates of aluminum, magnesium, and iron, characterized by marked exfoliation on heating; also a constituent of clays.
vermiculite concrete—see concrete, vermiculite.
vertical-shaft mixer—see mixer, vertical-shaft.
vibrated concrete—see concrete, vibrated.
vibration—energetic agitation of freshly mixed concrete during placement by mechanical devices, either pneumatic or electric, that create vibratory impulses of moderately high frequency to assist in consolidating the concrete in the form or mold. (1) external vibration employs vibrating devices attached at strategic positions on the forms and is particularly applicable to manufacture of precast items and for vibration of tunnel-lining forms; in manufacture of concrete products, external vibration or impact may be applied to a casting table; (2) internal vibration employs one or more vibrating elements that can be inserted into the fresh concrete at selected locations, and is more generally applicable to in-place construction; and (3) surface vibration employs a portable horizontal platform on which a vibrating element is mounted.
vibration limit—see limit, vibration.
vibration modal analysis—the breaking down of a set of vibrations in a structure or component into independent frequencies and amplitudes.
vibrator—an oscillating machine used to agitate freshly-mixed materials such as concrete or mortar to produce a uniform material without gross voids, and to produce intimate contact with the substrate, boundary of repair cavity, form surfaces, and embedded materials. (See also vibration.)
vibrator, external—see vibrator.
vibrator, spud—a vibrator, having a vibrating casing or a vibrating head, used to consolidate freshly placed concrete by insertion into the mass.
vibrator, surface—a vibrator used for consolidating concrete by application to the surface of a mass of freshly mixed concrete; four principal types exist: vibrating screeds, pan vibrators, plate or grid vibratory tampers, and vibratory roller screeds.
Vicat apparatus—a penetration device used in the testing of hydraulic cements and similar materials.
Vicat needle—see needle, Vicat.
vinyl ester resin—see resin, vinyl ester.
viscometer—instrument used for measuring viscosity of slurries, mortars, or concretes.
viscometer, torque—an apparatus used for measuring the consistency of slurries in which the energy required to rotate a device suspended in a rotating cup is proportional to viscosity.
viscosity—the property of a material that resists change in the shape or arrangement of its elements during flow, and the measure thereof.
viscosity modifier—see admixture, viscosity modifying.
visual concrete—see concrete, architectural and concrete, exposed.
visual inspection—an evaluation procedure in which a qualified investigator observes, classifies, and documents deterioration or distress on exposed concrete surfaces; typically, one of the first steps in evaluation of a concrete structure.
void—cavity enclosed within an otherwise solid mass; may be intentionally or unintentionally formed and may be filled with air, water, or other gaseous or liquid material.
void ratio—the ratio of the volume of void space to the volume of solids.
voids, surface—cavities visible on the surface of a solid. (See also bug holes.)
volatile content—the percentage of materials which evaporate from a coating.
volatile material—material that is subject to release as a gas or vapor; liquid that evaporates readily.
volatile organic compounds (VOC)—a measure of the total amount of organic compounds evaporating from a coating film, excluding water.
volume, absolute—in the case of solids, the displacement volume of particles themselves, including their permeable and impermeable voids, but excluding space between particles; in the case of fluids, their volume.
volume, dry-rodded—the bulk volume occupied by a dry aggregate compacted by rodding under standardized conditions; used in measuring density of aggregate.
volume batching—measuring the constituents of mortar or concrete by volume.
volume change—an increase or decrease in volume of a material. (See also deformation and deformation, time-dependent.)
volume change, autogenous—change in volume produced by continued hydration of cement, exclusive of effects of applied load and change in either thermal condition or moisture content.
volume change, thermal—the increase or decrease in volume caused by changes in temperature. (See also thermal contraction and thermal expansion.)