Asfalt

Asfalt, commonly translated as asphalt, is a viscous binder combined with mineral aggregates to form asphalt concrete, the standard material for road surfaces. The binder is usually bitumen, a viscous petroleum product, while aggregates provide structure and skid resistance.

Asphalt concrete typically contains 4–7% binder by weight, with the remainder comprising aggregates and additives. Variants include polymer-modified bitumen to improve performance and asphalt emulsions used for cold or low-temperature applications.

Hot-mix asphalt (HMA) is produced in plants by heating aggregates and blending with hot bitumen, then laid and compacted while hot. Warm-mix asphalt lowers processing temperatures with additives. Cold-mix applications use emulsified asphalt that does not require heating.

Primarily used for roads, highways, airport runways, and parking surfaces, asphalt pavements are designed in layers: subgrade, subbase, base layers, and the wearing course. Design varies with traffic, climate, and drainage.

Maintenance includes crack sealing, resurfacing, and overlays. Reclaimed asphalt pavement (RAP) can be processed and re-used, reducing energy use and material extraction.

Production and heating require energy and emit pollutants; however, asphalt is highly recyclable. Modern practice emphasizes energy efficiency, lower emissions, and the use of RAP and warm-mix products.

Natural asphalt was used in ancient times; modern asphalt paving emerged with the refinement of crude oil and bitumen as a binder in the 19th and 20th centuries.