Absorbed Moisture Moisture that is held in a material.  In aggregates, the water which is not available to become part of the mixing water is known as "absorbed" water

Accelerator An admixture which, when added to concrete, increases the rate of hydration of the cement, shortens the time of set and increases the rate of hardening and strength development. This allows you to strip forms or use a floor sooner

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. This helps to maintain quality.

Admixture A material other than water, aggregates, and Portland cement that is used as an ingredient of concrete, and is added to the batch immediately before or during the mixing operation. These admixtures are often referred to as plasticizers, superplasticizers, accelerators, dispersants, and water-reducing agents.

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

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

Air Entraining Agent An addition for cement, or an admixture for concrete which entrains air in the form of minute bubbles in the concrete or mortar during mixing that increase its workability and aid in freeze thaw protection.

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.

Apron A slab of concrete extending beyond the entrance to a building, particularly at an entrance for vehicular traffic.

Architectural Concrete Concrete that will be permanently exposed to view and therefore requires special attention to appearance. This type of concrete is frequently cast in a mold and has a pattern on the surface.

Bag A quantity of Portland cement; 94 pounds in the United States. Different weights per bag are commonly used for other types of cement. Same as sack.

Base Coarse / Base A layer of material of specified thickness constructed on the subgrade of a pavement to serve one or more functions, such as distributing loads, providing drainage, or minimizing frost action.

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

Blowout Term used when the ready-mixed concrete breaks through the forms due to insufficient bracing.

Bull Float A board of wood or aluminum 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.

Caisson 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 lengths of 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 rock or satisfactory soil.

Cement Mixtures Mixtures are always listed as parts cement to Sand to Aggregate.

• Rich - 1 part cement, 2 parts sand, 3 parts coarse aggregate.
  Rich mix is used for concrete roads and waterproof structures.
• Standard - 1 part cement, 2 parts sand, 4 parts coarse aggregate.
  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.
  Medium mix is used for foundations, walls, abutments, piers, etc.
• Lean - 1 part cement, 3 parts sand, 6 parts coarse aggregate.
  Lean mix is used for all mass concrete work, large foundations, backing for stone masonry, etc

Cement, Portland (ASTM C150) Portland cement is the type of concrete that is typically used and also the same kind that you buy in a bag. A powdery substance made by burning at a high temperature a mixture of clay and limestone which produces lumps that are ground into a fine powder consisting of hydraulic calcium silicates

Cement types

• Type I Normal - is 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 groundwaters 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 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

Cementitious Having cement-like, cementing, or bonding type properties. Material or substance producing bonding properties or cement-like materials. Often used in fireproofing steel beams.

Coarse Aggregate Naturally occurring, processed or manufactured stone particles in prescribed gradation or size range, the smallest size of which will be retained on the No. 4 (4.76 mm) sieve

Compaction The elimination of voids in construction materials, as in concrete, plaster, or soil, by vibration or tamping. Prevents “bubbles” and other imperfections.

Compressive Strength The measured resistance of a concrete or mortar specimen to loading in pounds per square inch {psi) The maximum compressive stress which Portland cement or concrete capable of withstanding.

Concrete A building material which consists of a binding medium, within which are embedded particles or fragments of a relative inert filler in Portland cement concrete, the binder is a mixture of Portland cement, possibly additional cementitious materials such as fly ash, slag, and water; the filler may be any of a wide variety of natural or artificial, fine and coarse aggregates; and finally admixtures, if so desired.

Concrete Finishing Machine A machine which looks similar to a fan which is used to finish the surface of flat concrete work.

Curing The hardening of concrete. Curing 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. 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 time to fully cure 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.

Dispersing Agent An admixture that increases the fluidity of concretes by reduction of interparticle attraction.