Tarmac, also referred to as Tarmacadam or Concrete Asphalt.
A mixture of bitumen and aggregate laid and compacted for Roads, Paved areas.
Zillions of tones of this material have been laid since its conception. Babylon was the first City known to have been paved using tarmac material way back in 625BC.
The first recorded tarmac patent was recorded in 1901 by Edgar Purnell Hooley in 1901
A Scot – John Loudon McAdam invented the process by which it was used for road construction called Macadamisation.
Most homeowners will only be interested in Tarmac for Driveways and access roads.
As with all paving the finished product is only as good as the base it is laid on.
The first thing is to think about is. - Its intended use.
Is it Pedestrian traffic only or for vehicles to park or drive on.
Remember at some point you will need a delivery involving a lorry, maybe a skip or delivery of an appliance / furniture.
For this type of use you will require a well-compacted sub base at a minimum of 150mm thick preferably constructed using a designed sub base material like MOT type 1. This must be laid before it is overlaid with tarmac.
You will also need to work out where the surface rainwater will flow. (Tarmac is water impermeable) – these are called falls. Most small drives can be constructed so the water falls to the front and disperses into the road. If the area is large Local authorities may require you to find an alternate solution. This could be by excavating a soak away for the water to disperse.
It also maybe also possible to link into your existing surface water drain system.
Tarmac is generally laid using a base course and a wearing course.
The base course. Material is constructed using bitumen & will have aggregate of 20mm. This material is either laid by hand or machine at a thickness not less than 50mm. The material is then well compacted using a mechanical roller.
The wearing course. Material is same as above but uses a finer aggregate typically 6mm. This provides a tighter closed surface finish. As with the base course it is compacted with a roller.
Overlaying. It is also possible to use a tarmac wearing course as an overlay to existing worn tarmac or concrete. However the existing surface needs to be prepared and over coated with a tack coat primer first.
Colours. Wearing course is available in Black, Red and green. Pigments are added in the manufacturing stage .– Colours are more expensive.
Its also possible to have a fine gravel finish bonded to the tarmac either using a hot or cold bonding solution- in this case the wearing course is omitted and the stone chips are bonded directly to the base course.
Tarmac at its edges needs to be retained by some form of kerb or edging. If its just a pathway timber will suffice. For drives or parking areas something more substantial is required like concrete or brick edging.