Mixing is generally performed with the aggregate at about 150 ☌ (300 ☏) for virgin asphalt and 170 ☌ (330 ☏) for polymer modified asphalt, and the asphalt cement at 93 ☌ (200 ☏). Mixing of asphalt and aggregate is accomplished in one of several ways: Hot-mix asphalt concrete (commonly abbreviated as HMA) This is produced by heating the asphalt binder to decrease its viscosity and drying the aggregate to remove moisture from it prior to mixing. Mixture formulations As shown in this cross-section, many older roadways are smoothed by applying a thin layer of asphalt concrete to the existing portland cement concrete, creating a composite pavement. 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. The 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 process was refined and enhanced by Belgian-American inventor Edward De Smedt. It consists of mineral aggregate bound together with bitumen (also known as asphalt), laid in layers, and compacted. Asphalt mixtures have been used in pavement construction since the beginning of the twentieth century. Asphalt batch mix plant A machine laying asphalt concrete, fed from a dump truckĪsphalt concrete (commonly called asphalt, blacktop, or pavement in North America, and tarmac 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. For other uses, see Blacktop (disambiguation).
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