Editing Tarmacadam

{{Short description|Road surface of macadam, tar and sand}}
{{about|the road surfacing|other uses|Tarmac (disambiguation)}}

'''Tarmacadam''' or '''tarmac''' is a [[concrete]] [[road surface|road surfacing]] material made by combining [[tar]] and [[macadam]] ([[crushed stone]] and [[sand]]), patented by Welsh inventor [[Edgar Purnell Hooley]] in 1902. It is a more durable and dust-free enhancement of simple compacted stone macadam surfaces invented by Scottish engineer [[John Loudon McAdam]] in the early 19th century. The terms "tarmacadam" and "tarmac" are also used for a variety of other materials, including tar-[[grout]]ed macadam, bituminous surface treatments and modern [[asphalt concrete]].

==Origins==
[[Macadam]] roads pioneered by Scottish engineer [[John Loudon McAdam]] in the 1820s<ref>{{Cite web |title=Coloured Tarmacadam |url=https://www.colouredtarmacadam.co.uk/ |access-date=2020-11-25 |website=www.colouredtarmacadam.co.uk}}</ref> are prone to rutting and generating dust. Methods to stabilise macadam surfaces with [[tar]] date back to at least 1834 when John Henry Cassell, operating from ''Cassell's Patent Lava Stone Works'' in [[Millwall]], [[England]], patented "lava stone."<ref>[http://www.british-history.ac.uk/report.aspx?compid=46514 From: 'Northern Millwall: Tooke Town', Survey of London: volumes 43 and 44: Poplar, Blackwall and Isle of Dogs (1994), pp. 423–433] Date accessed: 24 May 2009</ref> This method involved spreading tar on the [[subgrade]], placing a typical macadam layer, and finally sealing the macadam with a mixture of tar and sand. Tar-grouted macadam was in use well before 1900 and involved scarifying the surface of an existing macadam pavement, spreading tar and re-compacting. Although the use of tar in road construction was known in the 19th century, it was little used and was not introduced on a large scale until the motorcar arrived on the scene in the early 20th century. Ironically, although [[John Loudon McAdam]] himself had been a supplier of coke for [[Archibald Cochrane, 9th Earl of Dundonald#Life|Britain's first Coal-Tar factory]], he never in his own lifetime advocated for the use of tar as a binding agent for his road designs, preferring free-draining materials (see the page [[Macadam]]).

In 1901, [[Edgar Purnell Hooley]] was walking in [[Denby]], [[Derbyshire]], when he noticed a smooth stretch of road close to an ironworks. He was informed that a barrel of tar had fallen onto the road and someone poured waste [[slag]] from the nearby furnaces to cover up the mess.<ref name="Discovery">{{cite news|title=The man who invented Tarmac|url=http://www.bbc.co.uk/nottingham/content/articles/2009/07/03/edgar_hooley_tarmac_feature.shtml|publisher=BBC|date=24 December 2016}}</ref> Hooley noticed this unintentional resurfacing had solidified the road, and there was no rutting and no dust.<ref name="Discovery"/> Hooley's 1902 [[patent]] for tarmac involved mechanically mixing tar and [[Construction aggregate|aggregate]] before lay-down and then compacting the mixture with a [[steamroller]]. The tar was modified by adding small amounts of [[Portland cement]], [[resin]] and [[pitch (resin)|pitch]].<ref>Hooley, E. Purnell, {{US patent|765975}}, "Apparatus for the preparation of tar macadam", July 26, 1904</ref> [[Nottingham]]'s Radcliffe Road became the first tarmac road in the world.<ref name="Discovery"/> In 1903 Hooley formed [[Tarmac Group|Tar Macadam Syndicate Ltd]] and registered tarmac as a trademark.<ref name="Discovery" />

==Later developments==
As [[petroleum]] production increased, the by-product [[bitumen]] became available in greater quantities and largely supplanted coal tar. The macadam construction process quickly became obsolete because of the onerous and impractical manual labour required. The somewhat similar tar and chip method, also known as bituminous surface treatment (BST) or [[chipseal]], 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 [[airport]]s,<ref name=OED2011>{{cite encyclopedia |title=Tarmac, n |date=June 2011 |publisher=Oxford University Press |encyclopedia=[[Oxford English Dictionary]]}}</ref> especially the [[airport apron|apron]] near [[airport terminal]]s,<ref>{{cite web |url= https://www.genericides.org/trademark/tarmac|title= Has tarmac become a generic trademark?  |access-date= February 17, 2021 |website= genericides.org }}</ref> although these areas are often made of [[concrete]]. Similarly in the UK, the word ''tarmac'' is much more commonly used by the public when referring to [[asphalt concrete]].

==See also==
* [[History of road transport]]

==References==
{{Reflist}}

== External links ==
* {{Wiktionary-inline}}

{{Road types}}

[[Category:Asphalt]]
[[Category:Brands that became generic]]
[[Category:English inventions]]
[[Category:Pavements]]