Concrete Terminology » S

sack—see bag (of cement) (preferred term).

sack rub—a finish for formed concrete surfaces, designed to produce even texture and fill pits and air holes; after dampening the surface, mortar is rubbed over the surface, then, before the surface dries, a mixture of dry cement and sand is rubbed over it with either a wad of burlap or a sponge-rubber float to remove surplus mortar and fill voids. (See also surface air voids and finish, rubbed.)

sacrificial anode—see anode, sacrificial.

safe leg load—see load, safe leg.

sagging—nonuniform downward flow of a material that occurs between the time of application and setting. (See also sloughing).

salamander—a portable source of heat, customarily oilburning, used to heat an enclosure around or over newly placed concrete to prevent the concrete from freezing.

sample—either a group of units or portion of material taken, respectively, from a larger collection of units or a larger quantity of material, that serves to provide information that can be used as a basis for action on the larger collection or quantity or on the production process; the term is also used in the sense of a sample of observations.

sample, composite—sample obtained by blending two or more individual samples of a material.

sampling—identifying and testing or removing materials or components from a structure for the purpose of conducting laboratory tests to determine material or structural properties or to further quantify physical condition.

sampling, continuous—sampling without interruptions throughout an operation or for a predetermined time.

sampling, intermittent—sampling successively for limited periods of time throughout an operation or for a predetermined period of time; the duration of sampling periods and the intervals are not necessarily regular and are not specified.

sampling plan— (1) a procedure that specifies the number of units of product from a lot that is to be inspected to establish acceptability of the lot; and (2) a prearranged program stipulating locations and procedures for securing samples of a material for testing purposes, for example, as concrete in construction or aggregates in a quarry, pit, or stockpile.

sand, graded standard—see sand, standard.

sand, manufactured—see sand.

sand, natural—sand resulting from natural disintegration and abrasion of rock. (See also sand and aggregate, fine.)

sand, sharp—coarse sand consisting of particles of angular shape.

sand, standard—silica sand, composed almost entirely of naturally rounded grains of nearly pure quartz, used for preparing mortars in the testing of hydraulic cements.

sand, stone—fine aggregate resulting from the mechanical crushing and processing of rock. (See also aggregate, fine and sand.)

sandblasting—a method of cutting or abrading a surface with a stream of sand ejected from a nozzle at high speed by compressed air; often used for cleanup of horizontal construction joints or for exposure of aggregate in architectural concrete. (See also abrasive blasting.)

sand box (or sand jack)—a tight box filled with clean, dry, sand on which rests a tight-fitting timber plunger that supports the bottom of posts used in centering; removal of a plug from a hole near the bottom of the box permits the sand to run out when it is necessary to lower the centering.

sand equivalent—a measure of the relative proportions of detrimental fine dust, claylike material or both in soils or fine aggregate.

sand jack—see sand box.

sand plate—a flat steel plate or strip welded to the legs of bar supports for use on compacted soil.

sand pocket—a zone in concrete, mortar, or shotcrete containing fine aggregate with little or no cement.

sand streak—a streak of exposed fine aggregate in the surface formed concrete, caused by bleeding.

sand-coarse aggregate ratio—ratio of fine-to-coarse aggregate in a batch of concrete, by mass or by volume.

sand-lightweight concrete—see concrete, sand-lightweight.

sand-lime brick—see brick, calcium-silicate (preferred term).

sanded grout—see grout, sanded.

sandstone—a cemented or otherwise indurated sedimentary rock composed predominantly of sand grains.

sandwich panel—see panel, sandwich.

Santorin earth—a volcanic tuff originating on the Grecian island of Santorin and used as a pozzolan.

saponification—the alkaline hydrolysis of fats forming a soap; more generally, the hydrolysis of an ester by an alkali with the formation of an alcohol and a salt of the acid portion.

saturated surface-dry—condition of an aggregate particle or other porous solid when the permeable voids are filled with water and no water is on the exposed surfaces.

saturated surface-dry (SSD) particle density—the mass of the saturated surface-dry aggregate divided by its displacement volume in water or in concrete.

saturation—(1) in general: the condition of coexistence in stable equilibrium of either a vapor and a liquid or a vapor and solid phase of the same substance at the same temperature; and (2) as applied to aggregate or concrete: the condition such that no more liquid can be held or placed within it.

saturation, critical—a condition describing the degree of filling by freezable water of a pore space in cement paste or aggregate that affects the response of the material to freezing; usually taken to be 91.7% because of the 9% increase in volume of water undergoing the change of state to ice.

saturation, vacuum—a process for increasing the amount of filling of the pores in a porous material, such as lightweight aggregate, with a fluid, such as water, by subjecting the porous material to reduced pressure while immersed in the fluid.

saw cut—a cut in hardened concrete made by abrasive blades, discs, or diamond wires.

sawdust concrete—see concrete, sawdust.

sawed joint—see joint, sawed.

scab—a short piece of wood fastened to two formwork members to secure a butt joint.

scabbler—equipment for removal of concrete and coatings by chipping with piston-driven cutting heads placed at a right angle to the surface.

scaffolding—a temporary structure for the support of deck forms, cartways, or workers, or a combination of these, such as an elevated platform for supporting workers, tools, and materials; adjustable metal scaffolding is frequently adapted for shoring in concrete work.

scaling—local flaking or peeling away of the near-surface portion of hardened concrete or mortar; also of a layer from metal. (See also peeling, and spalling.)

Note: light scaling of concrete does not expose coarse aggregate; medium scaling involves loss of surface mortar to 5 to 10 mm in depth and exposure of coarse aggregate; severe scaling involves loss of surface mortar to 5 to 10 mm in depth with some loss of mortar surrounding aggregate particles 10 to 20 mm in depth; very severe scaling involves loss of coarse aggregate particles as well as mortar generally to a depth greater than 20 mm.

scalper—a sieve for removing oversize particles.

scalping—the removal, by sieving, of particles larger than a specified size.

scanning electron microscope (SEM)—see microscope, scanning electron (SEM).

scarf connection—see connection, scarf.

scarf joint—see scarf connection (preferred term).

scarifier—milling equipment for removal of concrete or brittle coatings by fracturing and pulverizing with rotary impact cutters held at a right angle to the surface.

scarification—the process of scratching, cutting, or chipping a substrate to clean and texture the surface.

schist—a finely layered metamorphic rock that splits easily and in which the grain is coarse enough to permit identification of the principal minerals.

Schmidt hammer—see hammer, rebound.

scoria—vesicular volcanic ejecta of larger size, usually of basic composition and characterized by dark color; the material is relatively heavy and partly glassy, partly crystalline; the vesicles do not generally interconnect. (See also aggregate, lightweight.)

scour—erosion of a concrete surface, exposing the aggregate.

scratch coat—see coat, scratch.

screed—(1) to strike off concrete lying above the desired plane or shape. (2) a tool for striking off the concrete surface, sometimes referred to as a strikeoff.

screed, cutting—sharp-edged tool used to trim shotcrete to the finished outline. (See also rod.)

screed guide—firmly established grade strips or side forms for unformed concrete that guide the strikeoff in producing the desired plane or shape.

screed rails—see screed guide.

screed wire—see wire, ground.

screeding—the operation of forming a surface by the use of screed guides and a strikeoff. (See also strikeoff.

screen—production equipment for separating granular material according to size, using woven-wire cloth or other similar device with regularly spaced apertures of uniform size.

screens, finish—vibrating screens (preferably horizontal) operated at a batching plant so that excessive amounts of significant undersize material are removed and delivered directly to the appropriate batcher bin without intermediate storage.

screw, adjustment—a leveling device or jack composed of a threaded screw and an adjusting handle; used for the vertical adjustment of shoring and formwork.

seal—a barrier against the passage of liquids, solids, or gases.

sealant—a material that has adhesive and cohesive properties to form a seal.

sealant, field-molded—a liquid or mastic sealant that is shaped by the joint into which it is placed.

sealant, joint—compressible material used to exclude water and solid foreign materials from joints.

sealant, structural—a sealant capable of transferring required loads between adjacent structural elements.

sealer—a liquid that is applied to the surface of hardened concrete to either prevent or decrease the penetration of liquid or gaseous media, for example water, aggressive solutions, and carbon dioxide, during service exposer, that is absorbed by the concrete, is colorless, and leaves little or nothing visible on the surface. (See also coating and compound, curing.)

sealing compound—see sealer.

seating—see deformation, anchorage.

secant modulus—see modulus of elasticity.

secondary crusher—see crusher, secondary.

secondary moment—see moment, secondary.

secondary nuclear vessel—exterior container or safety container in a nuclear reactor subjected to design load only once in its lifetime, if at all.

section, transformed—a hypothetical section of one material arranged so as to have the same elastic properties as a section of two or more materials.

section enlargement—see strengthening, section enlargement.

section modulus—see modulus, section.

seepage—the infiltration or percolation of water through a material to or from the surface.

segmental member—see member, segmental.

segregation—the differential concentration of the components of mixed concrete, aggregate, or the like, resulting in nonuniform proportions in the mass. (See also bleeding and separation.)

seismometer—instrument to detect linear (vertical, horizontal) or rotational displacement, velocity, or acceleration.

self-desiccation—the removal of free water by chemical reaction so as to leave insufficient water to cover the solid surfaces and cause a decrease in the relative humidity of the system; applied to an effect occurring in sealed concretes, mortars, and pastes.

self-furring—metal lath or welded-wire fabric formed in the manufacturing process to include means by which the material is held away from the supporting surface, thus creating a space for “keying” of the insulating concrete, plaster, or stucco.

self-furring nail—nails with flat heads and a washer or a spacer on the shank; for fastening reinforcing wire mesh and spacing it from the nailing member.

self-leveling—the process whereby a material exhibits flow sufficient to seek gravitational leveling.

self-stressing cement—see cement, expansive.

self-stressing concrete (mortar or grout)—see concrete (mortar or grout), self-stressing.

selvage—a finished edge of woven-wire screen cloth produced in the weaving process of the finer meshes.

semiautomatic batcher—see batcher.

semiflexible joint—see joint, semiflexible.

sensor—a device designed to respond to a physical stimulus (as temperature, illumination, and motion) and transmit a resulting signal for interpretation, measurement, or for operating a control.

separation—the tendency, as concrete is caused to pass from the unconfined ends of chutes or conveyor belts or similar arrangements, for coarse aggregate to separate from the concrete and accumulate at one side; the tendency, as processed aggregate leaves the ends of conveyor belts, chutes, or similar devices with confining sides, for the larger aggregate to separate from the mass and accumulate at one side; or the tendency for the solids to separate from the water by gravitational settlement. (See also bleeding and segregation.)

separation, heavy-media—a method in which a liquid or suspension of given specific gravity is used to separate particles into a portion lighter than (those that float) and a portion heavier than (those that sink) the medium.

separation joint—see joint, isolation (preferred term).

separator, air—an apparatus that separates various size fractions of ground materials pneumatically; fine particles are discharged as product; oversized are returned to the mill as tailing.

sequence-stressing loss—in post-tensioning, the elastic loss in a stressed tendon resulting from the shortening of the member when additional tendons are stressed.

series grouting—see grouting, series.

service condition—the combination of load and environmental exposure that a structure or material may be subjected to during its design life.

service dead load—see load, service dead.

service life—an estimate of the remaining useful life of a structure based on the current rate of deterioration or distress, assuming continued exposure to given service conditions without repairs.

service live load—see load, service live.

service load— see load, service.

set (n.)—the condition reached by a cement paste, mortar, or concrete when it has lost plasticity to an arbitrary degree, usually measured in terms of resistance to penetration or deformation; initial set refers to first stiffening; final set refers to attainment of significant rigidity; also, strain remaining after removal of stress. (See also set, permanent.)

set, false—the rapid development of rigidity in a freshly mixed portland cement paste, mortar, or concrete without the evolution of much heat, which rigidity can be dispelled and plasticity regained by further mixing without addition of water. (See also set, flash.)

set, final—a degree of stiffening of a mixture of cement and water greater than initial set, generally stated as an empirical value indicating the time in hours and minutes required for a cement paste to stiffen sufficiently to resist, to an established degree, the penetration of a weighted test needle; also applicable to concrete and mortar mixtures with use of suitable test procedures. (See also set, initial.)

set, flash—the rapid development of rigidity in a freshly mixed portland cement paste, mortar, or concrete, characteristically with the evolution of considerable heat, which rigidity cannot be dispelled nor can the plasticity be regained by further mixing without addition of water; also referred to as quick set or grab set. (See also set, false.)

set, grab—see set, flash (preferred term).

set, hesitation—see set, false (preferred term).

set, initial—a degree of stiffening of a mixture of cement and water less than final set, generally stated as an empirical value indicating the time in hours and minutes required for cement paste to stiffen sufficiently to resist to an established degree, the penetration of a weighted test needle; also applicable to concrete or mortar with use of suitable test procedures. (See also set, final.)

set, pack—see cement, sticky and set, warehouse.

set, permanent—inelastic elongation or shortening.

set, rubber—see set, false (preferred term).

set, stockhouse—see cement, sticky and set, warehouse.

set, warehouse—(1) the partial hydration of cement stored for a time and exposed to atmospheric moisture; and (2) mechanical compaction occurring during storage. (See also cement, sticky.)

set-accelerating admixture—see accelerator.

set-control addition—material, composed essentially of calcium sulfate in any hydration state from CaSO4 to CaSO4.2H2O, interground with the clinker during manufacture of cement to modify the setting time of the cement.

set-retarding admixture—see admixture, retarding and retarder.

setting time—time of setting (preferred term).

setting time, final—the time required for a freshly mixed cement paste, mortar, or concrete to achieve final set. (See also time, initial setting.)

setting time, initial—the time required for a freshly mixed cement paste, mortar, or concrete to achieve initial set. (See also time, final setting.)

settlement—(1) downward movement of a structure, part of a structure, or underpinning. (2) sinking of solid particles in grout, mortar, or fresh concrete, after placement and before initial set. (See also bleeding).

settlement shrinkage—see shrinkage, settlement.

settling—the lowering in elevation of sections of pavement or structures due to their mass, the loads imposed on them, or shrinkage or displacement of the support.

settling velocity—see velocity, settling.

shale—a laminated and fissile sedimentary rock, the constituent particles of which are principally in clay and silt sizes; the laminations are bedding planes of the rock.

shale, expanded (clay or slate)—lightweight vesicular aggregate obtained by firing suitable raw materials in a kiln or on a sintering grate under controlled conditions.

sharp sand—see sand, sharp.

she bolt—see bolt, she.

shear—an internal force tangential to the plane on which it acts.

shear collar—enlarged column section immediately below a slab that aids in transfer of shear stresses from the slab into the supporting column.

shear modulus—see modulus of rigidity.

shear reinforcement—see reinforcement, shear.

shear strength—see strength, shear.

shear stress—the stress component acting tangentially to a plane.

shear—an internal force tangential to the plane on which it acts.

shear-bond strength—see strength, shear bond.

shearhead—assembled unit in the top of the columns of flat slab or flat plate construction for transmitting loads from slab to column.

shearwall—a wall portion of a structural frame intended to resist lateral forces, such as earthquake, wind, and blast, acting in the plane of the wall.

sheath—enclosure around prestressing steel to avoid temporary or permanent bond between the steel and surrounding concrete. (See also duct.)

sheathing—the material forming the contact face of forms; also called lagging or sheeting.

sheet pile—see pile, sheet.

sheeting—see sheathing (preferred term).

shelf angles—structural angles with holes or slots in one leg for bolting to the structure to support brick work, stone, or terra cotta.

shelf life—the length of time packaged materials can be stored under specified conditions and still remain usable.

shell construction—see construction, shell.

shelly structure—see perlitic structure (preferred term).

shielding concrete—see concrete, shielding.

shim—a strip of metal, wood, or other material employed to set base plates or structural members at the proper level for placement of grout, or to maintain the elongation in some types of post-tensioning anchorages.

shiplap—a type of joint in lumber or precast concrete made by using pieces having a portion of the width cut away on both edges, but on opposite sides, so as to make a flush joint with similar pieces.

shock, thermal—the subjection of newly hardened concrete to a rapid change in temperature that may be expected to have a potentially deleterious effect.

shock load—see load, shock.

shooting—placing of shotcrete. (See also gunning.)

shoot wire—a wire running across the width of the sieve cloth, as woven; also known as fill, filler, weft, or woof wire.

shore—a temporary support for formwork and fresh concrete or for recently built structures that have not developed full design strength; also called prop, tom, post, and strut. (See also L-head and T-head.)

shore, pole—see shore, post.

shore, post—individual vertical member used to support loads; also known as pole shore. (1) adjustable timber single-post shore—individual timber used with a fabricated clamp to obtain adjustment; not normally manufactured as a complete unit; (2) fabricated single-post shore: Type I—single all-metal post with a fine-adjustment screw or device in combination with pin-and-hole adjustment or clamp; Type II: single or double wooden post members adjustable by a metal clamp or screw and usually manufactured as a complete unit; and (3) timber single-post shore—timber used as a structural member for shoring support.

shore head—wood or metal horizontal member placed on and fastened to a vertical shoring member. (See also raker.)

shoring––props or posts of timber or other material in compression used for the temporary support of excavations, formwork, or unsafe structures; the process of erecting shores.

shoring, horizontal—metal or wood load-carrying strut, beam, or trussed section used to carry a shoring load from one bearing point, column, frame, post, or wall to another; may be adjustable.

shoring layout—a drawing prepared before erection showing arrangements of equipment for shoring.

short column—see column, short.

shorten—to decrease in length. (See also contraction; elongation; and shrinkage.)

shortening, elastic—in prestressed concrete, the shortening of a member that occurs immediately on the application of forces induced by prestressing.

shorten—to decrease in length. (See also contraction; elongation; and shrinkage.)

short-pulse radar—a technique for nondestructive detection of delaminations and other types of defects within a concrete mass.

shotblasting—surface preparation method in which steel shot is centrifugally propelled at high velocity onto a surface; the process is confined in an enclosed blast chamber which recovers and separates dust and reusable shot.

shotcrete—mortar or concrete pneumatically projected at high velocity onto a surface; also known as air-blown mortar, pneumatically applied mortar or concrete, and sprayed concrete. (See also feed, pneumatic; positive displacement; shotcrete, dry-mix; and shotcrete, wet-mix.)

shotcrete, dry-mix—shotcrete in which most of the mixing water is added at the nozzle.

shotcrete, wet-mix—shotcrete in which the ingredients, including water, are mixed before introduction into the delivery hose; accelerator, if used, is normally added at the nozzle.

shoulder—an unintentional offset in a formed concrete surface usually caused by bulging or movement of formwork.

shrink-mixed concrete—see concrete, shrink-mixed.

shrinkage—a decrease in one or more dimensions of an object or material. (See also contraction and volume change.)

shrinkage, carbonation—shrinkage caused by carbonation.

shrinkage, drying—shrinkage resulting from loss of moisture.

shrinkage, initial drying—the difference between the length of a specimen (molded and cured under stated conditions) and its length when first dried to constant length, expressed as a percentage of the moist length.

shrinkage, plastic—shrinkage that occurs prior to setting of a cementitious material.

shrinkage, settlement—a reduction in volume of concrete prior to the final set of cementitious mixtures, caused by settling of the solids. (See also shrinkage, plastic and volume change, autogenous.)

shrinkage-compensating—a characteristic of grout, mortar, or concrete made using an expansive cement in which volume increases after setting, if properly elastically restrained, induces compressive stresses which are intended to approximately offset the tendency of drying shrinkage to induce tensile stresses. (See also cement, expansive.)

shrinkage-compensating cement—see cement, expansive.

shrinkage-compensating concrete—see concrete, shrinkage-compensating.

shrinkage crack—see crack, shrinkage.

shrinkage cracking—see cracking, shrinkage.

shrinkage limit—see limit, shrinkage.

shrinkage loss—see loss, shrinkage.

shrinkage-reducing admixture—see admixture, shrinkage-reducing.

shuttering—see formwork.

SI (Système International)—the modern metric system. (See ASTM E 380.)

side, pilaster—the form for the side surface of a pilaster perpendicular to the wall.

sieve—a metallic plate or sheet, a woven-wire cloth, or other similar device with regularly spaced apertures of uniform size, mounted in a suitable frame or holder for use in separating granular material according to size.

sieve analysis—see analysis, sieve.

sieve correction—correction of a sieve analysis to adjust for deviation of sieve performance from that of standard calibrated sieves.

sieve fraction—that portion of a sample that passes through a standard sieve of specified size and is retained by some finer sieve of specified size.

sieve number—a number used to designate the size of a sieve, usually the approximate number of openings per linear inch; applied to sieves with openings smaller than 6.3 mm (1/4 in.). (See also mesh.)

sieve size—nominal size of openings between cross wires of a testing sieve.

significant (statistically significant)—values of a test statistic that lie outside of predetermined limits of test precision and so taken to indicate a difference between populations.

silane—a low-molecular-weight compound of silicon and hydrogen, solutions of which are used as penetrating sealers for concrete surfaces.

silica—silicon dioxide (SiO2).

silica flour—very finely divided silica, a siliceous binder component that reacts with lime under autoclave curing conditions; prepared by grinding silica, such as quartz, to a fine powder; also known as silica powder.

silica fume—very fine noncrystalline silica produced in electric arc furnaces as a byproduct of the production of elemental silicon or alloys containing silicon.

silica powder—see silica flour (preferred term).

silicate—salt of a silicic acid. (See alite; belite; blast-furnace slag; bredigite; celite; brick, calcium-silicate; hydrate, calcium-silicate; concrete, siliceous-aggregate;clay; dicalcium silicate; clay, fire; fluosilicate; lime, hydraulic hydrated; kaolin; larnite; melilite; smectite;Stratling’s compound; tobermorite; tricalcium silicate;vermiculite; and xonotlite.)

siliceous-aggregate concrete—see concrete, siliceous-aggregate.

silicon carbide—an artificial product (SiC), granules of which may be embedded in concrete surfaces to increase resistance to wear or as a means of reducing skidding or slipping on stair treads or pavements; also used as an abrasive in saws and drills for cutting concrete and masonry, and as abrasive grit in a range of particle sizes.

silicone—see resin, silicone.

sill—see mud sill.

siloxane—a silicon and oxygen-based compound, also containing carbon and hydrogen, used as a penetrating sealer for concrete surfaces.

simple beam—see beam, simple.

single-sized aggregate—see aggregate, single-sized.

single-stage curing—see curing, single-stage.

sinter—a ceramic material or mixture fired to less than complete fusion, resulting in a coherent mass; also the process involved.

sintering—the formation of a porous mass of material by the agglomeration of fine particles during particle fusion.

sintering grate—a grate on which material is sintered.

size, nominal—see nominal maximum size (of aggregate).

skew back—sloping surface against which the end of an arch rests, such as a concrete thrust block supporting thrust of an arch bridge. (See also strip, chamfer.)

skid resistance—see resistance, skid.

skinning—the formation of a solid membrane on the top of a liquid, caused by partial curing or drying of a coating during storage.

slab—a molded layer of plain or reinforced concrete, flat, horizontal (or nearly so), usually of uniform but sometimes of variable thickness, either on the ground or supported by beams, columns, walls, or other framework. (See also slab, flat and plate, flat.)

slab, flat—a concrete slab reinforced in two or more directions and having drop panels, column capitals or both. (See also plate, flat.)

slab, ribbed—see panel, ribbed.

slab bolster—see bolster, slab.

slab spacer—see spacer, slab.

slab strip—see strip, middle (preferred term).

slabjacking—the process of either raising concrete slabs or filling voids under them, or both, by pressure injecting a material (cementitious, noncementitious, or asphaltic) under the slabs.

slab-on-grade—a slab, continuously supported by ground, whose total loading when uniformly distributed would impart a pressure to the grade or soil that is less than 50% of the allowable bearing capacity thereof; the slab may be of uniform or variable thickness, and it may include stiffening elements such as ribs or beams; the slab may be plain, reinforced, or prestressed concrete; reinforcement or prestressing steel may be provided to accommodate the effects of shrinkage and temperature or structural loading. (Also referred to as slab-on-ground; slab-on-grade is the preferred term.)

slag—see blast-furnace slag.

slag cement—see cement, slag.

slant-shear bond strength—see strength, slant-shear bond.

slate—a fine-grained metamorphic rock possessing a well-developed fissility (slaty cleavage), usually not parallel to the bedding planes of the rock.

sleeve—a pipe or tube passing through formwork for a wall or slab through which pipe, wires, or conduit can be passed after the forms have been stripped.

sleeve, expansion—a tubular metal covering for a dowel bar to allow its free longitudinal movement at a joint.

slender beam—see beam, slender.

slender column—see column, slender.

slenderness ratio—the effective unsupported length of a uniform column divided by the least radius of gyration of the cross-sectional area.

slick line—end section of a pipeline used in placing concrete by pump which is immersed in the placed concrete and moved as the work progresses.

sliding form—see slipform (preferred term).

sling psychrometer—see psychrometer, sling.

slip—movement occurring between steel reinforcement or other embedded items and concrete, indicating degraded or ineffective anchorage.

slip, anchorage—see deformation, anchorage or slip.

slip resistance—the frictional force opposing movement of an object across its surface. (See also coefficient of friction.)

slipform—a form that is pulled or raised as concrete is placed; may move in a generally horizontal direction to lay concrete evenly for highway paving or on slopes and inverts of canals, tunnels, and siphons; or may move vertically to form walls, bins, or silos.

sloped footing—see footing, sloped.

sloughing—subsidence of shotcrete, plaster, or the like, due generally to excessive water in the mixture; also called sagging.

slugging—pulsating and intermittent flow of shotcrete material due to improper use of delivery equipment and materials.

slump—a measure of consistency of freshly mixed concrete, mortar, or stucco equal to the subsidence measured to the nearest 1/4 in. (5 mm) of the molded specimen immediately after removal of the slump cone.

slump cone—see cone, slump.

slump loss—see loss, slump.

slump test—see test, slump.

slurry—a mixture of water and any finely divided insoluble material, such as portland cement, slag, or clay in suspension.

slush grouting—see grouting, slush.

smectite—a group of clay minerals, including montmorillonite, characterized by a sheet-like internal atomic structure; consisting of extremely finely-divided hydrous aluminum or magnesium silicates that swell on wetting, shrink on drying, and are subject to ion exchange.

snap tie—a proprietary concrete wall-form tie, the end of which can be twisted or snapped off after the forms have been removed.

soaking period—see period, soaking.

sodium chloride—common salt.

soffit—the underside of an element or structure, such as a beam, staircase, arch, or cornice.

soft particle—an aggregate particle possessing less than an established degree of hardness or strength as determined by a specific testing procedure.

soil—a generic term for unconsolidated natural surface material above bedrock.

soil, fine-grained—soil in which the smaller grain sizes predominate, such as fine sand, silt, and clay.

soil, coarse-grained—soil in which the larger grain sizes, such as sand and gravel, predominate.

soil cement—a mixture of soil and measured amounts of portland cement and water, compacted to a high density.

soil pressure—see contact pressure.

soil stabilization—chemical or mechanical treatment designed to either increase or maintain the stability of a mass of soil or otherwise to improve its engineering properties.

soldier—a vertical wale used to strengthen or align formwork or excavations.

solid masonry unit—a unit whose net cross-sectional area in every plane parallel to the bearing surface is 75% or more of its gross cross-sectional area measured in the same plane.

solid masonry wall—see masonry wall, solid.

solid panel—see panel, solid.

solid volume—see volume, absolute.

solid-unit masonry—see masonry, solid-unit.

solids content—the percentage by weight of the nonvolatile matter in an adhesive.

solubility—the amount of one material that will dissolve in another, generally expressed as mass percent, as volume percent, or parts per 100 parts of solvent by mass or volume at a specified temperature.

soluble chloride—the fraction of the total chloride-ion content within hardened concrete that is available to act in the electrochemical process of reinforcing steel corrosion.

solution—a liquid consisting of at least two substances, one of which is a liquid solvent in which the other or others, that may be either solid or liquid, are dissolved.

solvent—a liquid capable of dissolving another material.

solvent entrapment—the encapsulation of solvent within a cured coating because of improper drying conditions; results in a discontinuous coating system.

sonic echo—a nondestructive testing method for determining the length of deep foundations or the location of cracks or constrictions; a hammer is used to impact the surface and a receiver monitors reflected stress wave.

sonic modulus—see modulus of elasticity, dynamic.

sounding—a technique to evaluate the condition of hardened concrete by striking the surface with a hammer; sound concrete will exhibit a clear ringing sound, whereas dull or hollow sounds indicate delaminated areas. (See also chain drag or, more broadly, acoustic impact.)

sounding well—a vertical pipe, with closely spaced openings, positioned in a mass of coarse aggregate for grout injection of preplaced aggregate concrete, a float on a measured line indicates the grout level.

soundness—the freedom of a solid from cracks, flaws, fissures, or variations from an accepted standard; in the case of a cement, freedom from excessive volume change after setting; in the case of aggregate, the ability to withstand the aggressive action to which concrete containing it might be exposed, particularly that due to weather.

space, capillary—void space in concrete resembling microscopic channels small enough to draw liquid water through them by the molecular attraction of the water adsorbed on their inner surfaces.

spacer—device that maintains reinforcement in proper position; also a device for keeping wall forms apart at a given distance before and during concreting. (See also spreader.)

spacer, slab—bar support and spacer for slab reinforcement; similar to slab bolster but without corrugations in top wire; no longer in general use. (See also bolster, slab.)

spacing factor—see factor, spacing.

spading—consolidation of mortar or concrete by repeated insertion and withdrawal of a flat, spadelike tool.

spall—a fragment, usually in the shape of a flake, detached from a larger mass by a blow, by the action of weather, by pressure, or by expansion within the larger mass; a small spall involves a roughly circular depression not greater than 120 mm in depth and 150 mm in any dimension; a large spall, may be roughly circular or oval or in some cases elongated, is more than 20 mm in depth and 150 mm in greatest dimension.

spalling—the development of spalls.

span—distance between the support reactions of members carrying transverse loads.

span, effective—the lesser of the two following distances: a) the distance between supports; or b) the clear distance between supports plus the effective depth of the beam or slab.

span-depth ratio—the numerical ratio of total span-to-member depth.

span length—see span, effective.

spandrel—that part of a wall between the head of a window and the sill of the window above it.

spandrel beam—see beam, spandrel.

spatterdash—a rich mixture of portland cement and coarse sand; it is thrown onto a background by a trowel, scoop, or other appliance so as to form a thin, coarse-textured, continuous coating; as a preliminary treatment before rendering, it assists bond of the undercoat to the background, improves resistance to rain penetration, and evens out the suction of variable backgrounds. (See also coat, dashbond and parge.)

specific gravity—the ratio of the mass of a volume of a material at a stated temperature to the mass of the same volume of distilled water at a stated temperature.

specific gravity, apparent—the ratio of the mass of a volume of the impermeable portion of a material at a stated temperature to the mass of an equal volume of distilled water at a stated temperature;

specific gravity, bulk—the ratio of the mass of a volume of a material (including the permeable and impermeable voids in the material, but not including the voids between particles of the material) at a stated temperature to the mass of an equal volume of distilled water at a stated temperature; and

specific gravity, bulk (saturated-surface-dry)—the ratio of the mass of a volume of a material (including the mass of water within the voids, but not including the voids between particles) at a stated temperature to the mass of an equal volume of distilled water at a stated temperature. (See also density.)

specific gravity factor—the ratio of the mass of aggregates (including moisture), as introduced into the mixer, to the effective volume displaced by the aggregates.

specific heat—the amount of heat required per unit mass to cause a unit rise of temperature, over a small range of temperature.

specific surface—see surface, specific.

specification (in ASTM)—an explicit set of requirements to be satisfied by a material, product, system, or service.

specification, performance-based—a specification in which the requirements are stated in terms of required results with criteria for verifying compliance rather than specific composition, design, or procedure.

specimen—a piece or portion of a sample used to make a test.

spectral analysis of surface waves (SASW)—a nondestructive test method for determining the stiffness profile of a pavement system or the depth of deteriorated concrete; impact is used to generate a surface wave and two receivers monitor the surface motion.

spectrophotometer—instrument for measuring the intensity of radiant energy of desired frequencies absorbed by atoms or molecules; substances are analyzed by converting the absorbed energy to electrical signals proportional to the intensity of radiation. (See also spectroscopy, infrared and photometer, flame.)

spectroscopy, infrared—the use of a spectrophotometer for determination of infrared absorption spectra (2.5 to 18 μm wave lengths) of materials; used for detection, determination, and identification especially of organic materials.

spectroscopy, X-ray emission—see X-ray fluorescence.

speed, agitating—the rate of rotation of the drum of a truck mixer or agitator when used for agitating mixed concrete.

spinning—the essential factor of the process of producing spun concrete. (See also concrete, spun.)

spiral reinforcement—see reinforcement, spiral.

spirally reinforced column—see column, spirally reinforced.

splice—connection of reinforcing bars or prestressing tendons to one another by lapping, welding, mechanical couplers, or other means; connection of welded-wire fabric by lapping; connection of piles by mechanical couplers.

splice, center stressing—a device that allows stressing and splicing to occur from an intermediate location along the length of a tendon. Also called a stressing coupler or colloquially a “dogbone” coupler because of its shape.

splice, contact—a means of connecting reinforcing bars in which the bars are lapped and in direct contact. (See also splice, lap.)

splice, coupler—a device for connecting reinforcing bars or prestressing tendons end to end.

splice, lap—a connection of reinforcing steel made by lapping the ends of bars.

splice, welded-butt—a reinforcing bar splice made by welding the butted ends.

splice, Y— a device that provides for tendon stressing at a splice location.

split block—see split-face block.

split-batch charging—method of charging a mixer in which the solid ingredients do not enter the mixer together; cement, and sometimes different sizes of aggregate, may be added separately.

split-face block—a concrete masonry unit with one or more faces purposely fractured to provide architectural effects in masonry wall construction.

splitting tensile strength—see strength, splitting tensile.

splitting tensile test (diametral compression test)—a test for tensile strength in which a cylindrical specimen is loaded to failure in diametral compression applied along the entire length.

spray drying—a method of evaporating the liquid from a solution or dispersion by spraying it into a heated gas.

spray lime—see lime, spray.

sprayed concrete—see shotcrete (preferred term).

sprayed mineral fiber—a blend of mineral fibers and inorganic binders to which water is added during the spraying operation.

sprayed mortar—see shotcrete.

spray-up application—technique in which continuous-strand roving is fed into a chopper gun, which chops the roving into predetermined lengths and simultaneously sprays the chopped fibers and a cementing matrix onto a surface.

spread footing—a generally rectangular prism of concrete, larger in lateral dimensions than the column or wall it supports, to distribute the load of a column or wall to the subgrade.

spreader—(1) a piece of lumber, usually about 1 by 2 in. (25 by 50 mm), cut to the thickness of a wall or other formed element and inserted in the form to hold it temporarily at the correct dimension against tension of form ties; wires are usually attached to spreaders so they can be pulled up out of the forms as the pressure of concrete permits their removal; and (2) a device consisting of reciprocating paddles, a revolving screw, or other mechanism for distributing concrete to required uniform thickness in a paving slab.

spreader, concrete—a machine, usually carried on side forms or on rails parallel thereto, designed to spread concrete from heaps already dumped in front of it, or to receive and spread concrete in a uniform layer.

spreader, form—see spreader.

spud vibrator—see vibrator, spud.

spun concrete—see concrete, centrifugally cast (preferred term).

stabilizer—a substance that makes either a solution or suspension more stable, usually by keeping particles from precipitating.

stacking tube—a slender, free-standing tubular structure used to store granular materials; the material is loaded into the top of the tube and spills out of wall openings to make a conical pile surrounding the tube.

stage grouting—see grouting, staged.

stain—discoloration by foreign matter.

stalactite—a downward-pointing deposit formed as an accretion of mineral matter produced by evaporation of dripping water from the surface of rock or of concrete, commonly shaped like an icicle. (See also stalagmite.)

stalagmite—an upward-pointing deposit formed as an accretion of mineral matter produced by evaporation of dripping water from the surface of rock or of concrete, commonly conical in shape. (See also stalactite.)

standard—(1) a physical reference used as a basis for comparison or calibration; (2) a concept that has been established by authority, custom, or agreement to serve as a model or rule in the measurement of quality or the establishment of a practice or procedure.

standard curing—see curing, standard.

standard deviation—the root mean square deviation of individual values from their average.

standard fire test—the test prescribed by ASTM E 119.

standard hook—a hook at the end of a reinforcing bar made in accordance with a standard.

standard hooked bar—see bar, standard hooked.

standard matched—tongue-and-groove lumber with the tongue and groove offset rather than centered as in center matched lumber. (See also center matched.)

standard sand—see sand, standard.

standard time-temperature curve—the graphic time table for application of temperature to a material or member for the ASTM E 119 fire test.

static load—see load, static.

static modulus of elasticity—see modulus of elasticity, static.

stationary hopper—a container used to receive and temporarily store freshly mixed concrete.

steam box—enclosure for steam-curing concrete products. (See also steam-curing room.)

steam curing—see curing, steam.

steam-curing cycle—the time interval between the start of the temperature rise period and the end of the soaking period or the cooling-off period; also a schedule indicating the duration of and the temperature range of the periods that make up the cycle.

steam-curing room—a chamber for steam curing of concrete products at atmospheric pressure.

steam kiln—see steam-curing room (preferred term).

stearic acid—a white crystalline fatty acid, obtained by saponifying tallow or other hard fats containing stearin. (See also butyl stearate.)


steel, axle—steel from carbon-steel axles for railroad cars.

steel, billet—steel, either produced directly from ingots or continuously cast, made from properly identified heats of open-hearth, basic oxygen, or electric-furnace steel, or lots of acid Bessemer steel, and conforming to specified limits of chemical composition.

steel, high-strength—steel with a high yield point; in the case of reinforcing bars, 60,000 psi (414 MPa) and greater. (See also steel, prestressing.)

steel, prestressing—high-strength steel used to prestress concrete; commonly seven-wire strands, single wires, bars, rods, or groups of wires or strands. (See also prestress; concrete, prestressed; pretensioning, and post-tensioning.)

steel reinforcement—bars, wires, strands, tendons, fibers, mesh or other steel elements that are embedded in a matrix primarily to resist tensile forces.

steel reinforcement, epoxy coated—steel bars with a fusion-bonded epoxy coating designed to increase corrosion resistance.”

steel reinforcement, high-strength—steel with a high yield point; in the case of reinforcing bars, a minimum of 60,000 psi (414 MPa) with typically higher strengths of 75,000 and 100,000 psi (517 and 690 MPa).

steel reinforcement, galvanized—steel that has been passed through a molten bath of zinc at a temperature of around 860 °F (460 °C); typically used for applications requiring the strength of steel and resistance to corrosion.

steel reinforcement, prestressinghigh-strength steel, most commonly strand, wire, or bars used to impart permanent prestress forces to concrete.

steel reinforcement, stainless—steel alloy with a minimum of 11% chromium content by mass; more resistant to corrosion compared to conventional steel reinforcement.

steel sheet—cold-formed sheet or strip steel shaped as a structural member for the purpose of carrying the live and dead loads in lightweight concrete roof construction.

steel temperature—see reinforcement, temperature.

steel trowel—see trowel.

stem bars—see bars, stem.

stepped footing—see footing, stepped.

sticky cement—see cement, sticky.

stiffback—see strongback (preferred term).

stiffening, early—the early development of an abnormal reduction in the working characteristics of a hydraulic-cement paste, mortar, or concrete, which may be further described as false set, quick set, or flash set.

stiffening, premature—see set, false and set, flash (preferred term).

stiffness—resistance to deformation.

stiffness factor—see factor, stiffness.

stirrup—reinforcement used to resist shear and diagonal tension stresses in a structural member; typically a steel bar bent into a U or box shape and installed perpendicular to or at an angle to the longitudinal reinforcement, and properly anchored; lateral reinforcement formed of individual units, open or closed, or of continuously wound reinforcement.

stitch drilling—procedure for removal of concrete with overlapping bore holes along the perimeter of the section to be removed.

stitching—a method for repair of cracks that involves drilling holes on both sides of the crack and grouting in stitching dogs (U-shaped metal units with short legs) that span the crack; may be used when tensile strength must be reestablished across major cracks.

stockhouse set—see cement, sticky and set, warehouse.

stoichiometric—(1) characterized by or being a proportion of substances or energy in a specific chemical reaction in which there is no excess of any reactant or product; and (2) proportioning based on atomic or molecular weight.

stone, cast—concrete or mortar cast into blocks or small slabs in special molds so as to resemble natural building stone.

stone, crushed—the product resulting from the artificial crushing of rocks, boulders, or large cobblestones, substantially all faces of which possess well-defined edges resulting from the crushing operation. (See also aggregate, coarse.)

stone sand—see sand, stone.

storage hopper—see stationary hopper.

straightedge—a rigid, straight piece of either wood or metal used to strikeoff or screed a concrete surface to proper grade or verify the planeness of a finished grade (see also rod, screed, and strikeoff); and (2) a highway tool for truing surfaces instead of a bull float.

straight-line theory—an assumption in reinforced concrete analysis according to which the strains and stresses in a member under flexure are assumed to vary in proportion to the distance from the neutral axis.

strain—the change in length per unit of length, in a linear dimension of a body; a dimensionless quantity that may be measured conveniently in percent, in inches per inch, in millimeters per millimeter, but preferably in millionths.

strain, unit—deformation of a material expressed as the ratio of linear unit deformation to the distance within which that deformation occurs.

strand—a prestressing tendon composed of a number of wires twisted above the center wire or core.

strand, indented—strand having machine-made surface indentations intended to improve bond.

strand grip—a device used to anchor strands.

strand wrapping—application of high tensile strand, wound under tension by machines, around circular concrete or shotcrete walls, domes, or other tension-resisting structural components.

stratification—the separation of overwet or overvibrated concrete into horizontal layers with increasingly lighter material toward the top; water, laitance, mortar, and coarse aggregate tend to occupy successively lower positions in that order; a layered structure in concrete resulting from placement of successive batches that differ in appearance; occurrence in aggregate stockpiles of layers of differing grading or composition; a layered structure in a rock foundation.

Stratling’s compound—dicalcium aluminate monosilicate- 8-hydrate, a compound that has been found in reacted lime-pozzolan and cement-pozzolan mixtures.

strength—the ability of a material to resist strain or rupture induced by internal or external forces.

strength, bond—resistance to the separation of mortar and concrete from reinforcing and other materials with which it is in contact; a collective expression for forces such as adhesion, friction due to shrinkage, and longitudinal shear in the concrete engaged by the bar deformations that resist separation.

strength, cold—the compressive or flexural strength of refractory concrete determined before drying or firing.

strength, compressive—the measured maximum resistance of a test specimen to axial compressive loading; expressed as force per unit cross-sectional area; or the specified resistance used in design calculations.

strength, cube—the load per unit area at which a standard cube fails when tested in a specified manner.

strength, cylinder—see strength, compressive and strength, splitting tensile.

strength, design—nominal strength of a member multiplied by a strength-reduction (Φ) factor. (See also strength, nominal and factor, phi.)

strength, dried—the compressive or flexural strength of refractory concrete determined within three hours after first drying in an oven at 220 to 230 F (105 to 110 C) for a specified time.

strength, early—strength of concrete or mortar usually as developed at various times during the first 72 h after placement.

strength, fatigue— the greatest stress that can be sustained for a given number of stress cycles without failure.

strength, fired—the compressive or flexural strength of refractory concrete determined upon cooling after first firing to a specified temperature for a specified time.

strength, flexural—the property of a solid that indicates its ability to resist failure in bending; in concrete flexural members, the stress at which a section reaches its maximum usable bending capacity; for under-reinforced concrete flexural members, the stress at which the compressive strain in the concrete reaches 0.003; for over-reinforced concrete flexural members, the stress at which the compressive stress reaches 85% of the cylinder strength of the concrete; for unreinforced-concrete members, the stress at which the concrete tensile strength reaches the modulus of rupture.(See also modulus of rupture.)

strength, nominal—strength of a member or cross section calculated in accordance with provisions and assumptions of the strength design method before application of any strength-reduction (Φ) factor.

strength, nominal flexural—the flexural strength of a member or cross section calculated in accordance with provisions and assumptions of the strength-design method before application of any strength-reduction (Φ) factor.

strength, nominal shear—the shear strength of a member or cross section calculated in accordance with provisions and assumptions of the strength-design method before application of any strength-reduction (Φ) factor.

strength, offset yield—the stress at which the strain exceeds, by a specified amount, an extension of the initially proportional part of the stress-strain curve; expressed either as a percentage of the original gage length in conjunction with the strength value (yield strength at… percent offset =…psi) or as force per unit area ([psi] or [MPa].)

 strength, pull-off—the tensile bond strength or tensile strength calculated by dividing the tensile load at failure by the area of the test specimen.

strength, required—strength of a member or cross section required to resist factored loads or related internal moments and forces in such combinations as are stipulated in the applicable code or specification.

strength, shear—the maximum shearing stress a flexural member can support at a specific location as controlled by the combined effects of shear forces and bending moment.

strength, shear-bond—a measure of the ability of a repair to resist shear stresses along the interface between the repair material and the concrete substrate.

strength, slant-shear bond—adhesive bond strength measured by applying a compressive force to a cylinder or prism that is comprised of two segments joined along a surface diagonal to the direction of the compressive force.

strength, splitting tensile—tensile strength of concrete determined by a diametrical compression test.

strength, tensile—maximum unit stress that a material is capable of resisting under axial tensile loading; based on the cross-sectional area of the specimen before loading.

strength, tensile bond—the unit stress, applied in direct tension, required to separate a hardened repair material from other materials with which it is in contact with failure occurring in or near the bonded interface.

strength, transfer—the concrete strength required before stress is transferred from the stressing mechanism to the concrete.

strength, transverse—see strength, flexural and modulus of rupture.

strength, ultimate—an obsolete term; see strength, nominal.

strength, yield—the engineering stress at which a material exhibits a specific limiting deviation from the proportionality of stress to strain.

strength-design method—a design method that requires service loads to be increased by specified load factors and computed nominal strengths to be reduced by the specified phi (φ) factors.

strength-reduction factor—see factor, strength-reduction.

strengthening—the process of restoring the capacity of weakened components or elements to their original design capacity or increasing the strength of components or elements of a concrete structure. (See also strengthening, external.)

strengthening, active—systems that typically engage the structure instantaneously; may be accomplished by introducing external forces to a member that counteract the effects of internal forces.

strengthening, external—application of bonded or anchored reinforcing or post-tensioning elements, e.g., steel or fiber-reinforced polymer composites, on exterior of structural members to increase the flexural, shear, or axial strength, or ductility of existing structural elements; external strengthening elements include plates, wraps, tendons, and the like.

strengthening, passive—systems that are typically engaged only when additional loads, beyond those existing at the time of installation, are applied to the structure; includes steel plates or fiber-reinforced polymer (FRP) composites bonded to members.

strengthening, primary—type of system required when design service loads (without load factors) exceed the nominal strength of an unstrengthened element; includes section enlargement, span shortening, and supplemental supports.

strengthening, section enlargement—placement of additional concrete on an existing structural concrete member; addition may be reinforced structural concrete to increase load-carrying capacity or protective concrete to improve fire resistance or protect against mechanical and environmental damage.

strengthening, span shortening—erection of new intermediate supports some distance from existing supports for an overstressed member; includes vertical columns, diagonal bracing, and lateral beams.

strengthening, supplemental—type of system appropriate for situation where design service loads (without load factors) are less than the existing capacity of unstrengthened element.

stress—intensity of internal force (i.e., force per unit area) exerted by either of two adjacent parts of a body on the other across an imagined plane of separation; when the forcesare parallel to the plane, the stress is called shear stress;when the forces are normal to the plane, the stress is callednormal stress; when the normal stress is directed towardthe part on which it acts, it is called compressive stress;when the normal stress is directed away from the part onwhich it acts, it is called tensile stress.

stress, allowable—maximum permissible stress used in the design of members of a structure and based on a factor of safety against rupture or yielding of any type.

stress, anchorage bond—the bar forces divided by the product of the bar perimeter or perimeters and the embedment length.

stress, bond—the force of adhesion per unit area of contact between two bonded surfaces, such as concrete and reinforcing steel, or any other material, such as foundation rock; shear stress at the surface of a reinforcing bar, preventing relative movement between the bar and the surrounding concrete when the bar carries tensile force.

stress, compressive—see stress.

stress, effective—see prestress, effective.

stress, final—in prestressed concrete, the stress that exists after substantially all losses have occurred.

stress, jacking—the maximum stress occurring in a prestressed tendon during stressing.

stress, mean—the average of the maximum and minimum stress in one cycle of fluctuating loading (as in a fatigue test); tensile stress is considered positive and compressive stress, negative.

stress, normal— the stress component that is perpendicular to the plane on which the force is applied; designated tensile if the force is directed away from the plane and compressive if the force is directed toward the plane. (See also stress.)

stress, principal—maximum and minimum stresses at any point acting at right angles to the mutually perpendicular planes of zero shearing stress, which are designated as the principal planes.

stress, proof—stress applied to materials sufficient to produce a specified permanent strain; a specific stress to which some types of tendons are subjected in the manufacturing process as a means of reducing the deformation of anchorage, reducing the relaxation of steel, or ensuring that the tendon is sufficiently strong.

stress, shear—the stress component acting tangentially to a plane.

stress, temperature—stress in a structure or a member due to changes or differentials in temperature in the structure or member.

stress, temporary—a stress that may be produced in a precast-concrete member or in a component of a precast-concrete member during fabrication or erection, or in cast-in-place concrete structures due to construction or test loadings.

stress, tensile—see stress.

stress, thermal—see stress, temperature.

stress, torsional—the shear stress on a transverse cross section resulting from a twisting action.

stress, ultimate shear—see strength, shear.

stress, working—maximum permissible design stress using working-stress design methods.

stress corrosion—the process in which the damage caused by stress and corrosion acting together is significantly greater than that produced when they act individually.

stress-corrosion cracking—see cracking, stress-corrosion.

stress relaxation—the time-dependent decrease in stress in a material held at constant strain. (See also flow, plastic and creep.)

stress-strain diagram—a diagram in which corresponding values of stress and strain are plotted against each other; values of stress are usually plotted as ordinates (vertically) and values of strain as abscissas (horizontally).

stresses, initial—the stresses occurring in prestressed-concrete members before any losses occur.

stressing end—in prestressed concrete, the end of the tendon at which the load is applied when tendons are stressed from one end only.

stretcher—a masonry unit laid with its length horizontal and parallel with the face of a wall or other masonry member. (See also header.)

strike—see striking.

strikeoff—to remove material in excess of that which is required to fill the form or repair cavity evenly and bring the surface to grade; performed with a straightedge piece of wood or metal by means of a forward sawing movement or by a power operated tool appropriate for this purpose; also the name applied to the tool. (See also screed and screeding.)

striking—the releasing or lowering of centering or other temporary support.

stringer—a secondary flexural member that is parallel to the longitudinal axis of a bridge or other structure. (See also beam.)

stringing mortar—see mortar, stringing.

strip—to remove formwork or a mold; also a long thin piece of wood, metal, or other material. (See also demold and stripping.)

strip, cant—see strip, chamfer (preferred term).

strip, chamfer—either a triangular or curved insert placed in an inside form corner to produce either a rounded or flat chamfer or to form a rustication; also called cant strip, fillet, dummy joint, and skew back.

strip, grade—usually a thin strip of wood tacked to the inside surface of forms at the elevation to which the top of the concrete lift is to rise, either at a construction joint or the top of the structure.

strip, kick—see kicker.

strip, middle—in flat-slab framing, the slab portion that occupies the middle half of the span between columns. (See also column strip.)

strip, panel—a strip extending across the length or width of a flat slab for structural design and construction or for architectural purposes.

strip, rustication—a strip of wood or other material attached to a form surface to produce a groove or rustication in the concrete.

strip, slab—see strip, middle (preferred term).

strip, wrecking—small piece or panel fitted into a formwork assembly in such a way that it can be easily removed ahead of main panels or forms, making it easier to strip those major form components.

strip footing—see footing, continuous.

strip foundation—see foundation, strip.

stripper—a liquid compound formulated to remove coatings by either chemical or solvent action, or both.

stripping—the removal of formwork or a mold. (See also demold.)

strips, divider—in terrazzo work, nonferrous metal or plastic strips of different thicknesses, usually embedded from 5/8 to 1-1/4 in. (10 to 40 mm), used to form panels in the topping.

strongback—a frame attached to the back of a form or precast structural member to stiffen or reinforce the form or member during concrete placing operations or handling operations.

structural adhesive—a bonding agent used for transferring required loads between adherents exposed to service environments typical for the structure involved.

structural concrete—see concrete, structural.

structural end-point—the acceptance criterion of ASTM E 119, which states that the specimen shall sustain the applied load without collapse.

structural lightweight concrete—see concrete, structural lightweight.

structural sandwich construction—see construction, structural sandwich.

structural sealant—see sealant, structural.

strut—see shore.

stub wall—see wall, stub.

stuccoa hydraulic cement plaster containing fine aggregate, used for coating exterior surfaces.

stud—(1) member of appropriate size and spacing to support sheathing of concrete forms; and (2) a headed steel device used to anchor steel plates or shapes to concrete members.

styrene butadiene—a synthetic resin which is a copolymer of styrene and butadiene; available as a latex emulsion and in a form which can be dissolved in aromatic solvents to form alkali-resistant coatings.

subaqueous concrete—see concrete, underwater.

subbase—a layer in a pavement system between the subgrade and the base course, or between the subgrade and a portland-cement concrete pavement.

subgrade—the soil prepared and compacted to support a structure or a pavement system.

subgrade modulus—see coefficient of subgrade reaction.

subgrade reaction—see contact pressure and coefficient of subgrade reaction.

subpurlin—a light structural section used as a secondary structural member; in lightweight concrete roof construction, used to support the form boards over which the lightweight concrete is placed.

subsample—a sample taken from another sample.

substrate—the layer immediately under a layer of different material to which it is typically bonded; an existing concrete surface that receives an overlay, partial-depth repair, protective coating, or some other maintenance or repair procedure.

sulfate attack—either a chemical or a physical reaction or both between sulfates usually in soil or water and concrete or mortar; the chemical reaction is primarily with calcium aluminate hydrates in the cement-paste matrix, often causing deterioration.

sulfate resistance—see resistance, sulfate.

sulfate-resistant cement—see cement, sulfate-resistant.

sulfoaluminate cement—see cement, expansive, Type K.

superimposed load—see load, superimposed.

superplasticizer—see admixture, water-reducing (high range) (preferred term).

supplemental reinforcement—additional reinforcement installed in a repair section when the original reinforcement was inadequate, the reinforcement has lost cross section, or the existing member is to be strengthened.


surface, brushed—a sandy texture obtained by brushing the surface of freshly placed or slightly hardened concrete with a stiff brush for architectural effect or, in pavements, to increase skid resistance. (See also finish, broom.)

surface, specific—the surface area of particles or of air voids contained in a unit mass or unit volume of a material; in the case of air voids in hardened concrete, the surface area of the air-void volume expressed as square inches per cubic inch or square millimeters per cubic millimeter.

surface active—having the ability to modify surface energy and to facilitate wetting, penetrating, emulsifying, dispersing, solubilizing, foaming, frothing, etc., of other substances.

surface-active agent—agent, surface-active.

surface air voids—small regular or irregular cavities, usually not exceeding 15 mm in diameter, resulting from entrapment of air bubbles in the surface of formed concrete during placement and consolidation. (See also sack rub.)

surface area—see surface, specific.

surface bonding (of masonry)—bonding of dry-laid masonry by parging with a thin layer of fiber-reinforced mortar.

surface hardeners—metallic particles or hard mineral aggregate usually passing No. 16 sieve size, mixed with cement; generally applied by sprinkling on the surface of plastic concrete, or other repair material, and repeated troweling to produce a dense layer.

surface impregnants—low viscosity, surface penetrating liquids which impart a degree of water repellency to the surface.

surface moisture—see moisture, surface.

surface preparation—the process whereby a method or combination of methods is used to remove deteriorated or contaminated concrete and roughen and clean a substrate to enhance bond of a repair material or protective coating.

surface profile—the topographic contour of the exposed surface of a material or substrate.

surface repair—repair of a concrete surface, e.g., application of an overlay, or repair of near-surface concrete that constitutes only a small portion of the depth of a member or element. (See also repair, partial-depth.)

surface retarder—see retarder, surface.

surface sealers—(1) in epoxy injection, the material placed over cracks to contain the liquid adhesive during the injection process before the adhesive gels. (2) protective surface treatments 10 mils (0.25 mm) or less in thickness which are generally applied with brush, roller, squeegee, or spray.

surface tension—an internal molecular force that exists in the surface film of all liquids and tends to prevent the liquid from flowing.

surface texture—degree of roughness or irregularity of the exterior surfaces of aggregate particles and also of hardened concrete.

surface vibrator—see vibrator, surface.

surface voids—see voids, surface.

surface water—see moisture, surface (preferred term).

surfactant—a shortened form of the term “surface-active agent.”

surkhi—a pozzolan consisting of burned clay powder principally produced in India.

suspension—a relatively coarse, noncolloidal dispersion of solid particles in a liquid.

sustained modulus of elasticity—see modulus of elasticity, sustained.

sway brace—a diagonal brace used to resist wind or other lateral forces. (See also bracing; cross bracing; and Xbrace.)

swelling—increase in either length or volume. (See also contraction; expansion; volume change; and volume change, autogenous.)

swift—a reel or turntable on which prestressing tendons are placed to facilitate handling and placing.

swirl finish—see finish, swirl.

Swiss hammer—see hammer, rebound (preferred term).

syneresis—the contraction of a gel, usually evidenced by the separation from the gel of small amounts of liquid; a process possibly significant in the bleeding and cracking of fresh hydraulic-cement mixtures.

syngenite—potassium calcium sulfate hydrate, a compound sometimes produced during hydration of portland cement, found in deteriorating portland-cement concrete and said to form in portland cement during storage by reaction of potassium sulfate and gypsum.

synthetic fibers—see fibers, synthetic.


system, one-way—the arrangement of steel reinforcement within a slab that presumably bends in only one direction.

system, two-way—a system of reinforcement; bars, rods, or wires placed at right angles to each other in a slab and intended to resist stresses due to bending of the slab in two directions.

Système International—see SI.

systems building—see industrialized building.

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