| Task set - | (Software Engineering) a collection fo software engineering tasks that are required to complete an activity or action that is part of a software process framework |
| User - | (Software Engineering) the person who actually used to software or the product that has software embedded within it |
| User hierarchy - | (Software Engineering) a hierarchical representation of the categories of users that will interact with any type of software |
| AAC - Autoclaved Aerated Concrete | (Concrete Engineering) Exceptionally lightweight precast concrete with high thermal qualities and fire resistence. Suitable for cutting with ordinary hand tools. Mix design is composed of portland cement, sand or siliceous material, lime, gypsum, finely powdered aluminum, and water. Initial mix is a combination of portland cement, sand, lime and gypsum to produce a slurry. Finely powdered aluminum mixed into a paste is added prior to placement into large, rail-like forms. The finely powdered aluminum reacts with the alkaline components of the cement and lime to produce hydrogen gas, which increases the volume approximately five times producing a uniformly, dispersed cellular structure. Units are cut to required shape. Units are placed in an autoclave, an enclosed pressurized chamber, and steam cured at 3500 F. Approximately 80% of the ultimate volume consists of air voids. |
| Absorbed Moisture | (Concrete Engineering) Moisture which is mechanically held in a material. In aggregates, that water which is not available to become part of the mixing water is designated "absorbed" water. |
| Air Content | (Concrete Engineering) 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. |
| Blast Furnace Slag | (Concrete Engineering) A non-metallic waste product developed in the manufacture of pig iron, consisting basically of a mixture of lime, silica and alumina, the same oxides that make up portland cement, but not in the same proportions or forms. It is used both in the manufacture of portland blast furnace slag cement and as an aggregate for lightweight concrete. |
| Calcareous | (Concrete Engineering) Containing calcium carbonate or, less generally, containing the element calcium. |
| Calcium Aluminate Cement | (Concrete Engineering) The product obtained by pulverizing clinker consisting essentially of hydraulic calcium aluminates resulting from fusing or sintering a suitable proportioned mixture of aluminous and calcareous materials. |
| Capillarity | (Concrete Engineering) A wick-like action whereby a liquid will migrate vertically through material, in a upward direction; as oil in a lamp travels upward through the wick, |