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[[File:University of Queensland Pitch drop experiment-white bg.jpg|thumb|upright|The University of Queensland [[pitch drop experiment]], demonstrating the [[viscosity]] of bitumen]]
'''Bitumen''' ({{IPAc-en|uk|ˈ|b|ɪ|tʃ|ʊ|m|ɪ|n}} {{respell|
About 70% of annual bitumen production is destined for [[
In [[
Naturally occurring bitumen is sometimes specified by the term
==Terminology==
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The components of bitumen include four main classes of compounds:
* Naphthene aromatics ([[naphthalene]]), consisting of partially hydrogenated polycyclic aromatic compounds
* Polar aromatics, consisting of high [[molecular weight]] [[phenols]] and [[carboxylic acid]]s produced by [[partial oxidation]] of the material
* [[Saturated hydrocarbons]]; the percentage of saturated compounds in asphalt correlates with its softening point
* Asphaltenes, consisting of high molecular weight phenols and [[heterocyclic compound]]s
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===Additives, mixtures and contaminants===
For economic and other reasons, bitumen is sometimes sold combined with other materials, often without being labeled as anything other than simply "bitumen".<ref name="whats_in_your_asphalt_2017_09_fhwa">Arnold, Terence S. (senior research chemist, Pavement Materials Team, Office of Infrastructure Research and Development, [[Federal Highway Administration]]; Federal lab manager for the chemistry lab, [[Turner-Fairbank Highway Research Center]]; fellow of the [[Royal Society of Chemistry]] in the United Kingdom), [https://
Of particular note is the use of [[Automotive oil recycling#REOB|re-refined engine oil bottoms – "REOB" or "REOBs"]]{{snd}}the residue of [[Automotive oil recycling|recycled automotive engine oil]] collected from the bottoms of re-refining [[vacuum distillation]] towers, in the manufacture of asphalt. REOB contains various elements and compounds found in recycled engine oil: additives to the original oil and materials accumulating from its circulation in the engine (typically iron and copper). Some research has indicated a correlation between this adulteration of bitumen and poorer-performing pavement.<ref name="whats_in_your_asphalt_2017_09_fhwa" />
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The Canadian province of [[Alberta]] has most of the world's reserves, in three huge deposits covering {{convert|142000|km2}}, an area larger than [[England]] or [[New York state]]. These bituminous sands contain {{convert|166|Goilbbl}} of commercially established oil reserves, giving Canada the third largest [[oil reserves]] in the world. Although historically it was used without refining to pave roads, nearly all of the output is now used as [[raw material]] for [[Oil refinery|oil refineries]] in Canada and the United States.<ref name="ST98"/>
The world's largest deposit of natural bitumen, known as the [[Athabasca oil sands]], is located in the [[McMurray Formation]] of Northern Alberta. This formation is from the early [[Cretaceous]], and is composed of numerous [[lens (geology)|lenses]] of oil-bearing sand with up to 20% oil.<ref name=bunger>{{cite journal | last1 = Bunger | first1 = J. | last2 = Thomas | first2 = K. | last3 = Dorrence | first3 = S. | year = 1979 | title = Compound types and properties of Utah and Athabasca tar sand bitumens | journal = Fuel | volume = 58 | issue = 3| pages = 183–195 | doi=10.1016/0016-2361(79)90116-9| bibcode = 1979Fuel...58..183B }}</ref> Isotopic studies show the oil deposits to be about 110 million years old.<ref>{{cite journal | last1 = Selby | first1 = D. | last2 = Creaser | first2 = R. | year = 2005 | title = Direct radiometric dating of hydrocarbon deposits using rhenium-osmium isotopes | journal = Science | volume = 308 | issue = 5726| pages = 1293–1295 | doi=10.1126/science.1111081 | pmid=15919988| bibcode = 2005Sci...308.1293S | s2cid = 41419594 }}</ref> Two smaller but still very large formations occur in the [[Peace River oil sands]] and the [[Cold Lake oil sands]], to the west and southeast of the Athabasca oil sands, respectively. Of the Alberta deposits, only parts of the Athabasca oil sands are shallow enough to be suitable for surface mining. The other 80% has to be produced by oil wells using [[enhanced oil recovery]] techniques like [[steam-assisted gravity drainage]].<ref name=oilsandfacts>{{cite web|title=Facts about Alberta's oil sands and its industry |publisher=Oil Sands Discovery Centre |url=http://history.alberta.ca/oilsands/resources/docs/facts_sheets09.pdf |access-date=19 January 2015 |archive-url=https://web.archive.org/web/20151123024928/http://history.alberta.ca/oilsands/resources/docs/facts_sheets09.pdf |archive-date=23 November 2015 }}</ref>
Much smaller heavy oil or bitumen deposits also occur in the [[Uinta Basin]] in Utah, US. The [[Utah oil sands#Tar Sand Triangle|Tar Sand Triangle]] deposit, for example, is roughly 6% bitumen.<ref name=bunger />
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==History==
===Paleolithic times===
Bitumen use goes back to the [[Middle Paleolithic]], where it was shaped into tool handles or used as an adhesive for attaching stone tools to [[Hafting|hafts]].
The earliest evidence of bitumen use was discovered when archeologists identified bitumen material on [[Levallois technique|Levallois]] flint artefacts that date to about 71,000 years BP at the Umm el Tlel open-air site, located on the northern slope of the Qdeir Plateau in el Kowm Basin in Central Syria.<ref>{{Cite journal |last=Boëda |first=Éric |last2=Bonilauri |first2=Stéphanie |last3=Connan |first3=Jacques |last4=Jarvie |first4=Dan |last5=Mercier |first5=Norbert |last6=Tobey |first6=Mark |last7=Valladas |first7=Hélène |last8=Sakhel |first8=Heba al |date=2008 |title=New Evidence for Significant Use of Bitumen in Middle Palaeolithic Technical Systems at Umm el Tlel (Syria) around 70,000 BP |url=https://www.jstor.org/stable/41496524 |journal=Paléorient |volume=34 |issue=2 |pages=67–83 |issn=0153-9345}}</ref> Microscopic analyses found bituminous residue on two-thirds of the stone artefacts, suggesting that bitumen was an important and frequently-used component of tool making for people in that region at that time. Geochemical analyses of the asphaltic residues places its source to localized natural bitumen outcroppings in the Bichri Massif, about 40 km northeast of the Umm el Tlel archeological site.
A re-examination of artifacts uncovered in 1908 at [[Le Moustier]] rock shelters in France has identified [[Mousterian]] stone tools that were attached to grips made of [[ochre]] and bitumen.<ref>{{Cite journal |last1=Schmidt |first1=Patrick |last2=Iovita |first2=Radu |last3=Charrié-Duhaut |first3=Armelle |last4=Möller |first4=Gunther |last5=Namen |first5=Abay |last6=Dutkiewicz |first6=Ewa |date=2024-02-23 |title=Ochre-based compound adhesives at the Mousterian type-site document complex cognition and high investment |journal=Science Advances |language=en |volume=10 |issue=8 |pages=eadl0822 |doi=10.1126/sciadv.adl0822 |pmid=38381827 |issn=2375-2548|pmc=10881035 |bibcode=2024SciA...10L.822S }}</ref> The grips were formulated with 55% ground [[goethite]] ochre and 45% cooked liquid bitumen to create a moldable putty that hardened into handles. Earlier excavations at Le Moustier prevent conclusive identification of the [[archaeological culture]] and age, but the European Mousterian style of these tools suggests they are associated with [[Neanderthal|Neanderthals]] during the late [[Middle Paleolithic]], between 60,000 and 35,000 years before present. It is the earliest evidence of compound adhesive use in Europe.▼
▲A re-examination of artifacts uncovered in 1908 at [[Le Moustier]] rock shelters in France has identified [[Mousterian]] stone tools that were attached to grips made of [[ochre]] and bitumen.<ref>{{Cite journal |last1=Schmidt |first1=Patrick |last2=Iovita |first2=Radu |last3=Charrié-Duhaut |first3=Armelle |last4=Möller |first4=Gunther |last5=Namen |first5=Abay |last6=Dutkiewicz |first6=Ewa |date=2024-02-23 |title=Ochre-based compound adhesives at the Mousterian type-site document complex cognition and high investment |journal=Science Advances |language=en |volume=10 |issue=8 |pages=eadl0822 |doi=10.1126/sciadv.adl0822 |pmid=38381827 |issn=2375-2548|pmc=10881035 |bibcode=2024SciA...10L.822S }}</ref> The grips were formulated with 55% ground [[goethite]] ochre and 45% cooked liquid bitumen to create a moldable putty that hardened into handles. Earlier, less-careful excavations at Le Moustier prevent conclusive identification of the [[archaeological culture]] and age, but the European Mousterian style of these tools suggests they are associated with [[Neanderthal
===Ancient times===
The use of natural bitumen for [[waterproofing]]
In the [[ancient Near East]], the [[Sumer]]ians used natural bitumen deposits for [[mortar (masonry)|mortar]] between [[brick]]s and stones, to cement parts of carvings, such as eyes, into place, for ship [[caulking]], and for waterproofing.<ref name="Abraham1938" /> The Greek historian [[Herodotus]] said hot bitumen was used as mortar in the walls of [[Babylon]].<ref>Herodotus, Book I, 179</ref>
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In the ancient Far East, natural bitumen was slowly boiled to get rid of the higher [[Fraction (chemistry)|fractions]], leaving a [[thermoplastic]] material of higher molecular weight that, when layered on objects, became hard upon cooling. This was used to cover objects that needed waterproofing,<ref name="Abraham1938" /> such as [[scabbard]]s and other items. [[Statuettes]] of household [[deities]] were also cast with this type of material in Japan, and probably also in China.{{citation needed|date=February 2019}}
In [[North America]], archaeological recovery has indicated that bitumen was sometimes used to adhere stone [[projectile point]]s to wooden shafts.<ref>{{cite journal |
===Continental Europe===
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===Other uses===
[[Asphalt shingle|Roofing shingle]]s and [[Asphalt roll roofing|roll roofing]] account for most of the remaining bitumen consumption. Other uses include cattle sprays, fence-post treatments, and waterproofing for fabrics. Bitumen is used to make [[Japan black]], a [[lacquer]] known especially for its use on iron and steel, and it is also used in paint and marker inks by some exterior paint supply companies to increase the weather resistance and permanence of the paint or ink, and to make the color darker.<ref>{{
==Production==
[[File:Asphalt plant pic.jpg|thumbnail|right|Typical asphalt plant for making asphalt]]
About 164,000,000 tons were produced in 2019. It is obtained as the "heavy" (i.e., difficult to distill) fraction. Material with a [[boiling point]] greater than around 500 °C is considered asphalt. Vacuum distillation separates it from the other components in crude oil (such as [[naphtha]], gasoline and [[Diesel fuel|diesel]]). The resulting material is typically further treated to extract small but valuable amounts of lubricants and to adjust the properties of the material to suit applications. In a [[de-asphalting unit]], the crude bitumen is treated with either [[propane]] or [[butane]] in a [[Supercritical fluid|supercritical]] phase to extract the lighter molecules, which are then separated. Further processing is possible by "blowing" the product: namely reacting it with [[oxygen]]. This step makes the product harder and more viscous.<ref name=UllmannAsph/>
[[File:Stealth Communications laying down asphalt over fiber-optic trench in NYC.jpg|thumb|NYC Internet Provider, [[Stealth Communications]],
Bitumen is typically stored and transported at temperatures around {{convert|150|°C|°F|abbr=on}}. Sometimes [[diesel oil]] or [[kerosene]] are mixed in before shipping to retain liquidity; upon delivery, these lighter materials are separated out of the mixture. This mixture is often called "bitumen feedstock", or BFS. Some [[dump truck]]s route the hot engine exhaust through pipes in the dump body to keep the material warm. The backs of tippers carrying asphalt, as well as some handling equipment, are also commonly sprayed with a releasing agent before filling to aid release. Diesel oil is no longer used as a [[release agent]] due to environmental concerns.
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The report indicates that an "average" 1-mile (1.6-kilometer)-long, four-lane highway would include "300 tons of asphalt," which, "in 2002 would have cost around $48,000. By 2006 this would have increased to $96,000 and by 2012 to $183,000... an increase of about $135,000 for every mile of highway in just 10 years."<ref name="whats_in_your_asphalt_2017_09_fhwa" />
The Middle East is a significant exporter of bitumen, particularly to India and China. According to the Argus Bitumen Report (2024/07/12), India is the largest importer, driven by extensive infrastructure projects. The report projects a CAGR of 4.5% for India's bitumen imports over the next five years, while China's imports are expected to grow at a CAGR of 3.8%. The current export price to India is approximately $350 per metric ton, and for China, it is around $360 per metric ton. The Middle East's strategic advantage in crude oil production underpins its capacity to meet these demands.<ref name="Bitumen Price">{{cite web |title=Growing Demand for Middle Eastern Bitumen Price|url=https://www.gulfrequest.com/post/the-growing-demand-for-middle-eastern-bitumen-in-india-and-china |access-date=25 July 2024}}</ref>
==Health and safety==
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People can be exposed to bitumen in the workplace by breathing in fumes or skin absorption. The [[National Institute for Occupational Safety and Health]] (NIOSH) has set a [[recommended exposure limit]] of 5 mg/m<sup>3</sup> over a 15-minute period.<ref>{{cite web|title = CDC – NIOSH Pocket Guide to Chemical Hazards – Asphalt fumes|url = https://www.cdc.gov/niosh/npg/npgd0042.html|website = cdc.gov|access-date = 27 November 2015}}</ref>
Bitumen is
In 2020, scientists reported that bitumen currently is a significant and largely overlooked source of [[air pollution]] in urban areas, especially during hot and sunny periods.<ref>{{cite news |title=Asphalt adds to air pollution, especially on hot, sunny days |url=https://phys.org/news/2020-09-asphalt-air-pollution-hot-sunny.html |access-date=11 October 2020 |work=phys.org |language=en}}</ref><ref>{{cite journal |last1=Khare |first1=Peeyush |last2=Machesky |first2=Jo |last3=Soto |first3=Ricardo |last4=He |first4=Megan |last5=Presto |first5=Albert A. |last6=Gentner |first6=Drew R. |title=Asphalt-related emissions are a major missing nontraditional source of secondary organic aerosol precursors |journal=Science Advances |date=1 September 2020 |volume=6 |issue=36 |pages=eabb9785 |doi=10.1126/sciadv.abb9785 |pmid=32917599 |pmc=7467703 |bibcode=2020SciA....6.9785K |url=|language=en |issn=2375-2548}}</ref>
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