Terminology

Tarmac

Derived from the word tarmacadam; describes the type of binding agent used to coat the stone to form the macadam. Tar was a bi-product of the old gas industry before natural gas, and was used extensively in the construction of our roads. These days tar does not exist but we all still call the 'black sticky stuff', Tarmac.

Bitmac

Derived from the word bitumen macadam; describes the type of binding agent that is now used to coat the stone. Although we should be calling the 'black sticky stuff' bitmac, no one ever does, and I don't think anyone ever will.

Coated Material

Materials coated with bitumen.

Asphalt

Coated materials in the USA and other places area known as Asphalt. Asphalt or more commonly known as Hot Rolled Asphalt in the UK is the name given to a specific type of coated material mainly used as the surface course on main roads and motorways.

Bitumen

A derivative of the distillation of crude oil, now used to coat all our macadams.

Penetration

This a measure of the hardness of the bitumen and is denoted by a number. The higher the Number the softer the bitumen. ie 100 penetration bitumen is a lot harder than 200 penetration bitumen.

Subgrade

This is the natural layer that is reached when final excavation depth is achieved.

Subase

The layer of stone that sits on to the subgrade. Type 1 subbase is a graded material 40mm to dust that conforms to specific - British Standard requirements.

Scalpings

This a quarry waste product and may contain contaminates like clay.