What is bitumen and how is it made
October 28, 2019
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November 12, 2018
Post by: Marie Greewood
September 07, 2015
Ahhh, the smells of summer….fish and chips on the beach, freshly mown grass, sun-lotion (particularly those coconut ones) and…erm, the smell of hot bitumen being laid on the road network. And the sights of summer? Well depending on the kind of holiday you’ve just had, they may be golden sands and turquoise waters. Or perhaps its massive traffic jams that come to mind, as road crews up and down the country mend, fill and construct new highways. But why oh why can’t they do it when the roads are quiet, instead of the very time that everyone goes on holiday…?
First things first, what is bitumen (sometimes referred to as asphalt)?Well, it is a specialist fuel grade, typically only produced in about 65% of refineries around the world and with a yield of only 3-4% of the total crude slate (see the below image on the oil refining process). Bituminous crudes from the likes of Venezuela and Trinidad tend to produce much more, but these require a more specialised refining process, way beyond the capacity of most standard refineries. The product itself is foul, black and very sticky – so full of carbon that it cannot be used for combustion (unlike gasoline, diesel and jet fuel). In fact it has so much carbon that unless it is kept heated to a temperature of about 150 deg C, it solidifies into a rock-hard wax. Therefore most bitumen is loaded into road tankers near to boiling point (for maximum viscosity) and this makes the job of a bitumen tanker driver extremely hazardous - think full protective head and body-suits for all parts of the body.
Yet despite this heavy carbon content, bitumen can justifiably claim to be one of the most environmentally friendly crude oil products. What!? How can such a filthy product be environmentally friendly? Well the answer is that this product is not burned and therefore does not produce any CO2 emissions; it may well be packed full of horrible stuff, but bitumen is only used as a construction material and not for its energy generating, combustion qualities. Furthermore, bitumen can and is re-cycled – in some countries recycling rates for bitumen are as high as 70%. Simply reheat the product, allow it to melt and hey presto its ready to be used again…
And what are those uses?
Well if ever there was a crude oil product that the modern world could not exist without, it is bitumen. When mixed with sand, gravel and crushed rock before being laid pancake flat, bitumen becomes a road. Not only does the sticky nature of the product quite literally glue all the construction material together, its water-proofing characteristics are unparalleled, which means that rain water does not permeate into the road construction and simply runs off. When not being used for roads, bitumen also comes in pretty handy for the construction of pavements. And cycle-tracks. And playgrounds. Oh yes, and runways, jetties, bus-stops, railway platforms and car-parks. Do I need to go on? A phenomenal 90% of the total world road network contains bitumen. In Europe alone, that means 4m miles of road that are reliant on bitumen.
In fact this wonder product has no end of modern uses. Almost all modern houses are weather-proofed using bitumen, so that before roof tiles go on a bitumen lining is laid to make sure everything keeps dry inside. And the work continues inside the house too. Ever wondered why damp from the floorboards doesn’t permeate up through your front-room carpet? Well that’s because of the bitumen coating that lies underneath. And then there’s the water-proof paint. And the pipe sealants. And the gutter-proofing….I think we can safely say that no country should be more grateful to bitumen than damp old Britain. Bitumen really is Britain’s best friend!
Why the summer activity binge though (50% of bitumen in Europe is consumed between June and September)?
Well, working with bitumen requires warm and dry weather as laying bitumen in the rain has about as much effect as applying paint to a wet surface. So if new roads and road extensions have to be built, then they have to be built in the summer. It may not have seemed like it on your last holiday (particularly if you stayed in the UK), but the driest months of the year are indeed June, July and August. That’s 3 short months to get things done, not forgetting the fact that when it comes to highways, the serious pounding of the tarmac comes in the winter – particularly in the colder climates of the Northern Hemisphere where water freezes, expands and ends up cracking surfaces. Come the summer then, all of these holes, cracks and craters also have to be repaired in the same short period of time. So next time you see the boys from the black stuff holding up the traffic, don’t curse them. They probably don’t want to be working during the holidays themselves. Instead we should thank them for quite literally holding our infrastructure together. But don’t get out the car to tell them that – that will just cause an even bigger traffic jam. A thumbs-up will suffice!