Tarmacadam, or asphalt, was invented in 1901 by E. Purnell Hooley to seal macadam roads. It consists of tar sprayed on macadam and pressed with a roller. Although no longer used for paving, it is still used for airport runways and some roads. Macadamized roads, invented by John Loudon McAdam, consist of three layers of aggregate materials. Tarmacadam can be repaired by resurfacing the top layer and is still used in some parts of the world.
Tarmacadam, also known as asphalt, is a portmanteau abbreviation for tar-penetrating macadam. Asphalt was used to pave roads and other large flat surfaces, and although asphalt is no longer used for paving due to the introduction of asphalt, the word asphalt is still used in reference to airport runways and some roadways in many parts of the world, especially in the former British colonies. Tarmacadam was patented by E. Purnell Hooley in 1901, who later sold the invention to Wolverhampton MP, who relaunched the product with great success in 1905. Tarmac Limited, the tarmacadam arm of Wolverhampton, remains a major player in materials heavy British construction boats.
Tarmacadam is a rearrangement of macadam, a type of road construction invented by John Loudon McAdam in the early 19th century. Macadamized roads consist of three layers of aggregate materials of decreasing size, with the bottom layer being the largest and heaviest. Each layer is pressed with a roller to flatten it and force the materials to bond together. The resulting pavement was strong and drained easily, but as motor vehicles became widespread, the macadam was unable to withstand the heavy wear and tear and began to disintegrate.
Tarmacadam began as a way to seal macadam, preventing roads from cracking under heavy use and keeping dust to a minimum. Tarmacadam is created by spraying tar along a macadam road to further bond it and pressing the surface with a roller to drive the tar deep into the macadam. Asphalt roads used to be very durable and still exist in some countries, although they are slowly being replaced by asphalt concrete, made from petroleum by-products.
Some roads on the East Coast of the United States have their original paved surfaces, and many East Coast residents still refer to the roads as “macadam,” even though they have since been resurfaced with asphalt. Many developing nations have also kept their roads and runways paved. Tarmacadam can be repaired by scarring and resurfacing the top layer of small materials, and this is still done in some parts of the world to avoid the more costly complete replacement that asphalt pavement involves.
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