Macadam

The term refers to a special construction of macadam roads, form the road surface in three layers, each with different sizes, broken and well compacted aggregates. This design was invented by the British engineer John Loudon McAdam in the early 19th century to (often pack -layer design) to improve the durability and resilience of existing roads. Such paved roads were designated as makadamisiert.

This original design proved with the increasing motorization in particular because of the occurring dust as inadequate. Therefore, it later passed to the aggregates with tar or ( rarely) with bitumen to bind ( teergebundener macadam ). Ultimately, could not prevent the macadam construction was replaced by other constructions also this further. The reasons were particularly strong mechanization in road ( unpaved roads can only with great amount of manual installation established) and the low stability and flatness with heavy traffic loads.

In modern usage, the meaning of the term " macadam " has changed somewhat. Most so only superficially bituminous coating is commonly known (as opposed to asphalt). In addition, water- bound surfaces, such as those used in the construction of service roads on the application, attributed to the macadam construction.

Method of construction

Originally developed by McAdam in the early years of the 19th century building consisted of three layers of gravel of different grain sizes, which were applied on a curved base, with side ditches for drainage. Passed the lower two layers of gravel ( broken hand, grain size up to 8 cm ) in a total thickness of 20 cm, it then a layer of gravel was applied ( grain size up to 2.5 cm) at a thickness of 5 cm. The sheets were each separately compressed with a heavy roller, and with the addition of water. This ensured that the angular granules wedged into each other. This basic structure is sometimes referred to as water-bound macadam. This method was very labor intensive, but achieved a solid and self-draining pavement.

Development

With the advent of motor vehicles, dust was a serious problem for macadam roads. The negative pressure under fast moving vehicles sucked the dust and fine sand particles from the surface, which meant that even the coarser particles lost their connection. In addition, unpleasant dust clouds arose. We solved the problem by the addition of tar ( bitumen rare ), whereby so-called teergebundener macadam (English tarmac ) was born.

First was mixed before installing the fine rock particles with the binder and then sprinkled it on the lower unbound layers. This construction was designated Streumakadam, later also Asphaltstreumakadam. Were also the underlying coarse rock particles before installation mixed with the binder, there was talk of Mischmakadam or Asphaltmischmakadam. The invention of Tränkmakadam ( commonly referred to as Oberflächenteerung or as Asphalttränkmakadam ) was carried out in 1902 by Ernest Guglielminetti.