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gravel,particles of rock, i.e., stones and pebbles, usually round in form and intermediate in size between sand grains and boulders. Gravel is composed of various kinds of rock, the most common constituent being the mineral quartz. Deposits of gravel are formed as a result of the weathering of rocks and the erosive and concentrating action of rivers and waves. Sometimes gravel becomes consolidated into the sedimentary rock called conglomerate. Gravel is used extensively in building roads and in making concrete. For road building it is crushed into angular particles of uniform size. One or more layers of gravel underlie the road surface. A small percentage of clay must be present to act as a binder when gravel is used in macadam for road surfaces. When used as a coarse aggregate for concreteconcrete,
structural masonry material made by mixing broken stone or gravel with sand, cement, and water and allowing the mixture to harden into a solid mass. The cement is the chemically active element, or matrix; the sand and stone are the inert elements, or aggregate.
..... Click the link for more information. , gravel must be clean and free from clay and organic matter. Commercially, it is classified according to the size of the particles. In areas where natural deposits are inadequate, gravel is produced by quarrying and crushing durable rocks, such as sandstone, limestone, or basalt.
a loose conglomeration of pebbles. Cemented gravel is one type of conglomerate. According to the petro-graphical composition of the pebbles, gravel may be classified as polymictal (pebbles of different composition), oligomictal (pebbles of two or three rocks), or monomictal (homogenous pebbles). The petrographical composition, shape, arrangement, and location of pebbles in a pebble incline determine the genetic type of gravel and establish the position of material in eroded places as well as the direction in which it has been washed out. Gravel is used as a construction material, generally in road building.
loose rock consisting of more or less rounded rock fragments and (less frequently) various minerals with a diameter of 1–10 mm (2–20 mm, according to other information). Gravel may be classified by size as fine (1–2.5 mm), medium (2.5–5mm) and coarse (5–10 mm). It is classified by origin as fluvial, lacustrine, marine, and glacial. Gravel is used as a construction material, a coarse concrete aggregate, and a road-building material. Cemented gravel is called grit.