Asphalt is ancient, but remains a modern super-product
Children appreciate the smoothness of asphalt. To them, it can be a practical and expansive canvas that brings hopscotch and tic-tac-toe to life. To adults, it’s so ubiquitous it’s rarely noticed, unless we hit a pothole.
People are sometimes surprised to learn that asphalt is produced at petroleum refineries. Here’s a brief 101 on the process:
Crude-oil feedstock is pumped into distillation columns. The columns boil the oil to produce gas at the top, naphtha a bit further down, distillate at roughly the midpoint, and gasoil toward the base. Vacuum residue collects at the very bottom. One application of that residue is to then refine it into asphalt. Three asphalt products can be made: one for paving, one for industrial use, and one for roofing. Not all refineries produce asphalt, but many do.
Its name comes from the Greek ásphaltos, which literally means bitumen. Yes, it’s been used since the days of Ancient Greece. Here are some other asphalt applications:
Waterproofing
Asphalt is used as a membrane to coat rooftops and pipes, preventing the seepage of water that would otherwise cause damage. Historically, records show the Cree Peoples first showed the substance to Europeans in 1719 through the Hudson’s Bay Company. “At about 24 miles from the fork (of the Athabasca and Clearwater Rivers) are some bituminous fountains into which a pole of 20 feet long may be inserted without the least resistance,” marvelled one Alexander MacKenzie in 1787, who noted it smelled of sea coal. [2]
Arboriculture
A wounded tree or plant is susceptible to invasive bugs and bacteria. Liquid asphalt is the applicant of choice for sealing breakages and gashes.
Ink and paint
Black newspaper ink is 7 per cent asphalt and 75 per cent naphthenic oil, which is also produced in refineries. Coloured ink contains less of it. Similarly, paints often contain asphalt. [4]
Roofing
Asphalt is one component in asphalt roofing shingles, along with mineral fiber and cementitious fillers. A different classification, organic shingles, are made of paper and made waterproof by saturation in asphalt. Fibreglass shingles are likewise coated in asphalt, and also contain urea-formaldehyde resin and have a ceramic-granule coating.
Nuclear waste disposal
Among its other modern applications, asphalt is refined into something called Radioactive Waste Encapsulation Matrix and is used to confine Plutonium, the by-product of fission [3]. Waste is immobilized by mixing it with the matrix and placed in a metallic container such as a drum, and stored appropriately.
Roads
Canada’s modern-day 416,000 km of finished roads are produced with asphalt concrete, which is a mechanical mixture of gravel and pure asphalt.
Not all paving asphalt is the same. Depending on the application, grade I-2, I-4, or I-5 might be appropriate. Roads are usually built in three layers, with a solid base, a “permanent” middle layer, and a top layer that’s designed to be replaced as needed. Parking lots and playgrounds might use a porous asphalt, which lets water drip through rather than puddling. Stone mix asphalt is sometimes used in sensitive areas because it’s 50 per cent quieter to drive on. Hot mix asphalt saves on paving costs, compacts tightly and looks finer, making it the surface of choice for residential driveways.
The latest innovation: shreds from recycled tires are mixed in with the pavement to produce a remarkably quiet drive while keeping rubber from landfills.
Stay tuned in 2019; we’ll be sharing more facts and figures about ásphaltos. Until then, smooth driving!
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[1](https://theses.lib.sfu.ca/file/thesis/4757)
[2] https://web.archive.org/web/20151123024928/http://history.alberta.ca/oilsands/resources/docs/facts_sheets09.pdf)
[3] http://asphaltmagazine.com/seven-lesser-known-uses-for-asphalt/
[4] https://www.nrc.gov/reading-rm/doc-collections/fact-sheets/radwaste.html
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