CEMENT DICTIONARY OF TERMS Like every other branch of human activity, the concrete industry has developed a list of terms of special meaning. With the usage of these terms, the more common of which are given below, the student of cement and concrete should at the very outset make himself thor oughly familiar.
Activity—Manifestation of characteristic prop erties; the property of cement which causes it to set by undergoing chemical change on the addition of water.
Aggregates—The solid and relatively coarse in gredients which are bound together by ce ment in a mass of concrete. In the great ma jority of cases, the materials used as aggre gates are mineral, comprising sand, gravel, crushed stone, furnace slag, cinders, etc., of varying degrees of fineness. In the form of concrete known as "pulp concrete," saw dust, an organic material, is used as an ag gregate.
Chemically the aggregates are absolutely inert or inactive in the formation of concrete, playing only a physical part because of their presence as space fillers. Sand or other ma terial fine enough to pass through a sieve of one-fourth-inch mesh, was formerly not classed as an "aggregate," this term being confined to the coarser grades of material. Inasmuch, however, as the function of the 27 sand is essentially the same, both physically and chemically, as that of the coarser ingre dients, the later approved practice has come to include sand also among the "aggre gates." The word is of Latin origin—from "ad" (to) and "grex" (a flock)—and means things collected together in a mass.
Angularity—The property of having edges or faces that meet sharply at angles, as distin guished from shapes that are oval or rounded.
Argillaceous—Consisting of, or containing, clay.
Armored Concrete—Same as Reinforced Con crete.
Artificial Stone—A term applied to concrete be cause of its resemblance in appearance to natural stone and its similar use as • a mate rial of construction; any stone made by mix ing aggregates with adhesive material, al lowed to harden, and used instead of natural stone.
Calcareous—Consisting of, or containing, cal cium carbonate or carbonate of lime.
Calcining—Burning; subjecting to sufficient heat to cause partial chemical disintegration, or incipient or total fusion or vitrification.
Cement—The binding material which holds the aggregates together in concrete in a solid mass. Derived from Latin "caedere" (to cut), and signifies any substance used for making bodies adhere to each other, or bind ing together those which have been cut or broken apart, as mortar, glue, etc. The term was originally applied to rough, unhewn blocks of stone used in construction; later, to marble chips used in making mortar; later, to mortar itself; and was finally extended to include any sort of plastic bonding material.
Center—A middle point, line, or plane, used, for example, in measuring the distance from one joist, beam, or column to another; the tempo rary wooden or metal supports used in the erection of arches or other superimposed or overlying constructive work.
Core—The mould used to form the hollowed-out part of a cement or concrete block.
Empirical—Based on practical experience as distinguished from refined scientific and theoretical calculations. Empirical rules, for example, are founded merely on the observed results of actual experience, while the theory underlying such rules may never yet have been formulated.