Tarmac is a bituminous material used in paving, also known as Tarmac™ or Asphalt. Tarmac is comprised of tar and broken stone which is mixed and shaped during the paving process, usually laid out and brushed evenly and then compressed by machinery such as a modern vibrating roller.
Tarmac is suitable for areas to be used by vehicles, such as roads, car parks, drives and forecourts. Tarmac can also be used for paths, although it is not advisable using Tarmac for garden paths. In general, all Tarmac installations should be machine or hand laid .
The sub-base and base courses may be constructed from more than one individual layer of the specified material, but for our purposes, we will consider each layer as being a single entity.
Sometimes, levels permitting, an existing bitmac or concrete surface can be overlaid with a new surface course. This is acceptable provided that the new surfacing is properly bonded to the old surface. It is not good practice to overlay existing flags/slabs.
Sub-base This is essential if the pavement is to last longer than a couple of years. Do not employ any contractor who tells you that a sub-base is not required, unless there is a suitable existing sub-base or base layer.
Binder course This is a load-bearing, strengthening layer of the pavement and should be at least 40mm, preferably 50mm thick. The material used as a binder course is 'chunkier' than a wearing course, usually comprising 20mm or 28mm aggregate in a bitumen binder, known as Dense Bitumen Macadam (DBM). On public highways and other heavier-use projects, the binder course may be underlain by a base layer. For binder course 50-80mm thick, use 20mm material (DBM)
For binder course 70-150mm thick, use 28mm material (DBM
