Asphalt concrete

Asphalt concrete (commonly called asphalt, blacktop, or pavement in North America, and tarmac, bitmac or bitumen macadam in the United Kingdom and the Republic of Ireland) is a composite material commonly used to surface roads, parking lots, airports, and the core of embankment dams. Asphalt mixtures have been used in pavement construction since the nineteenth century. It consists of mineral aggregate bound together with bitumen (a substance also independently known as asphalt, pitch, or tar), laid in layers, and compacted.

The American English terms asphalt (or asphaltic) concrete, bituminous asphalt concrete, and bituminous mixture are typically used only in engineering and construction documents, which define concrete as any composite material composed of mineral aggregate adhered with a binder. The abbreviation, AC, is sometimes used for asphalt concrete but can also denote asphalt content or asphalt cement, referring to the liquid asphalt portion of the composite material.

Natural asphalt (Ancient Greek: ἄσφαλτος (ásphaltos)) has been known of and used since antiquity, in Mesopotamia, Phoenicia, Egypt, Babylon, Greece, Carthage, and Rome, to waterproof temple baths, reservoirs, aqueducts, tunnels, and moats, as a masonry mortar, to cork vessels, and surface roads.

The Procession Street of Babylonian King Nabopolassar, c. 625 BC, leading north from his palace through the city's wall, was described as being constructed from burnt brick and asphalt.

Natural asphalt covered and bonded cobbles were used from 1824 in France as a means to construct roads, as were moulded asphalt cobbles or blocks, formed from rammed natural rock asphalt.

In 1829 natural Seyssel asphalt mixed with 7% aggregate, to create an asphat-mastic surface, was used for a footpath at Pont Morand, Lyon, France, the technique spreading to Paris in 1835, London, England, in 1836, and Philadelphia, United States, in 1838.

In 1834, John Henry Cassell & Company of Poplar, London, a pitch and varnish supplier, obtained an English patent for a method to surface roads with a layer of tar, covered by a layer of macadam, and sealed with a layer of tar and sand, and marketed the surface "lava stone for paving and waterproofing"; soon after being contracted to surface the approach road to Vauxhall bridge, and a road in Millwall, London.

In 1837, Richard Tappin Claridge obtained a similar English patent (GB patent 1837 #7849), substituting Seyssel asphalt as the binder, having seen it employed in France and Belgium; he would subsequently form the Claridge's Patent Asphalte Company, in 1838.