Tarmac - Origins

Origins

Babylon, in 625 BCE was the first city to have its streets paved with tar. More than 2,000 years later, John Loudon McAdam invented a road construction method called macadamisation. These roads were adequate for use by horses and carriages or coaches, but they were very dusty and subject to erosion with heavy rain. Later on, they did not hold up to higher speed motor vehicle use. Methods to stabilise macadam roads with tar date back to at least 1834, when John Henry Cassell, operating from Cassell's Patent Lava Stone Works in Millwall, patented "Pitch Macadam". This method involved spreading tar on the subgrade, then placing a typical macadam layer and then sealing the macadam with a mixture of tar and sand. Tar-grouted macadam was also in use well before 1900, and involved scarifying the surface of an existing macadam pavement, spreading tar and re-compacting. Although the use of tar in road construction was known in the 19th century, it was little used and was not introduced on a large scale until the motor car arrived on the scene in the early 20th century.

Hooley's 1901 patent for Tarmac involved mechanically mixing tar and aggregate prior to lay-down, and then compacting the mixture with a steam roller. The tar was modified by adding small amounts of Portland cement, resin and pitch.