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.)
safe leg load see load, safe leg.
sagging see sloughing (preferred term).
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. History
sample, composite sample obtained by blending two or more individual samples of a material.
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.
(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.
(1) granular material passing the 9.5 mm (3/8 in.) sieve and almost entirely passing the 4.75 mm (No. 4) sieve and predominantly retained on the 75 μm (No. 200) sieve, and resulting either from natural disintegration and abrasion of rock or processing of completely friable sandstone; and
(2) that portion of an aggregate passing the 4.75 mm (No. 4) sieve and predominantly retained on the 75 μm (No. 200) sieve, and resulting either from natural disintegration and abrasion of rock or processing of completely friable sandstone. (See also aggregate, fine.)
Note: the definitions are alternatives to be applied under differing circumstances. Definition (1) is applied to an entire aggregate either in a natural condition or after processing. Definition (2) is applied to a portion of an aggregate. Requirements for properties and grading should be stated in the specifications. Fine aggregate produced by crushing rock, gravel, or slag commonly is known as manufactured sand.
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. Note: standard sand is produced in two gradings.
(a) 20-30 sand standard sand, predominantly graded to pass a 850 μm (No. 20) sieve and be trained on a 600 μm (No. 30) sieve and the 150 μm (No. 100) sieve.
(b) graded sand standard sand, predominantly graded between the 600 μm (No. 30) sieve and the 150 μm (No. 100) sieve.
sand, stone fine aggregate resulting from the mechanical crushing and processing of rock. (See also aggregate, fine and sand.)
sandblast a system of cutting or abrading a surface such as concrete by 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.
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-coarse aggregate ratio ratio of fine to coarse aggregate in a batch of concrete, by mass or by volume.
sand equivalent a measure of the relative proportions of detrimental fine dust or claylike material or both in soils or fine aggregate.
sand jack see sand box.
sand-lightweight concrete see concrete, sand-lightweight.
sand-lime brick see brick, calcium-silicate (preferred term).
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 or mortar containing fine aggregate with little or no cement.
sand streak a streak of exposed fine aggregate in the surface of formed concrete, caused by bleeding.
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.
(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. History
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 using abrasive blades or discs.
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.
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.
scale the oxide formed on the surface of metal during heating. (See also scaling.)
scaling local flaking or peeling away of the near-surface portion of hardened concrete or mortar; also of a layer from metal. (See also mill scale, 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 of particles larger than a specified size by sieving.
scanning electron microscope (SEM) see microscope, scanning electron (SEM).
scarf connection see connection, scarf.
scarf joint see scarf connection (preferred term).
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.
1) to strike off a cementitious mixture lying beyond the desired plane or shape;
2) a tool for striking off the cementitious mixture surface, sometimes referred to as a strikeoff; or
3) a ribbon or pad of a cementitious mixture that is preplaced to act as a guide for maintaining the desired level as more material is placed. History
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 using a screed. (See also strikeoff.) History
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.
sealant, joint compressible material used to exclude water and solid foreign materials from joints.
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 modulus see modulus, section.
segmental member see member, segmental.
(1) nonuniform concentration of components in concrete or mortar; or
(2) nonuniform distribution of size fractions in a mass of aggregate. (See also bleeding and separation.) History
self-consolidating concrete see concrete, self-consolidating.
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-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.
(1) divergence from the mass and differential accumulation of coarse aggregate during movement of the concrete;
(2) divergence from the mass and differential accumulation of large coarse aggregate from the bulk coarse aggregate as it is being moved; or
(3) the gravitational settlement of solids from a liquid. (See also bleeding and segregation). History
separation joint see joint, isolation (preferred term).
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.
separator, air an apparatus that separates various size fractions of ground materials pneumatically; fine particles are discharged as product; oversize is 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.
service dead load see load, service dead.
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; premature stiffening, hesitation set, early stiffening, and rubber set are terms referring to the same phenomenon, but false set is the preferred designation. (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 the length of time required to set or harden resin or adhesive under heat or pressure. History
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 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.
shearhead assembled unit in the top of the columns of flat slab or flat plate construction to transmit loads from slab to column.
shear modulus see modulus of rigidity.
shear reinforcement see reinforcement, shear.
shear strength see strength, shear.
shear stress see stress, shear.
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 an enclosure in which post-tensioning tendons are encased to prevent bonding during concrete placement. (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.
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, 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 and 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 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.
shotcrete concrete placed by a high velocity pneumatic projection from a nozzle. History
shotcrete, dry-mix shotcrete in which most of the mixing water is added at the nozzle. History
shotcrete, wet-mix shotcrete in which the ingredients, including water, are mixed before introduction into the delivery hose. History
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 decrease in either length or volume.
Note: may be restricted to effects of moisture content or chemical changes.
shrinkage, carbonation shrinkage resulting from 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 takes place before cement paste, mortar, grout, or concrete sets.
shrinkage, settlement a reduction in volume of concrete before the final set of cementitious mixtures, caused by settling of the solids and displacement of fluids. (See also shrinkage, plastic, and volume change, autogenous.)
shrinkage-compensating a characteristic of grout, mortar, or concrete made using expansive cement in which volume increases after setting, and if properly elastically restrained, induces compressive stresses that 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 loss see loss, shrinkage.
shrinkage reinforcement see reinforcement, shrinkage.
shuttering see formwork.
SI (Systθme 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.
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; Stratlings 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 a resin, characterized by water-repellent properties, in which the main polymer chain consists of alternating silicon and oxygen atoms, with carbon-containing side groups; silicones may be used in caulking or coating compounds or as admixtures for concrete.
sill see mud sill.
silt a granular material resulting from the disintegration of rock, with grains largely passing a 75 μm (No. 200) sieve; alternatively, such particles in the range from 2 to 50 μm diameter.
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.
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 or column capitals or both. (See also plate, flat.)
slab, ribbed see panel, ribbed.
slab bolster see bolster, slab.
slabjacking the process of either raising concrete pavement slabs or filling voids under them, or both, by injecting a material (cementitious, noncementitious, or asphaltic) under pressure.
slab-on-ground a slab cast directly on the ground. May be structural or non-structural. Structural slabs-on-ground are a required part of a load path which transmits vertical or lateral loads to the ground and must conform to applicable structural building codes. Non-structural slabs-on-ground serve only as an architectural wearing surface and are not subject to structural building code requirements. History
slab spacer see spacer, slab.
slab strip see strip, middle (preferred term).
slag see blast-furnace slag.
slag activity index see index, slag activity.
slag cement see cement, slag.
slate a fine-grained metamorphic rock possessing a well-developed fissility (slaty cleavage), usually not parallel to the bedding planes of the rock.
(1) 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; and
(2) a device used around an anchor to accommodate adjustment and preloading of the anchor after the concrete has hardened. History
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 pipe line 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 and concrete in stressed reinforced concrete, indicating anchorage breakdown.
slip, anchorage see deformation, anchorage or slip.
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, generally due to excessive water in the mixture; also called sagging. History
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. History
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.
snow load see load, snow.
soaking period see period, soaking.
soffit the underside of a part or member of a structure, such as a beam, stairway, or arch.
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-unit masonry see masonry, solid-unit.
solid volume see volume, absolute.
solubility the amount of one material that will dissolve in another, generally expressed as mass percent, or as volume percent, or parts per 100 parts of solvent by mass or volume at a specified temperature.
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.
sonic modulus see modulus of elasticity, dynamic.
sounding well a vertical conduit in the mass of coarse aggregate for preplaced-aggregate concrete, provided with continuous or closely spaced openings to permit entrance of grout; the grout level is determined by means of a float on a measured line.
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, the action of weather, pressure, or expansion within the larger mass. History
spalling the development of spalls.
span distance between the support reactions of members carrying transverse loads.
span-depth ratio the numerical ratio of total span to member depth.
span, effective the lesser of the two following distances: (a) the distance between supports; (b) the clear distance between supports plus the effective depth of the beam or slab.
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, dash-bond and parge.)
specific gravity, absolute ratio of the mass (referred to a vacuum) of a given volume of a solid or liquid at a stated temperature to the mass (referred to a vacuum) of an equal volume of gas-free 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.
specified compressive strength see strength, specified compressive.
specified compressive strength of concrete (fc') see concrete, specified compressive strength of (fc').
specified concrete compressive strength see strength, specified concrete compressive.
specified concrete equivalent strength see strength, specified concrete equivalent
specimen a piece or portion of a sample used to make a test.
spectrophotometer instrument for measuring 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 one reinforcing bar to another by lapping, welding, mechanical couplers, or other means; connection of welded-wire fabric by lapping; connection of piles by mechanical couplers.
splice, contact a means of connecting reinforcing bars in which the bars are lapped and in direct contact. (See also splice, lap).
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.
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 block see split-face block.
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.
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.
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.
staged grouting see grouting, staged.
stain discoloration by foreign matter.
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.
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 on 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 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 bar or wire reinforcement oriented normal to or at an acute angle to the longitudinal reinforcement in a flexural member and extending as close as practical to the extreme tension and compression fibers of the cross section. (See also tie.) History
stockhouse set see cement, sticky and set, warehouse.
(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
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 that possess well-defined edges resulting from the crushing operation. (See also aggregate, coarse.)
stone sand see sand, stone.
storage hopper see stationary hopper.
(1) a rigid, straight piece of either wood or metal used to strikeoff or screed a concrete surface to proper grade or to check 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 millimeters, 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, compacted prestressing strand that is drawn through a circular die to deform the wires and produce a strand with a smaller circular shape. History
strand, indented strand having machine-made surface indentations intended to improve bond. History
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 placing 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.
Stratlings compound dicalcium aluminate monosilicate-8-hydrate, a compound that has been found in reacted lime-pozzolan and cement-pozzolan mixtures.
strength a generic term for the ability of a material to resist strain or rupture induced by external forces. (See also strength, concrete compressive; strength, fatigue; strength, flexural; strength, shear; strength, splitting tensile; strength, tensile; strength, ultimate; and strength, yield.) History
strength, bond resistance to 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, concrete compressive the measured maximum resistance of a concrete specimen to axial compressive loading; expressed as force per unit cross sectional area. History
strength, cube the load per unit area at which a standard cube fails when tested in a specified manner.
strength, cylinder see strength, concrete compressive and strength, splitting tensile.
strength, design nominal strength multiplied by a strength reduction factor φ. (See also strength, nominal and factor, phi.) History
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 hours 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 material or a structural member 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. History
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 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, 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, specified compressive compressive strength of concrete used in design. History
strength, specified concrete compressive the specified resistance of a concrete specimen to axial compressive loading used in design calculations and as a criterion for material proportioning and acceptance. History
strength, specified concrete equivalent in-place concrete compressive strength adjusted by correction factors that can be directly substituted into conventional strength equations with customary strength reduction factors. History
strength, splitting tensile tensile strength of concrete determined by a splitting tensile 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. History
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 stress at which a material exhibits a specific limiting deviation from the proportionality of stress to strain. History
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.
stress force per unit area. History
stress, allowable maximum permissible stress used in 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 corrosion of a metal either initiated or accelerated by stress.
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 concrete in excess of that which is required to fill the form evenly or bring the surface to grade; performed with a straightedged 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.) History
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 load test see load test, structural.
structural repair see repair, structural.
structural sandwich construction see construction, structural sandwich.
strut see shore.
stub wall see wall, stub.
stucco a portland cement-based plaster used for coating exterior walls and other exterior surfaces. (See also plaster.) History
(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.
subaqueous concrete see concrete, underwater.
subbase the layer in a pavement system between the subgrade and the base course, or between the subgrade and the pavement. History
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.
subsieve fraction particles all of which pass through a U.S. Standard 45 μm (No. 325) sieve.
substrate Any material on the surface of which another material is applied. History
substructure all of that part of a structure below grade.
sulfate attack either a chemical or a physical reaction or both between sulfates usually in soil or ground 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).
superstructure all of that part of a structure above grade.
supersulfated cement see cement, supersulfated.
supplementary cementitious material (SCM) see material, supplementary cementitious (SCM).
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 moisture see moisture, surface.
surface retarder see retarder, surface.
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.
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 X-brace.)
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 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.
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.
Systθme International see SI.
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