Concrete Terminology » D
damage, abrasion—wearing away of a surface by rubbing and friction. (See also damage, cavitation and erosion.)
damage, cavitation—pitting of concrete caused by implosion, that is, the collapse of vapor bubbles in flowing water which form in areas of low pressure and collapse as they enter areas of higher pressure. (See also damage, abrasion, and erosion.)
damp—either partial saturation or moderate covering of moisture; implies less moisture than a “wet” condition and slightly more moisture than a “moist” condition.
dampproofing—treatment of concrete or mortar 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 or treated cement, or by use of a pre-formed film such as polyethylene sheets placed on grade before placing a slab. (See also vapor barrier.)
darby—a hand-manipulated straightedge, usually 3 to 8 ft (1 to 2.5 m) long, used in the early stage leveling operations of concrete or plaster, preceding supplemental floating and finishing.
dash-bond coat—see coat, dash-bond.
day—for concrete, a time period of 24 consecutive hours.
D-cracks—a series of cracks in concrete near and roughly parallel to joints, edges, and structural cracks.
dead load—see load, dead.
deadman—an anchor for a guy line, usually a beam, block, or other heavy item buried in the ground, to which a line is attached.
debonding—procedures whereby specific tendons in pretensioned construction are prevented from becoming bonded to the concrete for a predetermined distance from the ends of flexural members.
decenter—to lower or remove centering or shoring.
deck—the form on which concrete for a slab is placed, also the floor or roof slab itself. (See also deck, bridge.)
deck, bridge —the structural concrete slab or other structure that is supported on the bridge superstructure and serves as the roadway or other traveled surface.
decking—sheathing material for a deck or slab form.
deflected tendons—see tendons, deflected.
deflection—movement of a point on a structure or structural element, usually measured as a linear displacement transverse to a reference line or axis.
deflection, dowel—deflection caused by the transverse load imposed on a dowel.
deformation—a change in shape or size. (See also contraction; expansion; creep; length change; volume change; shrinkage; deformation, inelastic; and deformation, time-dependent.)
deformation, anchorage—the loss of elongation or stress in the tendons of prestressed concrete due to the deformation or seating of the anchorage when the prestressing force is transferred from the jack to the anchorage; known also as anchorage loss.
deformation, elastic—elastic deformation proportional to the applied stress. (See also deformation.)
deformation, inelastic—nonelastic deformation not proportional to the applied stress. (See also deformation; creep; deformation, time-dependent.)
deformation, nonreversible—see creep, nonrecoverable.
deformation, residual—see creep, nonrecoverable.
deformation, time-dependent—deformation caused by time-dependent factors such as autogenous volume change, thermal contraction or expansion, creep, shrinkage, and swelling.
deformed bar—see bar, deformed.
deformed plate—see plate, deformed.
deformed reinforcement—see reinforcement, deformed.
deformed tie bar—see bar, tie.
degradation—a detrimental change in the physical and/or chemical properties of a material.
degree-hour—a measure of strength gain of concrete as a function of the product of temperature multiplied by time for a specific interval. (See also factor, maturity.)
dehydration—removal of chemically bound, adsorbed, or absorbed water from a material.
deicer—a chemical, such as sodium or calcium chloride, used to melt ice or snow on slabs and pavements, such melting being due to depression of the freezing point.
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; found most frequently in bridge decks and caused by the corrosion of reinforcing steel or freezing and thawing; similar to spalling, scaling, or peeling except that delamination affects large areas and can often only be detected by nondestructive tests, such as tapping or chain dragging.
delay—see period, presteaming.
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.
demold—to remove molds from concrete test specimens or precast products. (See also strip.)
dense concrete—see concrete, dense.
dense-graded aggregate—see aggregate, dense-graded.
density—mass per unit volume (preferred over deprecated term unit weight.)
density, bulk—the mass of a material (including solid particles and any contained water) per unit volume including impermeable and permeable voids in the material. (See also specific gravity, absolute.)
density, dry—the mass per unit volume of a dry substance at a stated temperature. (See also specific gravity, absolute.)
density, dry-rodded—mass per unit volume of dry aggregate compacted by rodding under standardized conditions; used in measuring density of aggregate.
density, fired—the density of refractory concrete, upon cooling, after having been exposed to a specified firing temperature for a specified time.
density control—control of density of concrete in field construction to ensure that specified values as determined by standard tests are obtained.
depth, effective—depth of a beam or slab section measured from the compression face to the centroid of the tensile reinforcement.
design, elastic—a method of analysis in which the design of a member is based on a linear stress-strain relationship and corresponding limiting elastic properties of the material.
design, probabilistic—method of design of structures using the principles of statistics (probability) as a basis for evaluation of structural safety.
design, working-stress—a method of proportioning either structures or members for prescribed service loads at stresses well below the ultimate, and assuming linear distribution of flexural stresses and strains. (See also design, elastic.)
design criteria––Code, Standards, loads, displacement limits, materials, connections, details, and protections used in the design of mandated and voluntary work.
design load—see load, design.
design strength—see strength, design.
detensioning—process for controlled release of forces in an unbonded post-tensioned tendon.
deterioration—(1) physical manifestation of failure of a material (e.g., cracking, delamination, flaking, pitting, scaling, spalling, staining) caused by environmental or internal autogenous influences on rock and hardened concrete as well as other materials; or (2) decomposition of material during either testing or exposure to service. (See also disintegration and weathering.)
detritus—loose material produced by the disintegration of rocks through geological agencies or processes simulating those of nature.
development bond stress—see bond stress, anchorage.
development length—see length, development.
device, anchorage—see anchorage (preferred term).
device, extension—any device, other than an adjustment screw, used to obtain vertical adjustment of shoring towers.
devil’s float—see float, devil’s.
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 cracking—see cracking, diagonal.
diagonal tension—see tension, diagonal.
diametral compression test—see splitting tensile test.
diamond mesh—see mesh, diamond.
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.
diatomaceous earth—a friable earthy material composed primarily of nearly pure hydrous amorphous silica (opal) in the form of frustules of the microscopic plants called diatoms.
differential settlement—a relative variation in rate and/or magnitude of settlement in different areas of a structure.
differential thermal analysis (DTA)—indication of thermal reaction by differential thermocouple recording of temperature changes in a sample under investigation compared with those of a thermally passive control sample, that are heated uniformly and simultaneously.
diffusivity, thermal—thermal conductivity divided by the product of specific heat and density; an index of the facility with which a material undergoes temperature change.
dilation—an expansion of concrete during cooling or freezing generally calculated as the maximum deviation from the normal thermal contraction predicted from the length change-temperature curve or length change-time curve established at temperatures before initial freezing.
diluent—a substance, liquid or solid, mixed with the active constituents of a formulation to increase the bulk or lower the concentration.
dimensional compatibility—see compatibility, dimensional.
direct dumping—discharge of concrete directly into place from crane bucket or mixer.
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—two-component devices that contain parallel or concentric dispensing cartridges; plungers for each cartridge are depressed simultaneously to extrude the adhesive components in the proper proportions, usually through a static mixing tube.
dispersant—a material that deflocculates or disperses finely ground materials by satisfying the surface energy requirements of the particles; used as a slurry thinner or grinding aid.
dispersing agent—a material capable of increasing the fluidity of pastes, mortars, or concretes by reduction of inter-particle attraction.
displacement grouting—see grouting, displacement.
distress—physical manifestation of cracking and distortion in a structure as the result of stress, chemical action, or both.
distribution-bar reinforcement—see reinforcement, distribution-bar.
divider strips—see strips, divider.
documents, contract—documents comprising aspects of the required work and the results and products thereof, including plans, specifications, and project drawings.
dolomite—a mineral having a specific crystal structure and consisting of calcium carbonate and magnesium carbonate in equivalent chemical amounts which are 54.27 and 45.73% by mass, respectively; a rock containing dolomite as the principal constituent.
dolomite, hard-burned—the product of heating dolomitic rock at temperatures high enough to change the magnesium carbonate to magnesium oxide, a constituent that slowly expands on reaction with water.
dome—square prefabricated pan form used in two-way (waffle) concrete joist floor construction.
dormant crack—see crack, dormant.
double-headed nail—a nail with two heads at, or near, one end to permit easy removal; widely used in concrete formwork.
double-tee beam—see beam, double-tee.
double-up—a method of plastering characterized by application in successive operations with no setting or drying time between coats.
doughnut (donut)—a large washer of any shape for increasing bearing area of bolts and ties; also a round concrete spacer with a hole in the center to hold bars the desired distance from the forms.
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.
dowel-bar reinforcement—see dowel.
dowel deflection—see deflection, dowel.
dowel lubricant—see lubricant, dowel.
dowel rod—see rod, dowel.
drainage—the interception and removal of water from, on, or under an area or roadway; the process of removing surplus ground water or surface water artificially; a general term for gravity flow of liquids in conduits.
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 fill— (1) base course of granular material placed between floor slab and sub-grade to impede capillary rise of moisture; or (2) lightweight concrete placed on floors or roofs to promote drainage.
drainage gallery—an opening or passageway within a concrete structure from which grout holes or drainage holes are drilled. (See also grout gallery.)
dried strength—see strength, dried.
drier—chemical that promotes oxidation or drying of a paint or adhesive.
drilled-in port—pipe nipple for grout hose connection which is embedded in a short entry hole drilled into the concrete surface.
drip—a transverse groove in the underside of a projecting piece of wood, stone, or concrete to prevent water from flowing back to a wall.
dropchute—a device used to confine or to direct the flow of a falling stream of fresh concrete. (1) dropchute, articulated—a device consisting of a succession of tapered metal cylinders so designed that the lower end of each cylinder fits into the upper end of the one below; or (2) dropchute, flexible—a device consisting of a heavy rubberized canvas or plastic collapsible tube.
drop panel—see panel, drop.
drop-panel form—see form, drop-panel.
dry-batch weight—see weight, dry-batch.
dry-cast process—see process, dry-cast.
dry mix—see mix, dry.
dry-mix concrete—see concrete, dry mix.
dry-mix shotcrete—see shotcrete, dry-mix.
dry pack—see pack, dry.
dry packing—see packing, dry.
dry-rodded density—see density, dry-rodded.
dry-rodded volume—see volume, dry-rodded.
dry-rodded weight—deprecated term; see density, dryrodded.
dry rodding—see rodding, dry.
dry-shake—a dry mixture of hydraulic cement and fine aggregate (either natural or special metallic) that is distributed evenly over the surface of concrete flatwork and worked into the surface before time of final setting and then floated and troweled to desired finish; the mixture either may or may not contain pigment.
dry-tamp process—see packing, dry (preferred term).
dry topping—see dry-shake (preferred term).
dry-volume measurement—measurement of the ingredients of grout, mortar, or concrete by their bulk volume.
drying creep—see creep, drying.
drying shrinkage—see shrinkage, drying.
duct—a hole formed in a concrete member to accommodate a tendon for post-tensioning; a pipe or runway for electric, telephone, or other utilities.
ductility—that property of a material by virtue of which it may undergo large permanent deformation without rupture.
dummy joint—see joint, construction and joint, groove.
Dunagan analysis—a method of separating the ingredients of freshly mixed concrete or mortar to determine the proportions of the mixture.
durability—the ability of concrete to resist weathering action, chemical attack, abrasion, and other conditions of service.
durability factor—see factor, durability.
dust of fracture (in aggregate)—rock dust created during production processing or handling.
dusting—the development of a powdered material at the surface of hardened concrete.
dust of fracture (in aggregate)—rock dust created during production processing or handling.
dye tracer—an additive whose primary purpose is to change the color of grout or water.
dynamic analysis—see analysis, dynamic.
dynamic load—see load, dynamic.
dynamic loading—see loading, dynamic.
dynamic modulus of elasticity—see modulus of elasticity, dynamic.