macadam

thumb|An illustration of the first macadamized road in the United States between Boonsboro, Maryland|Boonsboro and Hagerstown in [[Maryland in 1823; in the foreground, workers are breaking stones "so as not to exceed in weight or to pass a ring".]] Macadam is a type of road construction pioneered by Scottish engineer John Loudon McAdam , in which crushed stone is placed in shallow, convex layers and compacted thoroughly. A binding layer of stone dust (crushed stone from the original material) may form; it may also, after rolling, be covered with a cement or bituminous binder to keep dust and stones together. The method simplified what had been considered state-of-the-art at that point.

== Predecessors == ===Pierre-Marie-Jérôme Trésaguet=== Pierre-Marie-Jérôme Trésaguet is sometimes considered the first person to bring post-Roman science to road building. A Frenchman from an engineering family, he worked paving roads in Paris from 1757 to 1764. As chief engineer of road construction of Limoges, he had opportunity to develop a better and cheaper method of road construction. In 1775, Tresaguet became engineer-general and presented his answer for road improvement in France, which soon became standard practice there.