What is asphalt?

You have traveled on a wonder today, whether you drove, rode a bus, walked or flew.

Our transportation-dependent advanced society wouldn’t be possible without asphalt.

What’s the most recycled material in the US? Not glass, plastic, or paper. Whether you go by gross tonnage or percentage, recycled asphalt tops the list every time.

What is asphalt?

Let’s call the black, gooey form of petroleum that seeps out of the ground asphalt/bitumen, since it has different names in the US and Britain, depending on use.

Petroleum forms over geologic time when the bodies of algae and other organisms are deposited in sediments after death. These deposits get buried under more and more sediments and eventually the entire formation turns into rock.

This rocky burden applies pressure to the petroleum. Because it gets hotter the further you go down, the petroleum also “cooks.”
The end result of all this pressure and heat is a very viscous, black substance that can seep upwards and eventually reach the surface.

Misconceptions about asphalt

The “tar” in La Brea Tar Pits isn’t really tar, which comes from coal. It’s asphalt/bitumen. No volcanism is involved.

The “pitch” in Trinidad’s Pitch Lake is really asphalt/bitumen, too.

It’s not related to pine pitch, of course.

It’s not petroleum pitch, either. That’s a residual of petroleum cracking and has very different chemical composition and properties.

What is asphalt used for?

Some 40,000 years ago, the Neanderthals used asphalt/bitumen as an adhesive when making their stone tools, just as did early Native Americans.

The word “mummy” comes from the Arabic and/or Persian word for asphalt/bitumen. The Egyptians got this embalming material from the Dead Sea, which the Romans called Palus Asphaltites (Asphalt Lake).

Asphalt/bitumen has always been a good waterproofing material. This made it very valuable when shipping first developed. Human nature being what it, the first known battle over a hydrocarbon resource, according to Wikipedia, happened in 312 BC when the Seleucids and the Nabateans fought over asphalt/bitumen.

*That battle may or may not have happened here, but the Nabataeans definitely built this place. No word on whether Junior helped out.*

Then we started to play with asphalt/bitumen, first in the Far East, where it was boiled to make a material that could be shaped while hot. This then cooled into a very hard material that was used for waterproofing as well as art.

Today, we use complex distillation processes to produce asphalt/bitumen. Most of the 108,199 thousand metric tons the world used in 2010 was man-made.

Where does it all go?

Waterproofing has always been one of its main uses (today you’ll find it in roof shingles), but asphalt paving has been around in Europe since the 1830s and in the US since around 1870.

Since the early 21st century, upgrading natural asphalt/bitumen into crude oil has become profitable, Canada – which has most of the world’s known natural asphalt/bitumen in its oil sands – has been producing well over a million barrels of crude asphalt/bitumen a day.

Other uses for this handy material have included, oddly enough, photography, as well as in oil paintings (it didn’t work out very well, as asphalt/bitumen destroyed the finish and other colors).