Tarmac
Overview
 
Tarmac is a type of road surface. Tarmac refers to a material patented by Edgar Purnell Hooley in 1901. The term is also used, with varying degrees of correctness, for a variety of other materials, including tar-grout
Grout
Grout is a construction material used to embed rebars in masonry walls, connect sections of pre-cast concrete, fill voids, and seal joints . Grout is generally composed of a mixture of water, cement, sand, often color tint, and sometimes fine gravel...

ed macadam
Macadam
Macadam is a type of road construction pioneered by the Scotsman John Loudon McAdam in around 1820. The method simplified what had been considered state-of-the-art at that point...

, Tarvia, bituminous surface treatments and even modern asphalt concrete
Asphalt concrete
Asphalt concrete is a composite material commonly used in construction projects such as road surfaces, airports and parking lots. It consists of asphalt and mineral aggregate mixed together, then laid down in layers and compacted...

.
The first known city to have its streets paved with tar was in the 8th century AD. More than 1,000 years later, John Loudon McAdam
John Loudon McAdam
John Loudon McAdam was a Scottish engineer and road-builder. He invented a new process, "macadamisation", for building roads with a smooth hard surface that would be more durable and less muddy than soil-based tracks....

 invented a road construction method called macadam
Macadam
Macadam is a type of road construction pioneered by the Scotsman John Loudon McAdam in around 1820. The method simplified what had been considered state-of-the-art at that point...

isation.
Encyclopedia
Tarmac is a type of road surface. Tarmac refers to a material patented by Edgar Purnell Hooley in 1901. The term is also used, with varying degrees of correctness, for a variety of other materials, including tar-grout
Grout
Grout is a construction material used to embed rebars in masonry walls, connect sections of pre-cast concrete, fill voids, and seal joints . Grout is generally composed of a mixture of water, cement, sand, often color tint, and sometimes fine gravel...

ed macadam
Macadam
Macadam is a type of road construction pioneered by the Scotsman John Loudon McAdam in around 1820. The method simplified what had been considered state-of-the-art at that point...

, Tarvia, bituminous surface treatments and even modern asphalt concrete
Asphalt concrete
Asphalt concrete is a composite material commonly used in construction projects such as road surfaces, airports and parking lots. It consists of asphalt and mineral aggregate mixed together, then laid down in layers and compacted...

.

Origins

The first known city to have its streets paved with tar was in the 8th century AD. More than 1,000 years later, John Loudon McAdam
John Loudon McAdam
John Loudon McAdam was a Scottish engineer and road-builder. He invented a new process, "macadamisation", for building roads with a smooth hard surface that would be more durable and less muddy than soil-based tracks....

 invented a road construction method called macadam
Macadam
Macadam is a type of road construction pioneered by the Scotsman John Loudon McAdam in around 1820. The method simplified what had been considered state-of-the-art at that point...

isation. These roads were adequate for use by horses and carriages or coaches, but they were very dusty and subject to erosion with heavy rain. Later on, they did not hold up to higher speed motor vehicle use. Methods to stabilise macadam roads with tar date back to at least 1834, when John Henry Cassell, operating from Cassell's Patent Lava Stone Works in Millwall
Millwall
Millwall is an area in London, on the western side of the Isle of Dogs, in the London Borough of Tower Hamlets. It lies to the south of the developments at West India Docks, including Canary Wharf.-History:...

, patented "Pitch Macadam". This method involved spreading tar on the subgrade
Subgrade
In transport engineering, subgrade is the native material underneath a constructed road, pavement or railway track. It is also called formation level.The term can also refer to imported material that has been used to build an embankment....

, 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. 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 motor car arrived on the scene in the early 20th century.

Hooley's 1901 patent for Tarmac involved mechanically mixing tar and aggregate prior to lay-down, and then compacting the mixture with a steam roller
Steamroller
A steamroller is a form of road roller – a type of heavy construction machinery used for levelling surfaces, such as roads or airfields – that is powered by a steam engine...

. The tar was modified by adding small amounts of Portland cement
Portland cement
Portland cement is the most common type of cement in general use around the world because it is a basic ingredient of concrete, mortar, stucco and most non-specialty grout...

, resin
Resin
Resin in the most specific use of the term is a hydrocarbon secretion of many plants, particularly coniferous trees. Resins are valued for their chemical properties and associated uses, such as the production of varnishes, adhesives, and food glazing agents; as an important source of raw materials...

 and pitch
Pitch (resin)
Pitch is the name for any of a number of viscoelastic, solid polymers. Pitch can be made from petroleum products or plants. Petroleum-derived pitch is also called bitumen. Pitch produced from plants is also known as resin. Products made from plant resin are also known as rosin.Pitch was...

.

Later developments

As petroleum
Petroleum
Petroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...

 production increased, the by-product asphalt
Asphalt
Asphalt or , also known as bitumen, is a sticky, black and highly viscous liquid or semi-solid that is present in most crude petroleums and in some natural deposits, it is a substance classed as a pitch...

 became available in greater 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 airport
Airport
An airport is a location where aircraft such as fixed-wing aircraft, helicopters, and blimps take off and land. Aircraft may be stored or maintained at an airport...

s, especially the airport ramp
Airport ramp
The airport ramp or apron is part of an airport. It is usually the area where aircraft are parked, unloaded or loaded, refueled or boarded. Although the use of the apron is covered by regulations, such as lighting on vehicles, it is typically more accessible to users than the runway or taxiway...

 or "apron", near the terminals
Airport terminal
An airport terminal is a building at an airport where passengers transfer between ground transportation and the facilities that allow them to board and disembark from aircraft....

 despite the fact that many of these areas are in fact often made of concrete
Concrete
Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...

. The Wick Airport
Wick Airport
Wick Airport is located north of the town of Wick in Caithness at the north-eastern extremity of the mainland of Scotland. It is owned and maintained by Highlands and Islands Airports Limited....

 at Wick in Caithness
Caithness
Caithness is a registration county, lieutenancy area and historic local government area of Scotland. The name was used also for the earldom of Caithness and the Caithness constituency of the Parliament of the United Kingdom . Boundaries are not identical in all contexts, but the Caithness area is...

, Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...

 is one of the few airports that still has a real tarmac runway.

Tarmac is a registered trademark, although it is frequently used with a lower-case initial letter.

See also

  • History of road transport
    History of road transport
    The history of road transport started with the development of tracks by humans and their beasts of burden.- Early roads :The first forms of road transport were horses, oxen or even humans carrying goods over tracks that often followed game trails, such as the Natchez Trace. In the Stone Age humans...

     – covers the development of road-building techniques
  • Asphalt concrete
    Asphalt concrete
    Asphalt concrete is a composite material commonly used in construction projects such as road surfaces, airports and parking lots. It consists of asphalt and mineral aggregate mixed together, then laid down in layers and compacted...

  • Pavement (material)
    Pavement (material)
    Road surface or pavement is the durable surface material laid down on an area intended to sustain vehicular or foot traffic, such as a road or walkway. In the past cobblestones and granite setts were extensively used, but these surfaces have mostly been replaced by asphalt or concrete. Such...

  • Tarmac (company)
    Tarmac (company)
    Tarmac is a company that is based in Wolverhampton in the United Kingdom and operates internationally. The company produces aggregates and road-surfacing materials, including tarmacadam, from which the company's name is derived...

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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