pavement

pavement, the wearing surface of a road, street, or sidewalk. Parts of Babylon and Troy are believed to have been paved; Roman roads were noted for their durable stone paving. Cobblestones were common from late medieval times into the 19th cent. A pavement known as macadam road, introduced in England in the 19th cent., is still used today; it consists basically of compacted layers of small stones cemented into a hard surface by means of stone dust and water (water-bound macadam). However, the main pavement surfaces in use today are bituminous/asphalt coverings and concrete. Desirable qualities in pavements include durability, smoothness, quietness, ease of cleaning, and a nonslippery surface. The requirements conflict to a degree, so no one material is ideal in all respects. The foundation of a pavement must be crowned, or slightly arched, for rapid shedding of water; it must be strong enough to withstand heavy dynamic loads, but capable of responding to temperature changes. In the bituminous macadam pavement, the foundation is macadam, upon which a bituminous material that penetrates at least 2 in (5 cm) into the foundation is poured, forming an impervious binder. In the bituminous-mixed macadam pavement, a mixture of crushed rock, ground glass and other additives, and bituminous binder is spread over a macadam foundation and rolled into a compact mass. The two other pavement types use a concrete road slab as a foundation. In the sheet asphalt pavement, a binder course and a wearing course are laid over a concrete foundation. The binder course, whose function is to prevent creepage of the upper course, is composed of broken stone and asphalt cement. The wearing surface is a mixture of fine sand, filler, and asphalt. By far the most common type of pavement for heavy use is rigid concrete. The first concrete pavement was laid in Bellefontaine, Ohio, in 1894. A modern highway will have a 6 in (15 cm) base of concrete, on top of which 3 in (7.5 cm) of steel-reinforced concrete will be laid. Pavements that must withstand only pedestrian traffic may use brick or wood-blocks, set in a 1 in. (2.5 cm) bedding of sand, cement mortar, or mastic. For ornamental pavements, see mosaic ; tile.

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pavement

Durable surfacing of a road, path, court, patio, plaza, airstrip, or other such area. The Romans, the greatest road builders of the ancient world, built their roads of stone and concrete. By AD 75 several methods of road construction were known in India, including brick and stone slab pavements, and street paving was common in towns. Smaller cobblestones began to be used for European paving in the late Middle Ages. The 18th–19th century saw the development of pavement systems (e.g., macadam) that used light road surfaces of broken or crushed stone. Modern flexible pavements contain sand and gravel or crushed stone compacted with a bituminous binder (e.g., asphalt or tar); such a pavement has enough plasticity to absorb shock. Rigid pavements are made of concrete, composed of coarse and fine aggregate and portland cement, and usually reinforced with steel rod or mesh.

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pavement

1. a hard-surfaced path for pedestrians alongside and a little higher than a road

2. a paved surface, esp one that is a thoroughfare

3. the material used in paving

4. Civil engineering the hard layered structure that forms a road carriageway, airfield runway, vehicle park, or other paved areas

5. Geology a level area of exposed rock resembling a paved road

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Pavement

An artificial surface laid over the ground to facilitate travel. A pavement's ability to support loads depends primarily upon the magnitude of the load, how often it is applied, the supporting power of the soil underneath, and the type and thickness of the pavement structure. Before the necessary thickness of a pavement can be calculated, the volume, type, and weight of the traffic (the traffic load) and the physical characteristics of the underlying soil must be determined.

Once the grading operation has been completed and the subgrade compacted, construction of the pavement can begin. Pavements are either flexible or rigid. Flexible pavements, which are composed of aggregate (sand, gravel, or crushed stone) and bituminous material (see illustration), have less resistance to bending than do rigid pavements, which are made of concrete. Both types can be designed to withstand heavy traffic. Selection of the type of pavement depends, among other things, upon (1) estimated construction costs; (2) experience of the highway agency doing the work with each of the two types; (3) availability of contractors experienced in building each type; (4) anticipated yearly maintenance costs; and (5) experience of the owner in maintenance of each type. See Concrete, Highway engineering