Telling Tarmac, Bitumen, and Asphalt Apart
BituChem talks about tarmac, bitumen and asphalt a lot on our website — road surfacing and highway repair is what we do, after all. But if you don’t spend a lot of time in the road maintenance industry or have a background in organic chemistry or engineering, it can be difficult to know the difference between the three highway surfaces.
In this article, we’re going to outline the differences between the three (if any) highway bituminous products and a little history about them.
What is Tarmac?
Going chronologically, the first of our three terms is Tarmac. This road substance was traditionally applied hot and then allowed to dry as it cooled.
Tarmac, short for Tarmacadam, is the material created when a layer of crushed aggregate or stone is mixed with molten tar. This new mixture is laid and then compacted with a vibrating roller to form a smooth surface. Tarmac was invented by Edward Purnell Hooley in 1901. However, Purnell’s work was based on experiments done by Scottish engineer John Loud McAdam — hence the name.
During the early part of the 20th century, Tarmac was the preferred material to use as a road surface. It created a smooth surface when solid — which was extremely useful during the increased industrialization of the period. Another reason why Tarmac was the prefered material for road surfacing was that it didn’t create any dust and was much stronger than stone or concrete.
However, while Tarmac was an improvement on the earlier methods of road surfacing, it had its own weaknesses. Tarmac required an incredible amount of physical labour to lay properly, as well as an industrial oven to keep the tar molten.
Tarmac also decayed relatively quickly, meaning that roads could look shoddy within ten years. Finally, Tarmac, with its hard, industrial, uniformly grey appearance, was inappropriate material for decorative paving and park footpaths. Because of these drawbacks, new material was needed.
What is Asphalt?
That material was Asphalt. Or, to use its proper name, Asphalt Concrete.
On this site, we sometimes use the terms Asphalt and Bitumen interchangeably. This is intentional, as Bitumen is a key component of Asphalt — as a result, there is some natural conflation between the two terms.
Like Tarmac, Asphalt is a mix of aggregate material and other materials. In the case of Tarmac, this is tar. For Asphalt, however, we use Bitumen. Elementally, that is the key difference between the two.
Although Bitumen had been used in construction before the early 20th century, the difficulty in sourcing enough of the material made its mass adoption highly unlikely.
By the mid-20th century, however, distillation techniques and infrastructure processes had improved to such an extent it was possible to source bitumen from natural sources and create it artificially in high enough amounts that mass adoption was possible for the first time.
This, combined with a greater emphasis on more striking colours in terms of construction materials and greater emphasis on aesthetics in post-industrial architectural styles, meant that Asphalt quickly overcame Tarmac in popularity.
Since that time, the uses of Asphalt have increased dramatically. While many roads and paths are still entirely laid using Bitumen-based Asphalt Concrete, today there’s a greater emphasis on sustainability. As a result, more Bitumen and Asphalt is recycled than ever before.
Asphalt continues to be used for highway repairs and pavement waterproofing.
Looking To The Future
At BituChem, we’re never content to sit on our laurels and wait. We’re always looking to the future for ways of making our customers’ projects stronger and more aesthetically pleasing.
For more information on how BituChem can make a difference with your decorative paving, school surfacing, pothole repair, or park footpaths, give us a call today.