Macadam is a type of road construction pioneered by the Scotsman John Loudon McAdam in around 1820. A road is an identifiable route, way or path between two or more places. Scotland ( Gaelic: Alba) is a Country in northwest Europethat occupies the northern third of the island of Great Britain. John Loudon McAdam ( September 21 1756 – November 26 1836) was a Scottish Engineer and Road -builder Year 1820 ( MDCCCXX) was a Leap year starting on Saturday (link will display the full calendar of the Gregorian calendar (or a Leap year It consisted of creating three layers of stones laid on a crowned subgrade with side ditches for drainage. In Highway engineering, subgrade is the native material underneath a constructed pavement The first two layers consisted of angular hand-broken aggregate, maximum size 3 inches (75 mm), to a total depth of about 8 inches (200 mm). Aggregate is the component of a Composite material used to resist compressive stress Inches redirects here To see the Les Savy Fav album see Inches. The Millimetre ( American spelling: millimeter, symbol mm) is a unit of Length in the Metric system, equal to The third layer was about 2 inches (50 mm) thick with a maximum aggregate size of 1 inch (25 mm). Each layer would be compacted with a heavy roller, causing the angular stones to lock together. A road roller (sometimes called a roller-compactor, or just roller) is a Compactor type Engineering vehicle used to compact soil

Water-bound macadam

This basic method of construction is sometimes known as "water-bound macadam". Although this method required a great deal of manual labor, it resulted in a strong and free-draining pavement. Roads constructed in this manner were described as "macadamized".

Tar-bound macadam

With the advent of motor vehicles, dust became a serious problem on macadam roads. A motor Vehicle is a Machine which incorporates a motor (sometimes known as an Engine) and which is used for Transportation The vacuum created under fast-moving vehicles sucks dust from the road surface, creating unpleasant dust clouds and a gradual raveling (pulling apart) of the road material. This vacuum means "absence of matter" or "an empty area or space" for the cleaning appliance see Vacuum cleaner. This problem was later rectified by spraying tar on the surface to create "tar-bound macadam" (tarmac). Tar is a viscous black Liquid derived from the Destructive distillation of organic matter Tarmac (short for tarmacadam, a Portmanteau for Tar -penetration Macadam) is a type of highway surface, pioneered by John While macadam roads have now been resurfaced in most developed countries, some are preserved along stretches of roads such as the United States' National Road. The term developed country, or advanced country, is used to categorize countries with developed Economies in which the tertiary and quaternary sectors The United States of America —commonly referred to as the US 40svg|right|100px|thumb|The National Road is now included as part of U Due to uses of macadam as a road surface in former times, roads in some parts of the United States (as parts of Pennsylvania) are often referred to as macadam, even though they might be made of asphalt or concrete. Asphalt ( is a sticky black and highly viscous liquid or semi-solid that is present in most crude Petroleums and in some natural deposits sometimes termed asphaltum Concrete is a construction material composed of Cement (commonly Portland cement) as well as other cementitious materials such as Fly ash and Slag