Tarmac
From Wikipedia, the free encyclopedia
Tarmac (short for tarmacadam, a portmanteau for tar-penetration macadam) is a type of highway surface. Strictly speaking, Tarmac refers to a material patented by E. Purnell Hooley in 1901. The term is also used, with varying degrees of correctness, for a variety of other materials, including tar-grouted macadam, Tarvia, bituminous surface treatments and even modern asphalt concrete.
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[edit] Origins
Macadamized roads were adequate for use by horses and carriages or coaches, but they were very dusty, subject to erosion with heavy rain and did not hold up to higher speed motor vehicle use. Methods to stabilize macadam roads with tar date back to at least 1834, when Henry Cassell patented "Pitch Macadam". This method involved spreading tar on the subgrade, then placing a typical macadam layer and then sealing the macadam with a mixture of tar and sand. Tar-grouted macadam was also in use well before 1900, and involved scarifying the surface of an existing macadam pavement, spreading tar and re-compacting. Hooley's patent for Tarmac involved mechanically mixing tar and aggregate prior to lay-down, and then compacting the mixture with a steam roller. The tar was modified with the addition of small amounts of Portland cement, resin and pitch.
[edit] Commercial activities
This observation inspired Hooley to develop and patent Tarmac in the United Kingdom, and, later, in the United States. He called his company Tar Macadam (Purnell Hooley's Patent) Syndicate Limited, but unfortunately he had trouble selling his product as he was not a very competent businessman. His company was soon bought out by the Wolverhampton Member of Parliament, Sir Alfred Hickman, the owner of a steelworks that produced large quantities of waste slag. The Tarmac company was relaunched in 1905 and became an immediate success: it remains a major player in the UK market for heavy building materials.
[edit] Later developments
As petroleum production increased, the byproduct asphalt became available in huge quantities and largely supplanted tar due to its reduced temperature sensitivity. The Macadam construction process also became quickly obsolete due to its high manual labour requirement; however, the somewhat similar tar and chip method, also known as bituminous surface treatment (BST), remains popular.
While the specific Tarmac pavement is not common in some countries today, many people use the word to refer to generic paved areas at airports, especially the airport ramp or "apron", near the terminals despite the fact that many of these areas are in fact made of concrete. This term seems to have been popularized when it become part of the news lexicon following live coverage of the Entebbe hijacking in 1976, where "Tarmac" was frequently used by the on-scene BBC reporter in describing the hijack scene. The term 'hardstanding' is also used for concrete aprons. The Wick Airport at Wick in Caithness, Scotland is one of the few airports that still has a real Tarmac runway.
[edit] Patents
- Hooley, E. Purnell, U.S. Patent 765975 , "Apparatus for the preparation of tar macadam", July 26, 1904.
[edit] See also
| Types of road | |
|---|---|
| High-speed access via interchanges |
Autobahn • Autopista • Autoroute • Autostrada • Auto-estrada • Freeway • Lebuhraya • Motorway |
| High-speed other types of access |
2+1 road • Divided highway • Expressway • Farm to Market Road • Highway • Parkway • Super two |
| Low speed | Arterial road • Boulevard • Frontage road • Road • Street |
| Low speed low traffic | Alley • Cul-de-sac • Driveway • Lane |
| Other | Dual carriageway • Interchange • Range road • Roundabout • Toll road |
| Surface types | Asphalt concrete • Brick • Cobblestone • Concrete • Corduroy road • Dirt road • Gravel road • Ice road • Macadam • Oiled road • Plank road • Tarmac • Winter road |
