Additives -- Certain chemicals have been developed over the years to alter the properties of concrete and these are added during the mixing process. In freezing weather, a
chemical can be added to lower the freeze point of the wet mixture. In hot weather
and long distance hauling, crushed ice is sometimes added to the mixture to extend
time before the concrete begins to set. Fly ash costs less than cement and can be
substituted up to about 10 percent. Concrete is sometimes colored with dyes. Forms
are often sprayed with chemicals to prevent concrete from bonding to them.
Chemicals are available to increase the workability of concrete or to advance the
setting.

Aggregates -- A variety of graded materials that are components of concrete. Sand, gravel, or crushed stone are typical aggregates. A typical mix of concrete would contain
aggregates of two are more sizes one of which is always sand followed by one or more
sizes of rock or crushed stone.

Cement -- Finely ground calcined rock and clay materials that form the binder in concrete. Portland cement weighs about 97 pounds per cubic foot.

Chairs -- Plastic shapes used to support reinforcing steel prior to placement of concrete.

Concrete -- Mixture of cement, aggregates and water that will harden or set into a solid
stone-like material.

Concrete Plant -- Portable or fixed machinery that measures components of concrete and
places them in a mixer truck or is mixed on site for transport.

Cure Time -- The time for fresh concrete to reach its design strength. Typically concrete will reach 90 percent of design strength about 30 days after placing and gradually approach 100 percent over time. A recent development is HES or High Early Strength
concrete. Chemical additives like HES make it possible to use certain concrete
structures after only a few hours of curing.

Fly Ash -- By-product of smoke stack emission control that may be used as a substitute for a portion of the cement in a concrete mix.

Form -- A mold in which concrete is placed to set. These may be made of used wood materials, plastics, metal, etc. Some are disposable and other reusable. Can be self-constructed, purchased, or rented.

Hod -- Small platform, tray or trough that has a pole handle and that is borne on the shoulder for carrying loads as mortar or brick.

Hod Carrier -- A laborer employed in carrying supplies to bricklayers, stonemasons, cement finishers, or plasterers on the job.

Kiln -- Oven where high temperatures are used to fire bricks or other ceramic products.

Light Weight Concrete -- Special low density concrete used where strength is not a primary requirement.

Masons -- Generic term given to a broad class of skilled workers who make final placement of shaped masonry products and concrete.

Mortar Mix -- A special type of cement used as a component in the laying of bricks or blocks.

Portland -- Generic name given cement for general purpose concrete. First used by a 19th century developer of concrete. Named for a type of stone found in the British Islands.

Post-stressed -- A technique used mainly in the forming of foundation slabs where threaded steel rods are embedded in the concrete but transverse tension is not placed on the concrete until after the concrete is cured.

Pre-stressed -- A technique of embedding steel in concrete shapes so that the end result will meet certain design specifications for strength and rigidity.

Pumper --Equipment that is often truck mounted used to pump concrete from one place/level to another.

Rebars -- Steel rods ranging from 3/8- to 3-inches thick placed in concrete forms to produce reinforced concrete.

Reinforced Concrete -- Shapes containing steel bars or wire to create stronger and more shock resistant material.

Slump -- A field test given to concrete before curing that measures the viscosity and indirectly the water content. Generally the less viscous, the higher the cured strength for any given mix.

Strength -- Concrete strength is usually expressed in terms of pounds per square inch (PSI). 3,000 PSI is a typical specification for building foundations. A sample of wet concrete is placed in a test cylinder and after curing, the sample is compressed to its breaking point on a machine built to show a reading when the concrete breaks. Sometimes a sample is cut from the cured concrete with a circular cylinder cutter. An older and less precise measurement of strength is given in terms of "sacks" per yard. In other words a five bag mix would contain about 500 pounds of cement per cubic yard of concrete.
Tie Wire -- Short pieces of wire used to secure rebars in place until the concrete has been poured and at least partially cured.

Transit Mix -- Concrete that is mixed while being transported by truck to a job site.

Wall Ties -- Small strips of metal fastened to a building's primary structure to hold the masonry in place.

Source:
Department of the Treasury
Internal Revenue Service Training 3147-122 (8-98)
TPDS No. 85385S