Tarmacadam is a road surface made from crushed stone and bitumen. The spelling of this word is unique, as it combines the shortened form of "tar" with "macadam," the surname of John Loudon McAdam, who developed the technique of road construction using layers of crushed stone. The correct pronunciation is /tɑːməkædəm/ with the stress on the second syllable. This spelling has its origins in Scotland, where McAdam conducted his experiments in road building.
Tarmacadam is a noun that refers to a type of road surfacing material. It is typically a black, smooth, and solid substance that is created by mixing crushed stone or aggregate with hot bitumen or tar. The name "tarmacadam" is derived from the combination of "tar" and "macadam," as it combines the use of tar with the macadam construction method, which involves layering and compacting crushed stones.
Tarmacadam is widely used for paving roads, driveways, parking lots, and other surfaces that require durability, resistance to traffic loads, and a smooth finish. It provides a hard and level surface that is capable of withstanding heavy vehicular traffic while offering good skid resistance.
The process of laying tarmacadam involves several steps. First, the sub-base of the surface is prepared, followed by placing a layer of crushed stone or aggregate, often known as the base course. The hot mixture of bitumen or tar is then poured over the base course, allowing it to fill the gaps between the stones. This is followed by the final layer, often referred to as the wearing course, which is a finer grade of aggregate that is also bound by the tar or bitumen.
Tarmacadam offers numerous benefits, such as reduced dust and mud, improved drainage, ease of maintenance, and the ability to withstand extreme weather conditions. It has been widely used in road construction since the mid-19th century and continues to be a popular choice for surfacing applications due to its durability and long lifespan.
The word "tarmacadam" is derived from two components: "tar" and "macadam".
"Tar" refers to a black, sticky substance derived from the distillation of coal or wood, commonly used as a binder or adhesive in road construction. It has been used since ancient times for various purposes, including waterproofing and preserving wood.
"Macadam" honors the Scottish engineer John Loudon McAdam (1756-1836), who is considered the father of modern road construction. He revolutionized road building techniques by introducing the concept of macadamization, which involved creating a solid road surface by layering small stones of graded sizes and compacting them.
The term "tarmacadam" was coined to describe a road construction method that combined these two elements. It referred to roads built by applying a layer of tar as a binding agent over a foundation of compacted stone layers.