Concrete and paving glossary - S

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Sack

A quantity of Portland cement; 94 pounds in the United States, 87.5 pounds in Canada, 112 pounds in the United Kingdom, and 50 kilograms in most other countries. Different weights per bag are commonly used for other types of cement.

Sack mix

The amount of Portland cement in a cubic yard of concrete mix. Generally, 5 or 6 sacks is required in a foundation wall.

Sack rub (sack finish)

A finish for formed concrete surfaces, designed to produce even texture and fill all pits and air holes. After dampening the surface, and before it dries, a mixture of dry cement and sand is rubbed over it with a wad of burlap or a sponge-rubber float to remove surplus mortar and fill the voids.

Sacking

Removing or alleviating defects on a concrete surface by applying a mixture of sand and cement to the moistened surface and rubbing with a coarse material such as burlap.

S/B division plate

See division plate (slotted for rebar).

Scab

A short piece of wood fastened to two formwork members to secure a butt joint or joining pieces of wood together to make a longer one.

Scaling

The breaking away of a hardened concrete surface.

Screed

To level off concrete to the correct elevation during a concrete pour. To strike off concrete lying above the desired plane or shape. A screed is also a tool for striking off the concrete surface, sometimes referred to as a strike off. See strike off.

Screed bar

The screed bar holder is an "L" shaped device that attaches to the top of a stake and onto which a pipe (screed bar) is attached at the finish grade level. The finishing screed then rides on top of this pipe (screed bar) to prevent the full weight of the screed from being placed on the fresh concrete during the finishing process. See screed.

Screed bar holders

(1) A metal bracket designed to hold a screed bar in place during concrete finishing activities.

(2) Concrete flatwork forming accessories that attach to either a nail stake or a form pin with a clamp and then hold a screed bar in place. A finishing screed will then be pulled to finish the concrete. See form pins, screed, screed bar.

Screed coat

The plaster coat made flush with the screeds.

Screed guide

Firmly established grade strips or side forms for unformed concrete that will guide the strike off in producing the desired plane or shape. See screed and strike off.

Screed post

An adjustable metal post that sits on top of a nail stake or form pin and is then adjusted up or down by rotating a threaded rod. A screed bar rests in a cradle on top of the screed bar post and a finishing screed is then pulled across to finish the concrete. See screed.

Screed rail

Grade strips or side forms for concrete that will also guide the strike off in screeding. See screed and strike off.

Screeding

The operation of forming a surface by the use of screed guides and a strike off. See screed and strike off.

Seawall form

(1) Barriers, often made from concrete, that act to reduce the erosion caused by moving or tidal water.

(2) A specialized form to place concrete in a variety of applications where flood or erosion concerns, or containment requirements exist. Applications include boat docks, channels, water treatment plants, fisheries, and flood control. See custom forms.

Segregation

The separation of the components of wet concrete caused by excessive handling or vibration. The differential concentration of the components of mixed concrete, aggregate, or the like, resulting in non-uniform proportions in the mass. See separation.

Separation

The tendency of coarse aggregate to separate from the concrete and accumulate at one side as concrete passes from the unconfined ends of chutes, conveyor belts, or similar arrangements. See segregation.

Set

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. See curing.

Set retarders

Agents used to delay, slow down, the setting of concrete. See accelerators.

Setting shrinkage

A reduction in volume of concrete prior to the final set of cement, caused by settling of the solids and by the decrease in volume due to the chemical combination of water with cement. See shrinkage.

Settlement

Sinking of solid particles in grout, mortar, or fresh concrete, after placement and before initial set.

Shake-on hardener

A dry powder that is dusted onto the surface of a concrete slab before troweling to react with the concrete and produce a hard-wearing surface for industrial uses. See troweling.

Shock load

The impact load of material such as aggregate or concrete as it is released or dumped during placement. See aggregate and concrete.

Shotcrete

Mortar or concrete pneumatically projected at high velocity onto a surface. Also known as air-blown mortar. Pneumatically applied mortar or concrete, sprayed mortar, and gunned concrete. See concrete.

Shrinkage

A volume decrease caused by drying and/or chemical changes, such as of concrete or wood.

Sitecast concrete

Concrete that is poured and cured in its final position at a construction project. See pre-cast concrete and ready-mixed concrete.

Slab, concrete

Concrete pavement that would be found in driveways, garages, and basement floors.

Slab on grade

A type of foundation with a concrete floor that is placed directly on the soil. The edge of the slab is usually thicker and acts as the footing for the walls.

Slag

Concrete cement that sometimes covers the vertical face of the foundation void material.

Sleeve(s)

Pipe installed under the concrete driveway or sidewalk, and that will be used later to run sprinkler pipe or low voltage wire.

Slide bar

A metal bar on which a variety of forming accessories can be attached and slid into the desired position. Accessories that are often attached to a slide bar include stake pockets, and hanger brackets. See slide pockets and stake pockets.

Slide pocket

Stake pockets configured to mount on a slide bar. The slide pocket can be positioned wherever necessary on the slide bar and then used to anchor to the accessories and to the ground. See slide bar.

Sliding nose form

A metal concrete pouring form manufactured with a sliding nose piece that retracts to allow adjacent forms to be removed from the pour without removing forms from either side of the form with the sliding nose. Using this type of form is the only way forms can be easily removed from a pour when using pouring dowels or rebar. See fixed nose form and rebar.

Slip form

A form which is raised or pulled as concrete is placed; may move vertically to form wails, stacks, bins or silos, usually of uniform cross section from bottom to top; or a generally horizontal direction to lay concrete evenly for highways, on slopes and inverts of canals, tunnels, and siphons.

Slip forming

The process of simultaneously extruding and finishing concrete pavement, curb and gutter combinations, median barriers, and like applications using a paving machine. See paving machine.

Building multi-story sitecast concrete walls with forms that rise up as the wall construction progresses. See sitecast concrete.

Slope

The incline angle of a sidewalk or road surface, given as a ratio of the rise (in inches) to the run (in feet). See pitch.

Slump

The "wetness" of concrete. A 3 inch slump is dryer and stiffer than a 5 inch slump. See slump cone, slump loss, and slump test.

Slump cone

A mold in the form of the lateral surface of the frustum of a cone with a base diameter of 8" (203 mm), top diameter 4" (102 mm), and height 12" (305 mm), used to fabricate a specimen of freshly mixed concrete for the slump test. A cone 6" (152 mm) high issued for tests of freshly mixed mortar and stucco. See slump, slump loss, and slump test.

Slump loss

The amount by which the slump of freshly mixed concrete changes during a period of time after an initial slump test was made on a sample or samples thereof. See slump, slump cone, and slump test.

Slump test

This is a test to determine the plasticity of concrete. A sample of wet concrete is placed in a cone-shaped container 12" high. The cone is removed by slowly pulling it upward. If the concrete flattens out into a pile 4" high, it is said to have an 8" slump. This test is done on the job site. If more water is added to the concrete mix, the strength of the concrete decreases and the slump increases. See Kelly ball, slump, slump cone, and slump loss.

Slurry

A mixture of water and any finely divided insoluble material, such as Portland cement, slag, or clay in suspension. See Portland cement.

Sonotube

A round, large cardboard tube designed to hold wet concrete in place until it hardens.

Spall

A fragment, usually of flaky shape, detached from a larger mass by pressure, expansion from within the larger mass, a blow, or by the action of weather.

Spalling

The chipping or flaking of concrete, bricks, or other masonry where improper drainage or venting and freeze/thaw cycling exists. See spaul, spauling or spauled concrete.

Spaul, spauling or spauled concrete

The unwanted condition when small surface sections of a concrete slab peel off or chip away. This condition due to the over use of salt, numerous freeze/thaw cycles, or an inferior concrete mix. Same as spalling.

Specifications or Specs

A narrative list of materials, methods, model numbers, colors, allowances, and other details which supplement the information contained in the blue prints. Written elaboration in specific detail about construction materials and methods. Specs are written to supplement working drawings.

Spring Steel

A high alloy metal that will spring back to its original shape after being formed or bent into another shape. It is often used to manufacture flexible forms. See flexible forms.

Squeegee

Fine pea gravel used to grade a floor, normally before concrete is placed. See placement.

Stacking

A metal angle, welded to metal forms and nailed to wood forms, that helps secure the form in place when a form pin is driven through the pocket and anchored by small metal wedges designed into the pocket. See curb and gutter forms, form pins, straight form, flexible form, nail stakes, super flat forms, and transition forms.

Stake

A short, pointed piece of wood or metal driven into the ground as a marker or an anchor.

Often used with wood or metal forms to anchor them into place during concrete placement.

See cold-rolled solid steel form pins, form pins, flat stakes, flatwork forms, hot-rolled solid steel form pins, and nail stakes.

 

Stake pockets

"V" shaped components that are welded to the back of straight forms or riveted to the back of flexible forms. A forming stake or pin is inserted in the “V", hammered into the ground to anchor the form securely, and held in place with a wedge. See flexible forms and straight forms.

Stake puller

A metal device which acts as a fulcrum with a pivot that is used to remove metal stakes hammered into the ground to secure wooden or metal concrete forms.

Steam curing

Curing of concrete or mortar in water vapor at atmospheric or higher pressures and at temperatures between about 100° and 420° F (40° and 215° C).

Steel trowel

A smooth concrete finish obtained with a steel trowel. It is also a tool used for non-porous smooth finishes of concrete. It is a flat steel tool used to spread and smooth plaster, mortar or concrete. Pointing trowels are small enough to be used in places where larger trowels will not fit. The pointing trowel has a point. The common trowel has a rectangular blade attached to a handle. For a smooth finish, the steel trowel is used when the concrete begins to stiffen. See trowel.

Steel troweling

A steel hand tool or machine used to create a dense, smooth finish on a concrete surface. See troweling.

Straight filler forms

A metal form used to fill in sections in concrete placements where a form length of less than 10'is needed for any flatwork application. Straight filler forms are designed to slip over the top rails of the forms to be joined. These forms are sometimes referred to as rehab forms. See flatwork forms and straight forms.

Straight forms

Formed metal channels, typically 10 feet long, with a height that varies from 4" to 24" and used for straight concrete forming and pours. The width of the base can vary between 2" and 4" dependent on form height and application. The top rail of the form is typically 2" wide. Applications for straight forms include, front and back form for curb and gutter setups, sidewalks, patios, retaining walls, foundation footers, and similar applications. See corner forms, filler forms, flexible forms, keyway forms, radius forms, reversible forms, tilt-up forms, tilt-up reversible forms, and transition forms.

Straightedge

A rigid and straight, piece of wood or metal used to strike off or screed a concrete surface to the proper grade, or to check the flatness of a finished grade. See also rod, screed, and strike off.

Strategic Highway Research Program (SHRP)

A research program designed to produce better techniques and materials in the areas of concrete structures, asphalt, pavement performance, and highway operations.

Strike off

To remove concrete in excess of that which is required to fill the form evenly or bring the surface to grade, performed with a straight-edged piece of wood or metal by means of a forward sawing movement or by a power-operated tool appropriate for this purpose. The name applied to the tool used to fill the form evenly. See screed.

Stripping

Removing the formwork from concrete. See formwork.

Stripping agent

See release agent.

Stucco

Refers to an outside plaster finish made with Portland cement as its base.

Sub-base

Clay or soil material used underneath the stone base. See base course / base.

Subcontractor

A contractor who specializes in one area of construction activity and who usually works under the general contractor. See contractor and general contractor.

Super flat floor

A concrete slab finished to a high degree of flatness according to recognized systems of measurement.

Super flat forms

Forms designed to prevent "screed hop" when a rock or other debris is on the form rail and causes the screed bar to hop which creates a ripple in the pour. This ripple typically must be ground out. Super flat forms have a knife edge upon which the screed rides and causes rocks or debris sitting on the form rail to be pushed out of the way of the screed bar ensuring a flat pour. See form rail.

Superplasticizer

A concrete admixture that makes wet concrete extremely fluid without additional water. These agents perform the same function as a plasticizer, but are composed of different materials. See admixture and plasticizer.

Surface moisture

Free moisture retained on the surfaces of aggregate particles that becomes part of the mixing water in the concrete mix. See aggregate.

Swirl finish (sweat finish)

A nonskid texture imparted to a concrete surface during final troweling by keeping the trowel flat and using a rotary motion. See trowel, troweling, and trowel finish.

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