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Concrete Glossary
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Abrams' law

The rule stating that with given materials, curing, and testing conditions, concrete strength is inversely related to the ratio of water to cement. Low water-to-cement ratios produce higher strengths.

Abrasive aggregate

The aggregate used to increase the abrasiveness of the surface of a concrete slab.

Abrasion Resistance

The ability of a surface from being worn from wear and tear from regular use or abuse.

Abrasive Blasting

Using the force of an abrasive material shot at a surface at high velocity to remove, profile or etch its surface, for decorative or functional reasons. Materials include but are not limited to, sand, metal shot, or dry ice.

Absolute volume

In concrete, the actual volume occupied by the different ingredients determined by dividing the weight of each ingredient pounds, by its specific gravity, times the weight of one cubic foot of water in pounds.

Example: Absolute Volume of one sack of cement equals: 94 ÷ (3.15 x 62.4) = 0.478 cubic feet.


The process by which water is absorbed. The amount of water absorbed under specific conditions, usually expressed as percentage of the dry weight of the material.

Absorption loss

Water losses that occur until the aggregate in a concrete mix is saturated. See aggregate.


The speeding up of the setting or hardening process of concrete by using an additive in the mix. The process of acceleration allows forms to be stripped sooner or floors finished earlier. See accelerators.


Material additives used to accelerate, or reduce, the setting time of concrete causing it to harden faster. Accelerators often include calcium chloride, or aluminum sulfate or other acidic materials. See set retarders.


The items used to assemble scaffolding, shoring, and forms, other than the walers, frames, and the forms themselves in the placing of concrete. See curb and gutter forms, flatwork forms, filler forms, flexible forms, straight forms, and walers.


A colorless, volatile, extremely flammable liquid ketone, CH 3 COCH 3 , widely used as an organic solvent. Often used in decorative concrete for a quick flashing color deposit, and dilution agent for concrete sealers.

Acid Etch

The process by which an acid (often times muriatic or hydrochloric) is used to etch and prepare a cement surface for painting or the application of some type of coating system.

Acid Stain

A combination of metallic salts, muriatic acid, and water that when applied to a cement-based surface, the acid in the solution etches into the surface allowing for the metallic salts to penetrate in and react with the free lime deposits, or calcium hydroxide, in the cement. Water in the solution fuels the reaction creating colored compounds that become a permanent part of the concrete. The colors deposited create a mottled, naturally variegated pattern of color.

Chemical Acid Stains are generally available in variations of five basic color groups: Blacks, Browns, Oranges, Aged Copper & Greens - all of these shades are natural earthy mineral tones.

Adiabatic curing

The maintenance of ambient conditions during the setting and hardening of concrete so that heat is neither lost nor gained from the surroundings of the concrete.

Adjustable Hanger

A forming accessory, a metal strip, used to suspend or support metal forms or metal form attachments when traditional methods of anchoring forms or form attachments cannot be used due to trenching or prior concrete placement. See hanger.


A material, other than aggregate, cement, or water, added in small quantities to the mix in order to produce some desired modifications, either to the physical or chemical properties of the mix or of the hardened product. The most common admixtures affect plasticity, air entrainment, and curing time. These admixtures are often referred to as plasticizers, superplasticizers, accelerators, dispersants, and water-reducing agents.

Advanced Cement-Based Materials (ACBM)

A center at Northwestern University established by the National Science Foundation to create new cement-based materials with improved properties.

Aerated concrete

Concrete formed using gas-forming admixtures such as powdered zinc or aluminum combined with calcium hydroxide or hydrogen peroxide that form hydrogen or oxygen bubbles in the cement mix.


A mixture of sand, rock, crushed stone, expanded materials, or particles that typically compose 75% of concrete by volume improve the formation and flow of cement paste and improve the concrete's structural performance. See concrete.

Aggregate, exposed or exposed aggregate

A concrete surface with the aggregate exposed, formed by applying a retarder to the surface before the concrete has set, and subsequently removing the cement paste to the desired depth. See aggregate.

Aggregate testing

Any of a number of tests performed to determine the physical and chemical characteristics of an aggregate. Common tests are for abrasion, absorption, specific gravity, and soundness. See aggregate.

Agitating speed

The rate at which a concrete or mortar mixer rotates the drum or blades in order to agitate mixed materials to prevent segregation or setting. See concrete mixture, mixing speed, segregation, and set.


The rotation of, or moving of blades through, a drum containing concrete or mortar to prevent segregation or setting of mixture. See concrete and segregation.


A mechanical device used to maintain plasticity and to prevent segregation, particularly in concrete and mortar. See concrete and segregation.

Agitator truck

Vehicle designed to take pre- or ready-mixed concrete and deliver it ready to be used at a construction site. The truck bed contains a large barrel or drum that is used to continuously roll or agitate the concrete mixture keeping it from solidifying before use. See ready-mixed concrete.

Air content

The amount of entrained or entrapped air in concrete or mortar, exclusive of pore space in aggregate particles, usually expressed as a percentage of total volume of concrete or mortar.

Air-entrained agent

An additive to hydraulic cement or an admixture for concrete or mortar that causes air to be incorporated in the form of minute bubbles on the concrete or mortar during mixing, usually to increase its workability and frost resistance. See hydraulic cement.

Air-entrained concrete

A Portland cement with an admixture that causes a controlled quantity of stable, very small air bubbles to form in the concrete during mixing. See non-air-entrained concrete.

Air-permeability test

A procedure for determining the fineness of powdered material such as cement.

Air content

The volume of air present in a concrete or mortar mix, expressed as a percentage of the total volume. A controlled air content prevents concrete from cracking during the freeze/thaw cycle.

Air meter

A device for measuring the air content of a concrete or mortar mix. See air content and mix.

Air slacking

The absorption of moisture and carbon dioxide from the air by lime or cement.

Alkali-Aggregate Reaction

Older terminology for Alkali-Silica Reactivity (ASR).

Alkali-Silica Reactivity (ASR)

The reaction of aggregates, which contain some form of silica or carbonates with sodium oxides or potassium oxides in cement, particularly in warm, moist climates or environments, causing expansion, cracking or popouts in concrete.

American Association of State Highway and Transportation Officials (AASHTO)

An organization that represents highway and transportation departments in the 50 states, the District of Columbia and Puerto Rico.

American Concrete Institute (ACI)

An international organization dedicated to providing knowledge and information for the best uses of concrete .

American National Standards Institute (ANSI)

An organization that represents the United States in the International Organization for Standardization (ISO).

American Standard of Testing Materials (ASTM)

An organization that has developed a variety of methods for testing the strength of cement and other building materials to ensure it complies with needed strength requirements.

Anchor bolts

Bolts to secure a wooden sill plate to concrete, masonry floor, or wall.

Angle float (angle trowel)

A trowel with two surfaces meeting at right angles. An angle float is used for finishing plaster or concrete in an inside corner. See float and trowel.


A slab of concrete extending beyond the entrance to a building, particularly at an entrance for vehicular traffic. At an airport, the pavement adjacent to hangars and appurtenant buildings. See paving forms.

Architectural concrete

Structural or nonstructural concrete that will be permanently exposed to view and therefore requires special attention to uniformity of materials, forming, placing, and finishing. This type of concrete is frequently cast in a mold and has a pattern on the surface. See fair face concrete.

Arising tool

A special float used to round the edges of freshly placed concrete. See concrete and float.


A black petroleum residue, which can be anywhere from solid to semisolid at room temperature. When heated to the temperature of boiling water, it becomes able to be poured. It is used in roofing materials, surfacing roads, in lining the walls of water-retaining structures such as reservoirs and swimming pools, and in the manufacture of floor tiles. Asphalt should not be confused with tar, a similar looking substance made from coal or wood and incompatible with petroleum derivates.

Asphalt cement

Asphalt that has been refined to meet the specifications for use in paving and other special uses. It is classified by penetration.

Asphalt expansion joint

Remolded felt or fiberboard impregnated with asphalt and used extensively as an expansion joint for cast-in-place concrete.

Asphalt leveling course

A course of asphalt concrete pavement of varying thickness spread on an existing pavement to compensate for irregularities prior to placing the next course.


A chamber in which an environment of steam and high pressure is produced. Used in curing of concrete products and in the testing of hydraulic cement for soundness.

Autoclaved Aerated Concrete (AAC)

Autoclaved Aerated Concrete (AAC) is a mixture of Portland cement, quicklime, sand, water and aluminum powder. The chemical interaction of these "aerated" natural materials creates a porous, closed cell masonry material with a density of approximately forty-five (45) pounds per cubic foot, roughly one-third the weight of stone concrete. A high temperature, high-pressure steam cure in an autoclave speeds additional chemical reactions, which allow the AAC to reach full strength in less than twenty-four (24) hours. AAC is easy to use on a job site and provides excellent sound proofing and fire protection.

Auxiliary reinforcement

In a pre-stressed concrete member, refers to all reinforcing steel other than the pre-stressing steel. See pre-stressed concrete.


The replacement of excavated earth into a trench around or against a basement crawl space foundation wall.


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. Same as sack.

Ball test

A test to determine the consistency of freshly mixed concrete by measuring the depth of penetration of a cylindrical metal weight or plunger that has been dropped into it. See slump test.


A layer of coarse stone, gravel, slag, etc., over which concrete is placed.


A group of small bars or the wire encircling the main reinforcement in a concrete structural member to form a peripheral tie. A band is also a group of bars distributed in a slab, wall, or footing.


A deformed steel member used to reinforce concrete. See rebar and reinforced concrete.

Bar support (bar chair)

A rigid device of formed wire, plastic, or concrete, used to support or hold reinforcing bars in proper position during concrete operations. See chair and high chair.


A unit of weight measure for Portland cement, equivalent to four bags or 376 pounds. See bag.

Base course / base

A layer of material of specified thickness constructed on the sub grade or sub-base of a pavement to serve one or more functions, such as distributing loads, providing drainage, or minimizing frost action. See sub-base.


The quantity produced as the result of one mixing operation, as in a batch of concrete.

Batch box

A container of known volume used to measure the constituents of concrete or mortar in proper proportions.

Batch mixer

A machine that mixes concrete, grout, or mortar in batches in accordance to a design mix. Each batch is used completely before a second batch is started.

Batch plant

A temporary concrete mixing plant usually erected at a jobsite to fulfill the specific needs of that job. They are typically erected when a large volume of concrete will be required at a specific job. Batch plant utilization reduces transportation costs, increases control of the mixture, and speeds up job completion.


A slope, such as that of the outer side of a wall, that is wider at the bottom than at the top. The measurement of batter is the horizontal distance between the top and bottom of a slope. See curb face batter.

Batter level

An instrument used to measure the inclination of a slope. See batter.

Battered wall

A wall that slopes backward, as by recessing or sloping masonry in successive courses.


A prepared base for masonry or concrete.


See maul.

Bending schedule

A list of reinforcement prepared by the designer or detailer of a reinforced concrete structure which shows the shapes, dimensions, and location of every bar, and the number of bars required. See reinforced concrete and rebar.

Big cement

A bag of cement.


Almost any cementing material, either hydrated cement or a product of cement or lime and reactive siliceous materials. The kinds of cement and the curing conditions determine the general type of binder formed. Any material, such as asphalt or resin that forms the matrix of concretes, mortars, and sanded grouts.

Bituminous cement

A class of dark substances composed of intermediate hydrocarbons. Bituminous cement is available in solid, semisolid, or liquid states at normal temperatures.

Blaine apparatus

Air-permeability apparatus for measuring the surface area of a finely ground cement. See Blaine fineness and Blaine test.

Blaine fineness

The fineness of granular materials such as cement and puzzling, expressed as total surface area in square centimeters per gram, determined by the Blaine air-permeability apparatus and procedure. See Blaine apparatus, Blaine test, and puzzling.

Blaine test

A method for determining the fineness of cement or other material based on the permeability to air of a sample prepared under specified conditions. See Blaine apparatus and Blaine fineness.


Insulation sandwiched between sheets of fabric, plaster, or paper facing, used for protecting fresh concrete during curing. See curing.


The autogenously flow of mixing water within, or its emergence from, freshly placed concrete or mortar. Bleeding is caused by the settlement of the solid materials within the mass. Bleeding is also called water gain.

Blended cement

A hydraulic cement consisting of an intimate and uniform blend of granulated blast-furnace slag and hydrated lime, Portland cement and granulated blast-furnace slag, Portland cement and puzzling, or Portland-blast-furnace slag, cement, and puzzling. Blended cement is produced by intergrading Portland cement clinker with the other materials or by a combination of intergrading and blending. See hydraulic cement, Portland cement, and puzzling.

Block out

The installing of a box or barrier within a foundation wall to prevent the concrete from entering an area. For example, foundation walls are sometimes "blocked" in order for mechanical pipes to pass through the wall, to install a crawl space door, and to depress the concrete at a garage door location.


In concrete, a bug hole or small regular or irregular cavity, not exceeding 15 mm in diameter, resulting from entrapment of air bubbles in the surface of formed concrete during placement and compaction. See placing, placement and compaction.


Term used when the ready-mixed concrete breaks through the forming boards due to insufficient bracing. Also, the localized buckling or breaking up of rigid pavement as a result of excessive longitudinal pressure. See ready-mixed concrete.


Slang term used to describe the unexpected fast setting of concrete that does not allow proper finishing. See set.

Board foot

The basic unit of measurement for lumber. One board foot is equal to a 1" thick board, 12" in width and 1' in length. Therefore, a 10' long, 12" wide, and 1" thick piece contains 10 board feet. Nominal sizes are assumed when calculating board feet.


The adhesion of cement paste to aggregate and or the rebar. See aggregate and rebar.

Bond breaker

A strip of material to which the cement does not adhere. See bond and form release agent.

Bonded posttensioning

A process in posttensioned construction whereby the annular spaces around the tendons are grouted after stressing in a manner that the tendons become bonded to the concrete section.


A concrete forming accessory that acts as a temporary support for aligning vertical concrete formwork. One end of the brace attaches to the form and the other anchors to the ground.

British thermal unit (BTU)

A standard measurement of the heat energy required to raise the temperature of one pound of water one degree Fahrenheit.


A material that fractures easily such as cement.

Broom finish

Concrete that has been brushed with a broom when fresh in order to improve its traction or to create a distinctive fine-lined texture.

Brown millerite

An oxide of calcium, aluminum, and iron commonly formed in Portland cement and high alumina cement mixtures.

Bull float

A board of wood, aluminum, or magnesium mounted on a pole and used to spread and smooth freshly placed, horizontal concrete surfaces. After screeding, the first stage in the final finish of concrete, smoothes and levels hills and voids left after screeding. Sometimes substituted for darbying. See darby, float, and screeding.


Material often used to protect newly finished concrete from rain as well as maintaining moisture in a slab. See Visqueen and curing blanket.


A construction slang term used to describe the darkish concrete color that occurs as a result of over troweling. See trowel, troweling, and trowel finish.


A tool having a serrated face, as rows of pyramidal points, used to develop an architectural finish for concrete surfaces.

Bush-hammered concrete

Concrete with an exposed aggregate finish that has been obtained by removing the surface cement using a percussive hammer with a serrated face. See aggregate, exposed.


A hand tool used to trowel finish concrete curb and gutter work. See trowel, troweling, trowel finish, and curb and gutter


A 10" or 12" diameter hole drilled into the earth and embedded into bedrock 3 to 4 feet. The structural support for a type of foundation wall, porch, patio, monopost, or other structure. Two or more "sticks" of reinforcing bars (rebar) are inserted into and run the full length of the hole and then concrete is poured into the caisson hole. A caisson is designed to rest on an underlying stratum of rock or satisfactory soil and is used when unsatisfactory soil exists. See rebar and pouring.


The main raw material used in the manufacture of Portland cement. Calcite is a crystallized form of calcium carbonate and is the principal component in limestone, chalk, and marble.

Calcium aluminate cement

A combination of calcium carbonate and aluminates that have been thermally fused or sintered and ground to make cement.

Calcium chloride

An additive used in ready-mix to accelerate the curing, usually used during damp conditions. See ready-mixed concrete.

Capillary space

A term used to describe air bubbles that have become embedded in cement paste.

Cast-in-place concrete

Concrete that is poured into forms that are erected at the job site. It is the same as the term sitecasting. See pre-cast concrete.


Pouring a liquid material, or slurry, like concrete, into a mold or form whose physical form it will take on as it solidifies. See pouring.

Casting bed

A permanent, fixed form, in which permanent pre-cast concrete forms are produced. See pre-cast concrete, cast-in-place concrete.


A contraction meaning a cement finisher.

Cem. Fin.

The construction abbreviation for a cement finish.


A material composed of fine ground powders that hardens when mixed with water. Cement is only one component of concrete. The gray powder that is the "glue" in concrete.

Cement-aggregate ratio

The ratio of cement to aggregate in a mixture, as determined by weight or volume.

Cement content / cement factor

A quantity of cement contained in a unit volume of concrete or mortar, ordinarily expressed as pounds, barrels, or bags per cubic yard.

Cement mixer

A concrete mixer. A container used to mix concrete ingredients by means of paddles or a rotary motion. The container may be manually or power-operated.

Cement mixtures

Mixtures are always listed as parts Cement to Sand to Aggregate. Following are typical cement mixtures description:

· Rich - 1 part cement, 2 parts sand, 3 parts coarse aggregate. A rich mix is used for concrete roads and waterproof structures.

· Standard - 1 part cement, 2 parts sand, 4 parts coarse aggregate. A standard mix is used for reinforced work floors, roofs, columns, arches, tanks, sewers, conduits, etc.

· Medium - 1 part cement, 2 1/2 parts sand, 5 parts coarse aggregate. A medium mix is used for foundations, walls, abutments, piers, etc.

· Lean - 1 part cement, 3 parts sand, 6 parts coarse aggregate. A lean mix is used for all mass concrete work, large foundations, backing for stone masonry, etc.

Cement slurry

A thin, watery cement mixture for pumping or for use as a wash over a surface.

Cement types

· Type I Normal - is a general purpose cement suitable for practically all uses in residential construction but should not be used where it will be in contact with high sulfate soils or be subject to excessive temperatures during curing.

· Type II Moderate - is used where precaution against moderate sulfate attack is important, as in drainage structures where sulfate concentrations in groundwater's are higher than normal.

· Type III High Early Strength - is used when high strengths are desired at very early periods, usually a week or less. It is used when it is desirable to remove forms as soon as possible or to put the concrete into service quickly.

· Type IV Low Heat - is a special cement for use where the amount and rate of heat generated during curing must be kept to a minimum. The development of strength is slow and is intended in large masses of concrete such as dams.

· Type V Sulfate Resisting - is a special cement intended for use only in construction exposed to severe sulfate action, such as western states having soils of high alkali content.


Any material having cementing properties, usually referring to substances like Portland cement and lime. See Portland cement.

Central plant

A facility that makes and distributes ready-mix or pre-mixed concrete loading the material into agitator trucks. See ready-mixed concrete and agitator trucks.


A small metal or plastic support for reinforcing steel in concrete construction. The support is used to maintain proper positioning during concrete placement. See bar support/bar chair and high chair.

Cinder block

A masonry block made of crushed cinders and Portland cement. This type of block is lighter and has a higher insulating value than concrete. Because moisture causes deterioration of cinder block, it is used primarily for interior rather than exterior walls. See concrete block.


The resulting admixture from burning a combination of limestone with silica, alumina, and iron oxide-containing materials. A lump or ball of the fused material, usually 1/8" to 1" in diameter, is formed by heating cement slurry in a kiln. Clinker, when cool, is ground into a fine powder and interground with gypsum to form cement. See admixture.

Clip ties

Sharp, cut metal wires that protrude out of a concrete foundation wall (that at one time held the foundation form panels in place).

Coarse aggregate

Naturally occurring, processed or manufactured, inorganic particles in prescribed gradation or size range. The smallest size particle will be retained on the No. 4 sieve.

Cold joint

A visible line that forms when the placement of concrete is delayed. The concrete in place hardens prior to the next placement of concrete against it.

Cold-rolled solid steel form pins

Concrete forming metal pins made from steel that has been rolled to its final form at a temperature at which it is no longer plastic giving the pins a dense, smooth, surface finish and high tensile strength. See hot-rolled solid steel form pins.

Column clamp

A latching device for holding the sections of a concrete-column form together while the concrete is being placed.

Column form

Specialized forms for creating low height columns typically used as parking lot light anchors, communication tower bases, and similar applications where short columns are required.


The elimination of voids in construction materials, as in concrete, plaster, or soil, by vibration, tamping, rolling, or some other method or combination of methods. The process of eliminating voids in the non-set concrete mixture that has been placed often using various vibration devices. A sister operation to placing, compaction rates should be about equal to the time it takes to place. See placing and rodding.

Composite construction

Any element in which concrete and steel, other than reinforcing bars, work as a single structural unit. See rebar.

Compressive strength

The ability of a structural material to withstands squeezing forces. The maximum compressive stress which material, Portland cement, concrete, or grout is capable of sustaining.


Concrete is a hardened building material created by combining a mineral (which is usually sand, gravel, or crushed stone) a binding agent (natural or synthetic cement), chemical additives, and water. It is an excellent material to be used in road building, bridges, airports, factories, waterways and other construction projects. Concrete is the mixture of Portland cement, sand, gravel, and water used to make garage and basement floors, sidewalks, patios, foundation walls, etc. It is commonly reinforced with steel rods (rebar) or wire screening (mesh). See binder, cement, Portland cement, and rebar.

Concrete block

A concrete masonry unit, most often hollow, that is larger than a brick. See concrete masonry unit (CMU).

Concrete contraction

The shrinkage of concrete that occurs as it cures and dries. See shrinkage.

Concrete finish

A description of the smoothness, texture, or hardness of a concrete surface. Floors are trowelled with steel blades to compress the surface into a dense protective coat. See trowel, troweling, and trowel finish.

Concrete finishing machine

A portable machine with large paddles like fan blades used to float and finish concrete floors and slabs. A large power-driven machine mounted on wheels that ride on steel pavement forms. These machines are used to finish concrete pavements. See float and finishing.

Concrete masonry unit (CMU)

A block of hardened concrete, with or without hollow cores, designed to be laid in the same manner as a brick or stone. A CMU is also referred to as a concrete block. See concrete block.

Concrete mixture

The percentage of cement content contained in the concrete. A rich mixture contains a high proportion of cement. A lean mixture is a mixture of concrete or mortar with a relatively low cement content. A harsh mixture of concrete is one without mortar or aggregate fines, resulting in an undesirable consistency and workability. See aggregate, cement, cement content/cement factor, cement mixtures, cement types.

Concrete transporting

The process of moving the concrete mixture from the central plant, or mixing location, to the construction site. Transporting devices include agitator trucks, buckets, wheelbarrows, conveyors, and pumping devices. See agitator truck.

Connector bolts

(1) Fastening devices used to connect forms and forming accessories. The typical style is a slotted bolt with a locking wedge so concrete residue cannot form on standard bolt.

(2) Bolts designed with vertical slots used in conjunction with a small metal wedge to attach two flatwork forms together during stacking use. See flatwork forms, flexible forms, stacking, and straight forms.


The degree of plasticity of fresh concrete or mortar. The normal measure of consistency is slump for concrete and flow for mortar. See slump and slump test.


Compaction usually accomplished by vibration of newly placed concrete to minimum practical volume, to mold it within form shapes and around embedded parts and reinforcement, and to eliminate voids other than entrained air.

Construction joint

The contact between the placed concrete and concrete surfaces, against or upon which concrete is to be placed and to which new concrete is to adhere, that has become so rigid that the new concrete cannot be incorporated integrally by vibration with that previously placed. Unformed construction joints are placed horizontally or nearly horizontally.


A person or company licensed to perform certain types of construction activities that undertakes a legal obligation to perform specified construction work. Types of contractors include:

· General contractor - responsible for the execution, supervision and overall coordination of a project and may also perform some of the individual construction tasks. Most general contractors are not licensed to perform all specialty trades and must hire specialty contractors for such tasks, e.g. electrical, plumbing.

· Remodeling contractor - a general contractor who specializes in remodeling work.

· Specialty contractor - licensed to perform a specialty task e.g. electrical, side sewer, asbestos abatement.

· Sub contractor - a general or specialty contractor who works for another general contractor.

Control joint

Tooled, straight grooves made on concrete floors to "control" where the concrete should crack.

Corner forms

Metal concrete forms that are specialized forming accessories that are attached to straight forms to form 90° corners. Typical applications for corner forms include patios, sidewalks, warehouse floors, slab on grade house foundations, and similar flatwork applications. See slab on grade and straight forms.


Construction slang term to describe the cement and sand component of ready-mix that rises when the aggregate is worked down by way of agitation - floating, troweling, screeding, etc. This is also referred to as "juice". See float, floating, ready-mixed concrete, screed, screeding, trowel, and troweling.

Curb and gutter

The border area of a street, or other paved surface, that includes a curb, an extruded or hand-formed berm, and a gutter, the area designed to remove and transport water away from the main paved area. Both parts are usually made out of concrete. See curb and gutter combination and curb and gutter forms.

Curb and gutter accessories

Forming components, specialized tools, and attachments that are used to facilitate curb and gutter placement and include hangers, bracing, stake pullers, filler forms, form stakes, form pins, and curbface mules.

Curb and gutter combination

Refers to curbs and gutter combinations that are formed in the same concrete pour. The curb portion varies from 4" to 12" in height and is used to prevent vehicles from leaving a paved area. The gutter portion varies from 6" to 12" in width and is used to control water runoff from pavement. The elevation of the gutter is either slightly above, or slightly below, the grade of the pavement. Additionally, the gutter itself will have a slight inward or outward slant to direct the flow of water either towards or away from the curb, dependent on the desired water flow. See pouring, pitch-in, and pitch-out.

Curb and gutter face forms

Metal forms used in placing concrete that attach to the curb and gutter system to form the profile for the curbface.


Curb and gutter forms

Concrete forms and accessories used to pour a curb and gutter combination. The curb and gutter forming systems consists of a back form, a face form, a front form, a division plate and a top spreader. Back and front forms are standard straight forms with the back form taller than the front form for a curb and gutter combination configuration. See division plate, straight forms, and top spreader.

Curbface batter

Curbface batter refers to the distance between the top slope of a curbface and the bottom slope of a curbface. See batter.


Curbface mule

A mechanical tool used to form the desired curb profile for any curb and gutter application. See curb and gutter forms.

Curbface tool

A hand tool made to match the profile of the curbface used to finish and smooth the curbface after concrete placement, but before concrete hardening. See mule.

Curbface transition forms

Curbface transition forms allow a contractor to quickly change from a straight to a radius curb and back to a straight curb. They usually come in male/female pairs.


Method of maintaining sufficient internal humidity and proper temperature for freshly placed concrete to assure proper hydration of the cement, and proper hardening of the concrete. See hydration.


The hardening of concrete, plaster, or other wet material. Curing typically occurs through the evaporation of water or a solvent, hydration, polymerization, or chemical reactions of various types. It is the final process, after placing and compacting, that ensures the concrete will set to its desired strength. The length of time is dependent upon the type of cement, mix proportion, required strength, size and shape of the concrete section, weather and future exposure conditions. The period may be 3 weeks or longer for lean concrete mixtures used in structures such as dams or it may be only a few days for richer mixes. Favorable curing temperatures range from 50° to 70° F. Design strength is achieved in 28 days. See cement mixture, compaction, hydration, and set.

The American Concrete Institute defines curing as maintaining satisfactory moisture content and temperature in concrete during its early stages so that it may obtain the desired properties. See placing and compaction.

Curing blanket

A layer of straw, burlap, sawdust, or other suitable material placed over fresh concrete and moistened to help maintain humidity and temperature for proper hydration. See burlap, curing, curing compound, and curing membrane.

Curing compound

A chemical applied to the surface of fresh concrete to minimize the loss of moisture during the first stages of setting and hardening. See curing, curing membrane, and curing blanket.

Curing membrane

Any of several kinds of sheet material or spray-on coatings used to temporarily retard the evaporation of water from the exposed surface of fresh concrete, thus ensuring a proper cure. See burlap, curing, curing compound, and curing blanket.

Custom forms

A variety of unique forms used for specialized concrete forming such as reversible forms, super flat forms, tilt-up forms, tilt-up reversible forms, foundation set forms, seawall forms, rehab forms, and column forms.

Cut and fill

A term used to describe the addition or subtraction from a grade mark. Also, an operation commonly used in road building and other rock and earthmoving operations in which the material excavated and removed from one location is used as fill material at another location.


A process used on concrete, masonry or stone surfaces to repel water, the main purpose of which is to prevent the coated surface from absorbing rain water while still permitting moisture vapor to escape from the structure. (Moisture vapor readily penetrates coatings of this type.) "Dampproofing" generally applies to surfaces above grade; "waterproofing" generally applies to surfaces below grade.

Darby (derby, derby float, derby slicker)

A stiff straightedge of wood or metal used to level the surface of wet concrete. A portable machine with large paddles like fan blades used to float and finish concrete floors and slabs. A large power-driven machine mounted on wheels that ride on steel pavement forms and is used to finish concrete pavements. See screed and float.

Derated concrete

Concrete that has had a gas-forming chemical added to it so that when it sets it contains many air holes and is lightweight.


A material capable of holding finely ground particles in suspension. Used as a slurry thinner or grinding compound. See slurry.

Division plate

A concrete forming accessory used to create a break in a concrete sidewalk or curb and gutter. This engineered break minimizes the chances of the poured concrete cracking due to the surrounding ground shifting as a result of variety of factors including freezing, thawing, or heat expansion.

Division plate (full)

Full plates are used as bulkheads in the curb and gutter system and also are used to hold expansion material during concrete placement.

Division plate (punched for dowel)

Division plates punched for dowel are full division plates with slots punched on the bottom to accommodate the use of dowels or rebar. The punched slots hold the dowels or rebar in place during placement and prevents the material from floating in the placement. See dowel and rebar.

Division plate (skeleton)

Skeleton division plates are used to support the curbface form and add support for the curb and gutter system. See curb face form.

Division plate (slotted for rebar)

Also known as an S/B division plate. Division plates with slots for rebar provide the contractor with the ability to ensure the rebar will stay exactly where it is positioned into a curb and gutter placement, eliminating problems with the final rebar positioning.


The acronym for the Department of Transportation.


A cylindrical piece of stock inserted into holes in adjacent pieces of material to align and/or attach the two pieces. See rebar and reinforced concrete.

Dowel-bar reinforcement

Short sections of reinforcing steel that extend from one concrete placement into the next. They are used to increase strength in the joint. See dowel, rebar, and reinforced concrete.

Dowel lubricant

A lubricant applied to dowels placed in adjoining concrete slabs to allow longitudinal movement in expansion joints. See dowel, expansion joint, and rebar.

Dowel screw

A threaded dowel. See dowel.

Dry concrete

Concrete that has a low water content, making it relatively stiff. The effects are a lower water-cement ratio, less pressure on forms, lower heat of hydration, and a consistency that allows for placement on a sloping surface. See heat of hydration.

Dry pack

A low-slump grout tamped into the space in a connection between pre-cast concrete members. See slump and pre-cast concrete.

Dry shake (dry topping)

A concrete surface treatment, such as color, hardening, or antiskid, which is applied to a concrete slab by shaking on a dry, granular material before the concrete has set and then troweling it in. See shake-on hardener and troweling.

Drying shrinkage

Contraction caused by the loss of moisture, particularly in concrete, mortar, and plaster. See shrinkage.

Edger (edging trowel)

A tool used to fashion finishing edges or round corners on fresh concrete or plaster. See trowel, troweling, trowel finish.

Edging trowel

See edger.


The process by which water leeches soluble salts out of concrete or mortar and deposits them on the surface. Also used as the name for these deposits.


Able to return to its original form after the removal of stress.

Elastic shortening

The shortening of a member in pre-stressed concrete that occurs on the application of forces induced by pre-stressing. See pre-stressed concrete.

End plugs

Heavy-gauge metal cap ends for the straight steel forms.

Expansion joint

A surface divider joint that provides space for the surface to expand. It is usually composed of a fibrous material (~1/2" thick) and often installed in and around a concrete slab to permit it to move up and down (seasonally) along the non-moving foundation wall.

Expansive-cement concrete

A concrete made from expansive cement for the purpose of reducing or controlling volume changes that occur during curing. See curing.

Exposed aggregate

See Aggregate, exposed.

Exposed aggregate finish

A method of finishing concrete which washes the cement/sand mixture off the top layer of the aggregate - usually gravel. It is often used in driveways, patios and other exterior surfaces. See Aggregate, exposed.

Extension chute

An additional chute used by a concrete contractor to extend the length of the existing chutes from a ready-mix concrete truck. They are frequently used to pour floors. See agitator truck and ready-mixed concrete.

Extension pocket

Concrete forming accessories used to hold a form over a trench without adding additional supports underneath. This device consists of a stake pocket that is attached to an adjustable horizontal brace and then attaches to the stake pocket of the form. This device allows the forms to be set in areas that have been trenched by allowing the form bracing to "float" above and over the trench.

F numbers

The specification of the degree of flatness that a slab or floor must have. The degree of flatness of a concrete floor is extremely critical for warehouse or manufacturing plant floors where specialized materials handling equipment may be guided by wires under the concrete floor.

Face forms

Concrete forms that are used to create a desired curb profile. They attach to the curb and gutter form set up by hooking to the clips of the division plate. Face forms are designed based on the amount of batter specified. See batter, curb and gutter combination, and curb and gutter forms.

Faced concrete

To finish the front and all vertical sides of a concrete porch, step(s), or patio. Normally the "face" is broom finished. See broom finish.

Fair face concrete

A concrete surface that, on completion of the forming process, requires no additional (concrete) treatment other than curing. See architectural concrete and curing.

False set

The rapid development of rigidity in a mixed Portland cement paste, mortar, or concrete without the evolution of much heat. This rigidity can be dispelled and plasticity regained by further mixing without the addition of water. Premature stiffening, and rubber set are terms referring to the same phenomenon, but false set is the preferred term. See flash set, Portland cement, and set.


Material accumulating on a trowel during smoothing. Fat is used to fill in small imperfections. See trowel and troweling.

Fat mix / rich mix

A mortar or concrete mix with a relatively high cement content. Fat mix is more easily spread and worked than a mix with the minimum amount of cement required for strength. See cement and cement mixture.

Fiber reinforced concrete

A variant of concrete that is produced by adding fibers made of stainless steel, glass or carbon to the mixture. See reinforced concrete.

Fibrous admixture

Special fibrous substances of glass, steel, or polypropylene that are mixed into concrete to act as a reinforcement against plastic shrinkage cracking.

Filler forms

Concrete forming accessories used to connect two metal forms when a gap between the forms exists. Typically, filler forms have a channel that slides over the top rail of the forms to be connected. See straight forms.

Fine aggregate

Aggregate passing the 1/2" sieve and almost entirely passing the No. 4 sieve and predominantly retained on the No. 200 sieve.

Fineness modulus

An index of fineness or coarseness of an aggregate sample. An empirical factor determined by adding total percentages of an aggregate sample retained on each of a specified series of sieves, and dividing the sum by 100. Note: US Standard sieve sizes are used: No. 100, No.50, No. 30, No. 16, No. 8, and No. 4, and 3/8 inch, 3/4 inch, 1 inch, 2 inch, 3 inch, and 6 inch.


Leveling, smoothing, compacting, and otherwise treating surfaces of fresh or recently placed concrete or mortar to produce the desired appearance and service. See also float.

Fixed nose form

A metal concrete pouring form with a fixed nose piece to allow it to interlock with the rear section of another form creating a solid interconnection. Fixed nose forms must be removed in order or reverse order after a pour due to their interlocking nature. See sliding nose forms.

Flash set

The rapid development of rigidity in a mixed Portland cement paste, mortar or concrete usually 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 false set.

Flat stakes

Flat metal stakes used to secure wooden forms in sandy or loose soils prior to concrete placement. See curb and gutter forms, form pins, flatwork forms, and nail stakes.


Common word for concrete floors, driveways, basements, and sidewalks.

Flatwork forms

Metal or wood forms used in concrete flatwork placement. These forms are typically used for edge forming, sidewalks, driveways, footings, industrial slabs, foundations, patios, general flatwork, and in combination with our curb and gutter accessories, plus concrete curb and gutter work. See curb and gutter forms, flexible forms, and straight forms.

Flexible forms

Metal forms used forming radius shapes such as islands, serpentine sidewalks, curved curbs, parking lot turnouts, and similar applications. They are made from spring steel and are typically 10 feet long with stake pockets riveted onto the form every 18". They range in height form 4" to 12". The same as radius forms. See spring steel.

Flexible filler forms

A flatwork form accessory used to fill in spans of less than 10' where radius forming is required. These forms are sometimes referred to as rehab forms. See flatwork forms, flexible forms, and straight forms.


A tool (not a darby), usually of wood, aluminum, magnesium, rubber, or sponge, used in concrete or tile finishing operations to impart a relatively even but still open texture to an unformed fresh concrete surface. See darby and trowel.

Float coat

A finish coat of cement paste applied with a float. See float.


The next-to-last stage in concrete work, when you smooth off the job and bring water to the surface by using a hand float or bull float. The operation of finishing a fresh concrete or mortar surface by use of a float, preceding troweling when that is the final finish. See troweling, float, and float coat.

Floating wall

A non-bearing wall built on a concrete floor. It is constructed so that the bottom two horizontal plates can compress or pull apart if the concrete floor moves up or down. A floating wall is normally built on basements and garage slabs.


The section of a pitch-in curb where water flows in a parallel direction. See pitch-in.

Fly ash

A byproduct produced by coal-burning power plants that contains aluminosilicate and small amounts of lime. When combined with lime in a hydrothermal (using hot water under pressure) process, cement can be produced. It is a concrete admixture. See admixture.


The widened portion of the foundation or a structure that spreads and transmits the load from the building or foundation directly to, and across a broader area of, the soil. A continuous 8" or 10" thick concrete pad installed before that supports the foundation wall or monopost.


A temporary erected structure or mold for the support and containment of concrete during placement and while it is setting and gaining sufficient strength to be self-supporting.

See corner forms, formwork, filler forms, flexible forms, keyway forms, placement, radius forms, reversible forms, straight forms, slurry, tilt-up forms, tilt-up reversible forms, and transition forms.

Form hanger

A device used to support formwork from a structural framework. The dead load of forms, weight of concrete, and construction and impact must be supported. See formwork.

Form pins

Solid steel pins made from either cold-rolled and hot-rolled steel used for securing metal flatwork forms to the ground by driving the pins through wedge pockets and for attaching screed bar holder clamps used flatwork finishing.

Pins are typically 1/2" or 7/8" in diameter and vary in length from 12" to 48" or more depending on the project requirements.

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

Form rail

The top edge of a straight form that runs the length of the form and is typically 2 inches wide for most standard forms. Often, form rails are used as guides and supports for screeding. See screeding and straight forms.

Form release agent or compound

Material used to prevent bonding of concrete to a surface, such as to forms. See bond breaker, stripping agent, and release agent.

Form scabbing

The inadvertent removal of the surface of concrete as a result of adhesion to the form.

Form stakes

See form pins.


The use of metal or wood forms to create the proper placement of concrete. The forming process channels the concrete into the desired shape and thickness.

See corner forms, filler forms, flexible forms, keyway forms, placement, radius forms, reversible forms, straight forms, slurry, tilt-up forms, tilt-up reversible forms, and transition forms.


Temporary structures or forms made of wood, metal, or plastic used in the placing of concrete to ensure the slurry is shaped to its desired final form. Formwork must be strong enough to support the considerable weight and pressure of wet concrete without deflection.

See corner forms, filler forms, flexible forms, keyway forms, placement, radius forms, reversible forms, straight forms, slurry, tilt-up forms, tilt-up reversible forms, and transition forms.


The entire masonry substructure below the first floor or frame of a building, including the footing upon which the building rests.

Foundation form sets

Custom made sets of metal concrete forms used for houses, garage, car port, strip mall, warehouse floors, and other structures which require slab on grade foundations. See custom forms and foundation.

Foundation ties

Metal wires that hold the foundation wall panels and rebar in place during the concrete pour.

Foundation waterproofing

A high-quality below-grade moisture protection. It is used for below-grade exterior concrete and masonry wall damp-proofing to seal out moisture and prevent corrosion. Foundation waterproofing normally looks like black tar.


The setting up of formwork. See formwork.

General contractor

A contractor who enters into a contract with the owner of a project for the construction of the project and who takes full responsibility for its completion, although the contractor may enter into subcontracts with others for the performance of specific parts or phases of the project. See contractor.

Glass Fiber Reinforced Concrete (GFRC)

Material used in wall systems that resembles but generally does not perform as well as concrete. It usually is a thin cementitious material laminated to plywood or other lightweight backing.


The surface or level of the ground. The existing or proposed ground level or elevation on a building site or around a building. The slope or rate of incline or decline of a road, expressed as a percent. A designation of a subfloor, either above grade, on grade, or below grade. Any surface prepared to accept paving, conduit, or rails. See line.

Grade line

A strong string used to establish the top of a concrete placement.


A high-slump mixture of Portland cement, aggregates, and water which can be poured or pumped into cavities in concrete or masonry for the purpose of embedding reinforcing bars, and/or increasing the amount of load-bearing material in a wall. See aggregate, Portland cement, rebar, and slump.


A term sometimes used to designate dry-mix shotcrete. See shotcrete.

Hand float

A wooden tool used to lay on and to smooth or texture a finish coat of plaster or concrete. See float, trowel and darby.


A straight metal bar with pockets on an adjustable slide that allow straight forms to be placed in areas where securing forms into position is difficult due to soil conditions, existing pavement, or obstacles.

Hangers are often used in applications such as sidewalks, foundations, and curb and gutter work. See straight forms.


The curing agent of a two-part synthetic resin, adhesive, or similar coating. See curing.


An extension, a knee like protrusion of the foundation wall that a concrete porch or patio will rest upon for support.

Heat of hydration

The thermal energy, or heat, resulting from chemical reactions with water, as in the curing of Portland cement, concrete, or gypsum, as it cures. See concrete, curing, hot load, and Portland cement.

High chair

Slang for a heavy, wire, vaguely chair-shaped device used to hold steel reinforcement off the bottom of the slab during the placement of concrete. See bar chair and chair.

High-pressure steam curing (autoclave curing)

The steam curing of products made from cement, sand-lime, concrete, or hydrous calcium silicate in an autoclave at temperatures of 340° to 420° F.

Holding period

Period in the manufacture of concrete products, the period between completion of casting and the introduction of additional heat or the steam curing period.


A method by which concrete is poured and not puddled or vibrated, allowing the edges to have voids or holes after the forms are removed. An area in a foundation wall where the aggregate (gravel) is visible. Honeycombs can be usually be remedied by applying a thin layer of grout or other cement product over the affected area. See aggregate and vibration.

Hot load

Construction slang used to describe ready-mix concrete that has begun its hydration process while still in the delivery drum of the agitator truck. Hydration causes heat build up in the concrete mix. See ready-mixed concrete, hydration, heat of hydration, and agitator truck.

Hot-rolled solid steel form pins

Concrete forming metal pins that were formed by rollers from a hot plastic state into its final shape. Hot rolled pins are characterized by a rough, scaly surface and do not contain the tensile strength of cold-rolled steel pins. See cold-rolled solid steel form pins.


The chemical reaction that occurs when cement is mixed with water. See hot load and heat of hydration.

Hydraulic cement

A variety of cement engineered to harden under water. See air-entrained agent.

Initial set

A degree of stiffening of the cement and water mixture. This is a degree less than final set and is 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. See false set, flash set, and set.

Initial stress

In pre-stressed concrete, the stresses occurring in the pre-stressed members before any losses occur. See pre-stressed concrete.

Jacking equipment

The device used to stress the tendons in pre-stressed concrete. See pre-stressed concrete.


A grate tamper used to cause sand and cement grout to rise to the surface of wet concrete during placement of slabs. May be motorized or hand operated. See tamper.


Position where two or more building materials, components or assemblies are put together, fixed or united, with or without the use of extra jointing products. The location between the touching surfaces of two members or components joined and held together by nails, glue, cement, mortar, or other means.


Kelly ball

A device for determining the consistency of fresh concrete. It is sometimes used as an alternative to the slump test. See slump, slump cone, and slump test.


A slot formed into a concrete surface for the purpose of interlocking with a subsequent pour of concrete.


A recess or groove in one lift or placement of concrete that is filled with concrete of the next lift, giving shear strength to the joint. Also called a key.

Keyway attachments

A ten-foot long keystone-shaped metal concrete forming accessory that attaches to standard metal forms used to create horizontal tongue and groove connections for all types of floors and slabs. See flatwork forms and straight forms.

Keyway forms

Metal concrete forming devices used to pour interconnecting slabs. They are basically standard straight forms with holes drilled along the center face onto which a keyway is bolted and then used to pour "keyed" slabs. When the straight forms are needed for a standard pour, the keyway attachment is easily removed. See straight forms.


A furnace, oven, or heated enclosure for drying (wood), or charring, hardening, baking, calcining, sintering, or burning various materials. A furnace for firing clay or glass products or a heated chamber for seasoning wood.

Knee boards

Boards used by concrete finishers to kneel on to perform hand trowel flatwork. See trowel and troweling.


A residue of weak and non-durable material consisting of cement, aggregate, fines, or impurities brought to the surface of overwet concrete by the bleeding water. See bleeding.

Lateral force

A force acting in a generally horizontal direction, such as wind, earthquake, or soil pressure against a foundation wall.


A layer of concrete.

Lift-slab construction

A building method for multi-story sitecast concrete buildings that casts all the slabs in a stack on the ground and then lifts them up the columns and welds them into place. See sitecast concrete.


A rope or string made of nylon used as a guide to set forms to grade. See grade.

Lock clamps

Accessory clamps used to connect transition forms to flexible forms used in all flatwork and curb and gutter applications. See curb and gutter forms, flatwork forms, flexible forms, and transition forms.

Long float

A concrete finishing float designed to be handled by two men. See float.

Low-lift grouting

The common and simple method of unifying concrete masonry, in which the wall sections are built to a height of not more than 4" before the cells of the masonry units are filled with grout.


An aggregate used in heavy weight concrete, consisting primarily of ferrous metaferrite (Fe 304). A black magnetic iron ore with a specific gravity of approximately 5.2 and a Mohs hardness of about 6. See aggregate.


One who builds with brick, stones, concrete masonry units, or concrete. See concrete masonry units and concrete.


Construction composed of shaped or molded units, usually small enough to be handled by one man and composed of stone, ceramic brick, or tile, concrete, glass, adobe, or the like. The term masonry is sometimes used to designate cast-in-place concrete.

Masonry cement

A mill-mixed mortar to which sand and water must be added. A Portland cement with dry admixtures designed to increase the workability of the mortar. See Portland cement.

Mass concrete

Any volume of concrete with dimensions large enough to require that measures be taken to cope with generation of heat from hydration of the cement and attendant volume change, to minimize cracking. See heat of hydration.


The curing and hardening of construction materials such as concrete, plaster, and mortar. See curing.


A heavy mallet with an oversized wooden head used for driving wood takes, pegs, or wedges into the ground or in other applications where material might sustain damage if struck with a conventional sledgehammer. It is also referred to as a "beetle".

Maximum size aggregate

Aggregate whose largest particle size is present in sufficient quantity to affect the physical properties of concrete; generally designated by the sieve size on which the maximum amount permitted to be retained is 5 or 10 percent by weight.

Membrane curing

A process of controlling the curing of concrete by sealing in the moisture that would be lost to evaporation. The process is accomplished either by spraying a sealer on the surface or by covering the surface with a sheet film.


A general term referring to the combined ingredients of concrete or mortar. Examples might be a five-bag mix, a lean mix, or a 3,000-psi mix. See concrete mixture.


Equipment used for mixing or blending the materials used in the manufacture of concrete, grout, or mortar.

Mixing speed

Rate of mixer drum rotation or that of the paddles in a pan, open-top, or trough type mixer, when mixing a batch; expressed in revolutions per minute (rpm) or in peripheral feet per minute of a point on the circumference at maximum diameter.

Mixing time

For stationary mixers, mixing time is calculated in minutes from the completion of charging the mixer until the beginning of discharge. For a truck mixer, time is calculated in total minutes at a specified mixing speed. The period during which materials used in a batch of concrete are combined by the mixer.


A plain or reinforced mass of concrete cast as a single, one piece, integral structure.

Monolithic surface treatment

A concrete finish obtained by shaking a dry mixture of cement and sand on a concrete slab after strike-off, then troweling it into the surface. See strike off and troweling.


A mixture of cement (or lime) with sand and water used in masonry work.

Mortar board

A mason's hand tool used to hold small amounts of material that is typically being applied to a vertical surface with a hand trowel. It is often used in patching and finish work. The mortar board is a square flat piece of wood or metal with a handle placed in its center on the bottom side.


Slang term for cement or mortar.

Mud slab

A base slab of low-strength concrete from 2" to 6" thick placed over a wet subbase before placing a concrete footing or grade slab.


A hand-held or machine mounted device used to shape concrete by dragging or pressing it over the form boards. This device is commonly used in curb and gutter work. See curb and gutter.


The unacceptable occurrence when the top of a caisson concrete pier spreads out and hardens to become wider than the foundation wall thickness. See caisson.

Nail stakes

Round steel pins used to fasten wood forms together and securing them to the ground by pounding nails through pre-drilled holes in the pins.

They are commonly used in all flatwork applications and for attaching screed bar holder clamps in flatwork finishing. They typically are made in 1/2" or 7/8" diameters and come in lengths form 12" to 48".

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

Neat cement

Unhydrated hydraulic cement. See hydraulic cement.

Neat cement-paste

A mixture of water and hydraulic cement, both before and after setting and hardening. See hydraulic cement.

No-fines concrete

A concrete mixture in which only the coarse gradation (3/8" to 3/4" normally) of aggregate is used. See aggregate.

Non-agitating unit

A truck-mounted unit for transporting ready-mixed concrete short distances, but not equipped to provide agitation (slow mixing) during delivery. See agitator truck and ready-mixed concrete.

Non-air-entrained concrete

Concrete in which neither an air-entraining admixture nor air-entraining cement has been used. See also air-entrained agent, admixture, and air-entrained concrete.

Ottawa sand

Sand used as a standard in testing hydraulic cements by means of mortar test specimens. This type of sand is produced by processing silica rock particles obtained by hydraulic mining of the orthoquartzite situated in open-pit deposits near Ottawa, Illinois; naturally rounded grains of nearly pure quartz. See hydraulic cement.

Outside radius

The formed outside radius of a bend.


Excessive use of vibrators during placement of freshly mixed concrete, causing segregation and excessive bleeding. See bleeding and segregation.


Portland cement plaster applied over masonry to make it less permeable to water.

Particle-size distribution

Particle distribution of granular materials among various sizes; for concrete material normally designated as gradation. It is usually expressed in terms of cumulative percentages smaller or larger than each of a series of sieve openings or percentages between certain ranges of sieve openings.

Paver, paving

Materials, typically masonry, that are laid down to make a firm, even surface.

Paving forms

Heavy duty metal forms used in the placement of concrete for concrete roadways, commercial driveways, intersection entrance and exit ramps, and airport work. See apron.

Paving machine

A self-propelled piece of construction equipment that forms and finishes concrete simultaneously. See slip form.

Pea gravel

Portion of concrete aggregate passing the 1/2" sieve and retained on a No. 4 sieve.


A process in which thin flakes of matrix or mortar are broken away from the concrete surface. It is caused by adherence of surface mortar to forms as forms are removed, or to trowel or float in Portland cement plaster. See concrete, forming, float, trowel, and Portland cement.


The development of relatively small cavities in a concrete surface due to phenomena such as cavitation or corrosion.


The amount of angle or slope used in concrete flatwork to disperse water. See slope.


A curb and gutter profile designed to accept water into the flow-line of the gutter. It is also referred to as wet-curb. See flow-line and pitch-out.


A curb and gutter profile designed to direct water away form the curb. It is also known as a dry-curb or spill-out curb. See flow-line and pitch-in.


The process of placing and consolidating concrete. A quantity of concrete placed and finished during a continuous operation. Also, inappropriately referred to as pouring. See placing.


The physical insertion of the concrete mixture into the final location avoiding segregation of the mixture materials and compaction can be achieved. The deposition, distribution, and consolidation of freshly mixed concrete in the place where it is to harden. Also, inappropriately referred to as pouring. See compaction and placement.

Plain concrete

Concrete either without reinforcement, or reinforced only for shrinkage or temperature changes. See shrinkage.

Plant mix

A mixture of aggregate and asphalt cement or liquid asphalt, prepared in a central or traveling mechanical mixer. Any mixture produced at a mixing plant. See agitator truck, central plant, concrete transporting, and ready-mixed concrete.

Plastic consistency

Condition in which concrete, mortar, or cement paste will sustain deformation continuously in any direction without rupture.


Property of freshly mixed concrete, cement paste or mortar which determines its ease of molding or resistance to deformation.


An agent used to increase the fluidity of fresh cement with the same cement/water ratio improving the workability and placement of the cement. Same as a superplasticizer.


See stake pocket.


A thermoplastic widely used in sheet form for vapor retarders, moisture barriers, and temporary construction coverings. See Visqueen.

Portland cement

A special synthetic blend of limestone and clay used to make concrete which is generally believed to be stronger, more durable, and more consistent than concrete made from natural cement. Portland cement is made by mixing calcareous material, like limestone, with silica, alumina, and iron oxide-containing materials. These materials are burned together and the resulting product, or admixture, is ground up to form Portland cement. See cement and concrete.


A method of pre-stressing reinforced concrete in which tendons are tensioned after the concrete has hardened. See pre-tensioning.


To cast concrete. A pour is an increment of concrete casting carried out without interruption. See casting.

Power float

See rotary float.

Pozzolano (ASTM C 618)

A siliceous, or siliceous and aluminous material, which in itself possesses little or no cementitious value but will, in a finely divided form, such as a powder or liquid and in the presence of moisture, chemically react with calcium hydroxide at ordinary temperatures to form permanent, insoluble compounds possessing cementitious properties.

Pre-cast concrete

Concrete forms cast into permanent shapes using reusable forms at a plant, then transported as fully cured structural units to the actual construction job site. See cast-in-place concrete.

Pre-mixed concrete

The same as ready-mixed concrete.

Pre-placed aggregate

Coarse aggregate placed in a form, with Portland cement grout injected later. See aggregate and Portland cement.

Pre-placed concrete

Concrete manufactured by placing clean, graded coarse aggregate in a form and later injecting a Portland cement-sand grout under pressure, to fill the voids.

Pre-stressed concrete

Concrete that has already been subjected to compression increasing its ability to withstand tension and stress without the need for steel reinforcement. Concrete in which internal stresses of such magnitude and distribution are introduced that the tensile stresses resulting from the service loads are counteracted to a desired degree. In reinforced concrete, the pre-stress is commonly introduced by tensioning the tendons. See reinforced concrete.

Pre-stressed concrete wire

Steel wire with a very high tensile strength, used in pre-stressed concrete. The wire is initially stressed close to its tensile strength. Then some of this load is transferred to the concrete, by chemical bond or mechanical anchors, to compress the concrete. See pre-stressed concrete.


The compressing of concrete in a structural member by pouring the concrete for the member around stretched high-strength steel strands, curing the concrete, and releasing the external tensioning force on the strands. See posttensioning.


The selection of proportions of material for concrete to make the most economical use of available materials to manufacture concrete of the required strength, placeability, and durability.

Pump mix

Special concrete used in a concrete pump. Generally, the mix has smaller rock aggregate than regular concrete mix. See aggregate.

Punched for dowel forms

Metal concrete placement forms with dowel holes punched into them to hold either solid dowels or rebar to reinforce the concrete placement. See dowels, rebar, reinforced concrete, and paving forms.

Radius (steel) forms

Metal forms used forming radius shapes such as islands, serpentine sidewalks, curved curbs, parking lot turnouts, and similar applications. See flexible forms.

Reactive aggregate

Aggregate containing substances capable of reacting chemically with the products of solution or hydration of the Portland cement in concrete or mortar, under ordinary conditions of exposure, resulting in harmful expansion, cracking, or staining.

Ready-mixed concrete

Concrete that is batched or mixed at a central plant before it is delivered to a construction site and delivered ready for placement. It is also known as transit-mixed concrete since it is often transported in an agitator truck. See agitator truck.


The reinforcing bar-ribbed steel bars installed in foundation concrete walls, footers, and poured in place concrete structures designed to strengthen concrete. Rebar comes in various thickness' and strength grade. The term rebar is short for reinforcing bar.

Refractory concrete

Concrete having refractory properties, suitable for use at high temperatures. Calcium-aluminate cement and refractory aggregates are normally used for the manufacture of this product.

Rehab forms

Light-weight extend angle-iron-shaped metal forms, often 10' long with a 2' top rail and no bottom rail, used to replace sections of sidewalk without extensive excavation of surrounding soil. Rehab forms slip into place and are anchored into place with stakes after removal of the damaged concrete.

Reinforced concrete

Concrete reinforced by the addition of steel bars making it more able to tolerate tension and stress. See pre-stressed concrete.

Release agent

Material used to prevent bonding of concrete to a surface, such as to forms. See bond breaker, form release agent.


The addition of water and remixing of concrete which has started to stiffen. This is usually not allowed as it may affect the ultimate strength.

Reversible forms

A formed metal channel that is a combination of two sizes of straight forms. A 90° angle is formed which each leg having a different height. This type of form is used when a concrete contractor needs to pour two slabs of different heights. One side of the form might have a height of 10" and the other side might have a height of 14". This variation allows the one set of forms to be used to pour two different slabs. See straight forms.


Delayed vibration of concrete that has already been placed and consolidated. This is most effective when done at the latest time a running vibrator will sink of its own weight into the concrete and make it plastic and workable again.

Road base

An aggregate mixture of sand and stone. See aggregate.

Road forms

Heavy duty 3/16" or 1/4" metal paving forms capable of supporting large screed machines. The screed machines ride on the top rails of the paving forms to level the concrete.

Rock pocket

Area or portion of hardened concrete which is deficient in mortar and consisting primarily of coarse aggregate and open voids; caused by insufficient consolidation or separation during placement, or both; by leakage from form. See aggregate.

Rod (tamping)

A round, straight steel rod, 5/8" in diameter and approximately 24" in length, having the tamping end rounded into a hemispherical tip, with a tip diameter of 5/8".


Compaction of concrete or the like by means of a tamping rod. See compaction.


Producing a concrete curb by hand shaping or hand rolling the curb without the use of face forms. See face forms.

Rotary float (power float)

Motor-driven revolving blades that smooth, flatten, and compact the surface of concrete slabs or floor toppings. See screed, float, floating, trowel, and darby.


Decking over an area of concrete placement, usually of movable panels and supports, on which buggies of concrete travel to points of placement.


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.


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).


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.


The breaking away of a hardened concrete surface.


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.


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.


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.


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.


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.


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.


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.


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.


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


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.


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.


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.


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


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


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.


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.


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


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.


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.


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.


Removing the formwork from concrete. See formwork.

Stripping agent

See release agent.


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


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


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.


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.


An implement used to consolidate concrete or mortar in molds or forms. A hand-operated device for compacting flooring topping or other unformed concrete by impact from the dropped device in preparation for strike off and finishing. Contact surface often consists of a screen or a grid of bars to force coarse aggregates below the surface that prevents interference with floating or troweling. It is also know as a jitterbug. See troweling.


The addition of water to the cement mix whether at the batch plant, during transit, or at the jobsite to achieve the specified water to cement ratio. See cement mixture.

Temperature rise

The increase of temperature caused by absorption of heat or internal generation of heat, as by hydration of cement in concrete. See hydration and heat of hydration.

Temperature rise period

The time interval during which the temperature of a concrete product rises at a controlled rate to the desired maximum in autoclave or atmospheric-pressure steam curing.


A steel element such as a wire, cable, bar, rod, or strand used to impart pre-stress to concrete when the element is tensioned. See rebar.

Tensile strength

Maximum unit stress which a material is capable of resisting under axial tensile loading, based on the cross sectional area of the specimen before loading.


The gauge or depth of a material.

Tilt-up construction

A method of constructing concrete walls in which the wall panels are cast and cured flat on the floor slab or surrounding area and then tilted up into their final wall positions.

Tilt-up forms

Forms used in tilt-up construction. Forms that are placed on the ground and a flat horizontal slab is poured. When the slab is dry it is picked up with heavy equipment and lifted into place as a vertical wall. See tilt-up construction.

Tilt-up reversible forms

Specially engineered forms with two-sided formed metal channels used to pour horizontal concrete slabs that will later be tilted up to vertical and fastened in place and used as walls. Each side of the tilt-up form will have a different height so that two different wall thickness depths can be poured using the same set of forms.

Tilt-up wall

Cast concrete units which are preformed which, when cured, are tilted to their vertical position and secured by mechanical fasteners to prior erected structural steel. Tilt-up wall units may be pre-cast. See pre-cast concrete.

Top spreader

(1) A "U" shaped clip that fastens the curbface form to the back form in a curb and gutter application to hold the face form firmly in position during concrete placement.

(2) Concrete forming accessories used to secure a curbface form to the back form of the curb and gutter system, or to secure two forms running in parallel to form a stand-alone curb or knee wall. See curb face form, curb and gutter forms, and placement.

Transit-mixed concrete

Concrete mixed in a drum on the back of a truck as it is transported to the construction site. Also know as ready-mixed or pre-mixed concrete.

Transition forms

(1) Metal or wood sections used to change from straight to flexible forming, or vice versa. They are typically used in all flatwork and curb and gutter applications.

(2) A concrete forming accessory used to connect flexible and straight forms. Small lock clamps are used to connect the flexible form to the transition form. See flatwork forms, flexible forms, straight forms.


A tube with removable sections and a funnel at the top used in concrete application. The bottom is kept beneath the surface of the concrete and raised as the form is filled and is used to pour concrete underwater. See hydraulic cement.


A thin, flat steel tool, either pointed or rectangular, provided with a handle and held in the hand, used to manipulate concrete, mastic, or mortar create a dense, smooth finish on a concrete surface. It is also a machine whose rotating blades are used to finish concrete slabs. See screed, float, bull float, and darby.

Trowel finish

The smooth finish surface produced by troweling. See trowel and troweling.


Smoothing and compacting the unformed surface of fresh concrete by strokes of a trowel. See trowel and trowel finish.

Truck mixer

A concrete mixer capable of mixing concrete in transit when mounted on a truck chassis. See agitator truck.

Truckload or Trailerload

A quantity of commodities weighing as much as 44,000 pounds, that is the standard weight limit on

Unbonded construction

Posttensioned concrete construction in which the tendons are not grouted to the surrounding concrete. See posttensioning and grout.

Unit water content

The quantity of water per unit volume of freshly mixed concrete, often expressed as gallons or pounds per cubic yard. This is the quantity of water on which the water cement ratio is based, and does not include water absorbed by the aggregate. See cement mixture.

Unreinforced concrete

Concrete made without steel reinforcing bars. See reinforced concrete and rebar.

U.S. highways.


An aggregate somewhat similar to perlite that is used as an aggregate in lightweight roof decks and deck fills. It is formed from mica, a hydrous silicate with the ability of expanding on heating to form lightweight material with insulation quality. Used as bulk insulation and also as aggregate in insulating and acoustical plaster and in insulating concrete. See aggregate.

Vibrating screed

A machine designed to act as a vibrator while leveling freshly placed concrete. See screed.


Energetic agitation of freshly mixed concrete during placement by mechanical devices, either pneumatic or electric, that create vibratory impulses of moderately high frequency that assist in evenly distributing and consolidating the concrete in the formwork. See compaction.

Vicat apparatus

A penetration device used to determine the setting characteristics of hydraulic cements. See hydraulic cement.


A 4 mil or 6 mil plastic sheeting often used for construction coverings. See Polyethylene, burlap, and curing blanket.

Wagner fineness

The fineness of materials such as Portland cement expressed as total surface area in centimeters per gram as determined by the Wagner turbidimeter apparatus and procedure. See Portland cement.


Horizontal bracing used to support or stiffen concrete forming. See forming.


A term used to describe a hand-held finishing tool that has been modified with extension handles so it can be used while standing up.

Warehouse set

The partial hydration of cement stored for a time and exposed to atmospheric moisture, or mechanical compaction occurring during storage. A partially hardened, unopened bag of cement. See hydration.

Water-cement ratio

A numerical index of the relative proportions of water and cement in a concrete mixture. The ratio of the amount of water, exclusive only of that absorbed by the aggregates, to the amount of cement in a concrete or mortar mixture. The ratio is preferably stated as a decimal by weight. For example, the ratio 1:2:4 refers to a mix which consists of 1 cubic foot of cement, 2 cubic feet of sand and 4 cubic feet of gravel. Cement and water are the two chemically active elements in concrete and when combined, form a paste or glue which coats and surrounds the particles of aggregate and upon hardening binds the entire mass together.

Water gain

See bleeding.

Water-reducing agents

A material that either increases workability of freshly mixed mortar or concrete without increasing water content, or maintains workability with a reduced amount of water; the effect being due to factors other than air entrainment.

Water repellant coating

Transparent coating or sealer applied to the surface of concrete and masonry surfaces to repel water.

Water stop

A synthetic rubber strip used to seal joints in concrete foundations walls.

Water table

The location of the underground water. Also, the vertical distance from the surface of the earth to this underground water.

Weep screed

A tool used to drain moisture from concrete.

Wet screeds

Concrete strips placed beforehand at the proper elevation to act as height guides when pouring a concrete slab. See pouring and slab.

Wetting agent

A substance capable of lowering the surface tension of liquids, facilitating the wetting of solid surfaces and permitting the penetration of liquids into the capillaries.

Wood forming accessories

A variety of miscellaneous accessories needed to work with wood forming when placing concrete. Typical accessories include corner forms, curb face forms, division plates, filler forms, form bracing, nail stake and form pin pockets, transition forms, form spreaders, and hangers.

See bracing, curb and gutter forms, flatwork forms, flexible forms, division plates, nail stakes, stake pockets, and transition forms.

Wood forms

Pieces of lumber, often 2x4s, used as single use or minimal use forms for concrete placement. See flatwork forms and straight forms.

Yard (of concrete)

One cubic yard of concrete is 3' x 3' x 3' in volume, or 27 cubic feet. One cubic yard of concrete will pour 80 square feet of 3.5' sidewalk or basement/garage floor.


The volume of freshly mixed concrete produced from a known quantity of ingredients. The total weight of ingredients divided by the unit weight of the freshly mixed concrete. The number of product units, such as block, produced per bag of cement or per batch of concrete.

Zero slump concrete

A concrete mixture with so little water that it has a slump of zero. See slump and slump test.

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