— 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 wetness than that connoted by “wet” and slightly wetter than that connoted by “moist.”  (See also moist and wet.)

 

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.

 

davit — a device used to support and swing the access covers away from  openings of vessels and tanks. History

 

D-cracks — a series of cracks in concrete near and roughly parallel to joints and edges. History

 

dead end — in the stressing of a tendon from one end only, the end opposite that to which the load is applied.

 

dead-end anchorage — see anchorage, dead-end.

 

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 —

 

(1) preventing bond of prestressing tendons to surrounding concrete; or

 

 (2) failure of cohesive or adhesive bond at the interface between a substrate and a strengthening or repair system. History

 

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 road way 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 or as succession displacements transverse to a reference line or axis.

 

deflection, dowel — deflection caused by the transverse load imposed on a dowel.

 

deformation — a change in dimension or shape.  (See also contraction; expansion; creep; length change; volume change; shrinkage; deformation, inelastic; deformation, time-dependent.) History

 

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 — non-elastic 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 resulting from effects such as autogenous volume change, thermal contraction or expansion, creep, shrinkage, and swelling, each of which is a function of time.

 

deformed bar — see bar, deformed.

 

deformed plate — see plate, deformed.

 

deformed reinforcement — see reinforcement, deformed.

 

deformed tie bar — see bar, tie.

 

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 planar separation in a material that is roughly parallel to the surface of the material. History

 

delay — see period, presteaming.

 

delayed ettringite formation — a form of sulfate attack by which mature hardened concrete is damaged by internal expansion during exposure to cyclic wetting and drying in service and caused by the late formation of ettringite; not because of excessive sulfate; not likely to occur unless the concrete has been exposed to temperatures during curing of 160 ºF (70 ºC) or greater; and less likely to occur in concrete made with pozzolan or slag cement. (See also ettringite.)

 

delivery hose — see hose, delivery.

 

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-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.

 

density (dry) — the mass per unit volume of a dry substance at a stated temperature.   (See also specific gravity, absolute.)

 

depth, effective — depth of a beam or slab section measured from the compression face to the centroid of the tensile reinforcement.

 

design —

 

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 load — see load, design.

 

design strength — see strength, design.

 

detail, emulative — a connection in which the structural performance is equivalent to that of a continuous member or a monolithic connection. History

 

detail, jointed — a connection where the bending stiffness differs from that of the members and requires special design to collect, transfer, and redistribute forces from one member to another through the connection. History

 

deterioration —

 

(1) physical manifestation of failure of a material (for example, 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.)

 

development bond stress — see stress, anchorage bond.

 

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.

 

diagonal crack — see crack, diagonal.

 

diagonal cracking — see cracking, diagonal.

 

diagonal tension — see tension, diagonal.

 

diameter, equivalent fiber — diameter of a circle having an area equal to the average cross-sectional area of a fiber. History

 

diametral compression test — see splitting tensile test.

 

diamond mesh — see mesh, diamond.

 

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.

 

dicalcium silicate — a compound having the composition 2CaO·SiO₂, abbreviated C₂S, an impure form of which (belite) occurs in portland-cement clinker.  (See also belite.)

 

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.

 

direct dumping — discharge of concrete directly into place from crane bucket or mixer.

 

discoloration — departure of color from that which is normal or desired.

 

disintegration — reduction into small fragments and subsequently into particles. (See also deterioration and weathering.)

 

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.

 

dispersant agent — an agent capable of increasing the fluidity of pastes, mortars, or concretes by reduction of inter-particle attraction.

 

distortion — see deformation.

 

distress — physical manifestation of cracking and distortion in a concrete structure as the result of stress, chemical action, or both.

 

distribution-bar reinforcement — see reinforcement, distribution-bar.

 

divider strips — see strips, divider.

 

D-line cracks — see D-cracks (preferred term).

 

documents, contract — a set of documents supplied by the owner to the contractor as the basis for construction. These documents contain contract forms, contract conditions, specifications, drawings, addenda, and contract changes. History

 

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.

 

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 to increase bearing area of bolts and ties; also a round concrete spacer with hole in the center to hold bars the desired distance from the forms.

 

dowel —

 

(1) a steel pin, commonly a plain or coated round steel bar that extends into adjoining portions of a concrete construction, as at an expansion or contraction joint in a pavement slab, so as to transfer shear loads; or

 

(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 fill —

 

(1) base course of granular material placed between floor slab and sub-grade to impede capillary rise of moisture; or

 

(2) also, lightweight concrete placed on floors or roofs to promote drainage.

 

draped tendons — see tendons, deflected (preferred term).

 

dried strength — see strength, dried.

 

drier — chemical that promotes oxidation or drying of a paint or adhesive.

 

drilled pier — see pier, drilled.

 

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-in beam — see beam, drop-in.

 

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 shotcrete — see shotcrete, dry-mix.

 

dry mixing — see mixing, dry.

 

dry pack — see pack, dry.

 

dry-packed concrete — see concrete, dry-packed.

 

dry packing — see packing, dry.

 

dry process — see process, dry.

 

dry-rodded density — see density, dry-rodded.

 

dry-rodded volume — see volume, dry-rodded.

 

dry-rodded weight — deprecated term; see density, dry-rodded.

 

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 a material to resist weathering action, chemical attack, abrasion, and other conditions of service. History

 

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.

 

dye, fugitive — see fugitive dye.

 

dynamic analysis — see analysis, dynamic.

 

dynamic load — see load, dynamic.

 

dynamic loading — see loading, dynamic.

 

dynamic modulus of elasticity — see modulus of elasticity, dynamic.