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Term Definition
Abutment Joint

A surface divider joint designed to allow free movement between new and existing construction or between different materials.


A substance, such as calcium chloride, added to a concrete mix to speed up its setting and strength development.

Access Flooring

A raised finish floor surface consisting entirely of small, individually removable panels beneath which wiring, ductwork, and other services may be installed.

Acoustical Ceiling

A ceiling of fibrous tiles that are highly absorbent of sound energy.


Science dealing with the production, control, transmission, reception and effects of sound, and the process of hearing.

Active Pressure

The pressure exerted by retained earth against a retaining wall.


A prepared substance added to concrete to alter or achieve certain characteristics.


Sand, gravel, crushed stone or other material that is a main constituent of Portland Cement, concrete and aggregated gypsum plaster. Also, polystyrene, perlite and vermiculite particles used in texture finishes.


American Insurance Assn., successor to the National Board of Fire Underwriters and a nonprofit organization of insurance companies. Also, American Institute of Architects.

Air Entrainment

The incorporation of tiny air bubbles into concrete or mortar to improve its workability and resistance to freezing.

Air-Supported Structure

A membrane enclosing a pressurized occupied space, which must be held down to its foundation.

Airborne Sound

Sound traveling through the medium of air.

Allowable Stress

The maximum unit stress permissible in a structural member. Also referred to as working stress.


Metal securing device embedded or driven into masonry, concrete, steel or wood.

Anchor Bolt

Heavy, threaded bolt embedded in the foundation to secure sill to foundation wall or bottom plate of exterior wall to concrete floor slab.