Asphalt ( ˈæs.fɒlt (help·info)) is a sticky, black and highly viscous liquid or semi-solid that is present in most crude petroleums and in some natural deposits sometimes termed asphaltum. It is most commonly modelled as a colloid, with asphaltenes as the dispersed phase and maltenes as the continuous phase (though there is some disagreement amongst chemists regarding its structure). One writer states that although a "considerable amount of work has been done on the composition of asphalt, it is exceedingly difficult to separate individual hydrocarbon in pure form", and "it is almost impossible to separate and identify all the different molecules of asphalt, because the number of molecules with different chemical structure is extremely large".
In U.S. and Polish terminology, asphalt (or asphalt cement) is the carefully refined residue from the distillation process of selected crude oils. Outside these countries, the product is often called bitumen. Natural deposits terminology also sometimes uses the word bitumin, such as at the La Brea Tar Pits.
The primary use of asphalt is in road construction, where it is used as the glue or binder for the aggregate particles. The road surfacing material is usually called 'asphaltic concrete', AC in North America, or 'asphalt' elsewhere.
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The word asphalt is derived from the late Middle English : from French asphalte, based on Late Latin asphalton, asphaltum, from the Greek ásphalton, ásphaltos (άσφαλτος), a word of uncertain origin meaning "asphalt/bitumen/pitch" which some derive from α- "without" and σφάλλω "to make fall". Note that in French, the term asphalte is used for naturally occurring bitumen-soaked limestone deposits, and for specialised manufactured products with fewer voids or greater bitumen content than the "asphaltic concrete" used to pave roads. Another description has it that the term derives from the Accadian term "asphaltu" or "sphallo," meaning "to split." It was later adopted from the Homeric Greeks as a verb meaning "to make firm or stable," "to secure". It is a significant fact that the first use of asphalt by the ancients was in the nature of a cement for securing or joining together various objects, and it thus seems likely that the name itself was expressive of this application. From the Greek, the word passed into late Latin, and thence into French ("asphalte") and English ("asphalt"). The expression "bitumen" originated in the Sanskrit, where we find the words "jatu," meaning "pitch," and "jatu-krit," meaning "pitch creating," "pitch producing" (referring to coniferous or resinous trees). The Latin equivalent is claimed by some to be originally 'gwitu-men' (pertaining to pitch), and by others, "pixtumens" (exuding or bubbling pitch), which was subsequently shortened to "bitumen," thence passing via French into English. From the same root is derived the Anglo Saxon word "cwidu" (Mastix), the German word "Kitt" (cement or mastic) and the old Norse word "kvada".
Modern usage Edit
In British English, the word 'asphalt' refers to a mixture of mineral aggregate and bitumen (or tarmac in common parlance). The word 'tar' refers to the black viscous material obtained from the destructive distillation of coal and is chemically distinct from bitumen. In American English, bitumen is referred to as 'asphalt' or 'asphalt cement' in engineering jargon. In Australian English, bitumen is sometimes used as the generic term for road surfaces. In Canadian English, the word bitumen is used to refer to the vast Canadian deposits of extremely heavy crude oil, while asphalt is used for the oil refinery product used to pave roads and manufacture roof shingles. Diluted bitumen (diluted with naphtha to make it flow in pipelines) is known as dilbit in the Canadian petroleum industry, while bitumen "upgraded" to synthetic crude oil is known as syncrude and syncrude blended with bitumen as synbit.
Asphalt or bitumen can sometimes be confused with tar, which is a similar black thermo-plastic material produced by the destructive distillation of coal. During the early- and mid-twentieth century when town gas was produced, tar was a readily available product and extensively used as the binder for road aggregates. The addition of tar to macadam roads led to the word tarmac, which is now used in common parlance to refer to road making materials. However, since the 1970s, when natural gas succeeded town gas, asphalt (bitumen) has completely overtaken the use of tar in these applications.
Asphalt can be separated from the other components in crude oil (such as naphtha, gasoline and diesel) by the process of fractional distillation, usually under vacuum conditions. A better separation can be achieved by further processing of the heavier fractions of the crude oil in a de-asphalting unit, which uses either propane or butane in a supercritical phase to dissolve the lighter molecules which are then separated. Further processing is possible by "blowing" the product: namely reacting it with oxygen. This makes the product harder and more viscous.
Natural deposits of asphalt include lake asphalts (primarily from the Pitch Lake in Trinidad and Tobago and Bermudez Lake in Venezuela), Gilsonite, the Dead Sea, and Tar Sands. Asphalt was mined at Ritchie Mines in Macfarlan in Ritchie County, West Virginia in the United States from 1852 to 1873.
Asphalt is typically stored and transported at temperatures around 150 degrees Celsius (300 °F). 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 trucks 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 sometimes used as a release agent, although it can mix with and thereby reduce the quality of the asphalt.
In the ancient Middle East, natural asphalt deposits were used for mortar between bricks and stones, to cement parts of carvings such as eyes into place, for ship caulking, and for waterproofing. The Persian word for asphalt is mumiya, which is related to the English word mummy. Asphalt was also used by ancient Egyptians to embalm mummies. In the ancient Far East, natural asphalt was slowly boiled to get rid of the higher fractions, leaving a material of higher molecular weight which is thermoplastic and when layered on objects, became quite hard upon cooling. This was used to cover objects that needed waterproofing, such as scabbards and other items. Statuettes of household deities were also cast with this type of material in Japan, and probably also in China.
Early use in EuropeEdit
An 1838 edition of Mechanics Magazine cites an early use of asphalt in France. A pamphlet dated 1621, by "a certain Monsieur d'Eyrinys, states that he had discovered the existence (of asphaltum) in large quantities in the vicinity of Neufchatel", and that he proposed to use it in a variety of ways - "principally in the construction of air-proof granaries, and in protecting, by means of the arches, the water-courses in the city of Paris from the intrusin of dirt and filth", which at that time made the water unusable. "He expatiates also on the excellence of this material for forming level and durable terraces" in palaces, "the notion of forming such terraces in the streets not one likely to cross the brain of a Parisian of that generation". But it was generally neglected in France until the revolution of 1830. Then, in the 1830s, there was a surge of interest, and asphalt became widely used "for pavements, flat roofs, and the lining of cisterns, and in England, some use of it had been made of it for similar purposes". Its rise in Europe was "a sudden phenomenon", after natural deposits were found "in France at Osbann (BasRhin), the Parc (l'Ain) and the Puy-de-la-Poix (Puy-de-Dome)", although it could also be made artificially. One of the earliest uses in France was the laying of about 24,000 square yards of Seyssel asphalt at the Place de la Concorde in 1835.
Early use in the United KingdomEdit
In Britain, the first patent was 'Cassell's patent asphalte or bitumen' in 1834. Then on 25 November 1837, Richard Tappin Claridge patented the use of Seyssel asphalt (patent #7849), for use in asphalte pavement, having seen it employed in France and Belgium when visiting with Frederick Walter Simms, who worked with him on the introduction of asphalt to Britain. Dr T. Lamb Phipson claims that his father, Samuel Ryland Phipson, a friend of Claridge, was also "instrumental in introducing the asphalte pavement (in 1836)". Indeed, mastic pavements had been previously employed at Vauxhall by a competitor of Claridge, but without success.
In 1838, Claridge obtained patents in Scotland on 27 March, and Ireland on 23 April, and in 1851 he sought to extend the duration of all three patents. He formed Claridge's Patent Asphalte Company for the purpose of introducing to Britain "Asphalte in its natural state from the mine at Pyrimont Seysell in France", and "laid one of the first asphalt pavements in Whitehall". Trials were made of the pavement in 1838 on the footway in Whitehall, the stable at Knightsbridge Barracks, "and subsequently on the space at the bottom of the steps leading from Waterloo Place to St. James Park". "The formation in 1838 of Claridge's Patent Asphalte Company (with a distinguished list of aristocratic patrons, and Marc and Isambard Brunel as, respectively, a trustee and consulting engineer), gave an enormous impetus to the development of a British asphalt industry". "By the end of 1838, at least two other companies, Robinson's and the Bastenne company, were in production", with asphalt being laid as paving at Brighton, Herne Bay, Canterbury, Kensington, the Strand, and a large floor area in Bunhill-row, while meantime Claridge's Whitehall paving "continue(d) in good order".
Indeed in 1838, there was a flurry of entrepreneurial activity over asphalt, which had uses beyond paving. For example, asphalt could also used for flooring, damp proofing in buildings, and for waterproofing of various types of pools and baths, with these latter themselves proliferating in the 1800s. On the London stockmarket, there were various claims as to the priority of asphalt quality from France, Germany and England. And numerous patents were granted in France, with similar numbers of patent applications being denied in England due to their similarity to each other. In England, "Claridge's was the type most used in the 1840s and 50s" 
In 1914, Claridge's Company entered into a joint venture to produce tar-bound macadam, with materials manufactured through a subsidiary company called Clarmac Roads Ltd. Two products resulted, namely Clarmac, and Clarphalte, with the former being manufactured by Clarmac Roads and the latter by Claridge's Patent Asphalte Co., although Clarmac was more widely used.[a] However, the First World War impacted financially on the Clarmac Company, which entered into liquidation in 1915. The failure of Clarmac Roads Ltd had a flow-on effect to Claridge's Company, which was itself compulsorily wound up, ceasing operations in 1917, having invested a substantial amount of funds into the new venture, both at the outset, and in a subsequent attempt to save the Clarmac Company.
Early use in the United States Edit
The first use of asphaltum in the New World was by indigenous Indian tribes. On the west coast, as early as the 1200s, the Tongva and Chumash Nations collected the naturally occurring asphaltum that seeped to the surface above underlying petroleum deposits. Both tribes used the substance as an adhesive. It is found on many different artifacts of tools and ceremonial items. For example, it was used on rattles to adhere gourds or turtle shells to rattle handles. It was also used in decorations. Small round shell beads were often set in asphatum to provide decorations. It was used as a sealant on baskets to make them water tight for carrying water. Asphaltum was used also to seal the planks on ocean-going canoes.
Roads in the US have been paved with asphalt since at least 1870, when a street in front of Newark, NJ's City Hall was paved. In 1876, asphalt was used to pave Pennsylvania Avenue in Washington, DC, in time for the celebration of the national centennial. Asphalt was also used for flooring, paving and waterproofing of baths and swimming pools during the early 1900s, following similar trends in Europe.
Rolled asphalt concrete Edit
The largest use of asphalt is for making asphalt concrete for road surfaces and accounts for approximately 85% of the asphalt consumed in the United States. Asphalt pavement material is commonly composed of 5 percent asphalt cement and 95 percent aggregates (stone, sand, and gravel). Due to its highly viscous nature, asphalt cement must be heated so that it can be mixed with the aggregates at the asphalt mixing plant. There are about 4,000 asphalt mixing plants in the U.S.
Asphalt road surface is the most widely recycled material in the US, both by gross tonnage and by percentage. According to a report issued by the Federal Highway Administration and the United States Environmental Protection Agency, 80% of the asphalt removed each year from road surfaces during widening and resurfacing projects is reused as part of new roads, roadbeds, shoulders and embankments.
Asphalt is widely used in airports around the world. Due to the sturdiness, it is widely used for runways dedicated to aircraft landing and taking off.
Mastic asphalt Edit
Mastic asphalt is a type of asphalt which differs from dense graded asphalt (asphalt concrete) in that it has a higher bitumen (binder) content, usually around 7–10% of the whole aggregate mix, as opposed to rolled asphalt, which has only around 5% added bitumen. This thermoplastic substance is widely used in the building industry for waterproofing flat roofs and tanking underground. Mastic asphalt is heated to a temperature of 210 °C (410 °F) and is spread in layers to form an impervious barrier about 20 millimeters (0.8 in) thick.
Asphalt emulsion Edit
A number of technologies allow asphalt to be mixed at much lower temperatures. These involve mixing the asphalt with petroleum solvents to form "cutbacks" with reduced melting point or mixtures with water to turn the asphalt into an emulsion. Asphalt emulsions contain up to 70% asphalt and typically less than 1.5% chemical additives. There are two main types of emulsions with different affinity for aggregates, cationic and anionic. Asphalt emulsions are used in a wide variety of applications. Chipseal involves spraying the road surface with asphalt emulsion followed by a layer of crushed rock or gravel. Slurry Seal involves the creation of a mixture of asphalt emulsion and fine crushed aggregate that is spread on the surface of a road. Cold mixed asphalt can also be made from asphalt emulsion to create pavements similar to hot-mixed asphalt, several inches in depth and asphalt emulsions are also blended into recycled hot-mix asphalt to create low cost pavements.
Alternatives and bioasphalt Edit
- Main article: Peak oil
Certain activist groups have become increasingly concerned about the global peak oil and climate change problem in recent years due to by-products that are released into the atmosphere. Most of the emissions are derived primarily from burning fossil fuels. This has led to the introduction of petroleum bitumen alternatives that are more environmentally friendly and non-toxic.
- Lay, Maxwell G (1992), The Ways of the World: A History of the World's Roads and of the Vehicles that Used Them, Rutgers University Press, ISBN 0-8135-2691-4, http://books.google.com.au/books?id=flvS-nJga8QC&printsec=frontcover&dq=%22Ways+of+the+World%22&hl=en&ei=XMYPTNieNYnQcdHOqYoN&sa=X&oi=book_result&ct=result&resnum=1&ved=0CCsQ6AEwAA#v=onepage&q&f=false
a. ^ The Building News and Engineering Journal contains photographs of the following roads where Clarmac was used, being "some amongst many laid with 'Clarmac'": Scott's Lane, Beckenham; Dorset Street, Marylebone; Lordswood Road, Birmingham; Hearsall Lane, Coventry; Valkyrie Avenue, Westcliff-on-Sea; and Lennard Road, Penge.
- ↑ 1.0 1.1 1.2 1.3 1.4 Abraham, Herbert (1938). Asphalts and Allied Substances: Their Occurrence, Modes of Production, Uses in the Arts, and Methods of Testing (4th ed.). New York: D. Van Nostrand Co. http://www.archive.org/details/asphaltsandallie031010mbp. Retrieved 2009-11-16. Full text at Internet Archive (archive.org)
- ↑ Muhammad Abdul Quddus (1992). "Catalytic Oxidation of Asphalt". thesis submitted to Department of Applied Chemistry; University of Karachi. Pakistan: Higher Education Commission Pakistan: Pakistan Research Repository. p. 6, in ch.2 pdf. http://eprints.hec.gov.pk/1171/1/891.html.htm.
- ↑ Muhammad Abdul Quddus (1992), p.99, in ch.5 pdf
- ↑ Liddell, Henry George. "A Greek-English Lexicon". http://artfl.uchicago.edu/cgi-bin/philologic/getobject.pl?c.1:5:73.lsj. Retrieved 2009-02-01.
- ↑ Abraham, Herbert (1938), p.1
- ↑ "What is Oil Sands". Alberta Energy. 2007. http://www.energy.gov.ab.ca/OilSands/793.asp. Retrieved 2008-01-10.
- ↑ "2007 Canadian Crude Oil Forecast and Market Outlook". Canadian Association of Petroleum Producers. June 2007. http://www.capp.ca/default.asp?V_DOC_ID=1220. Retrieved 2008-05-30.
- ↑ Pringle, Heather Anne (2001). The Mummy Congress: Science, Obsession, and the Everlasting Dead. New York, NY: Barnes & Noble Books. pp. 196–197. ISBN 0-7607-7151-0.
- ↑ C.Michael Hogan (2008) Morro Creek, ed. by A. Burnham
- ↑ "Nothing New under the Sun (on French asphaltum use in 1621)". The Mechanic's magazine, museum, register, journal and gazette. 29. London: W.A. Robertson. April 7th-29th September 1838. p. 176. http://books.google.com.au/books?id=ygoAAAAAMAAJ&pg=PA479&lpg=PA479&dq=1838+september+%22mechanic's+magazine%22&source=bl&ots=qtle2WwEjk&sig=kQIkl0cGnEC7Qc466HL2SLMJLSE&hl=en&ei=mjH7Suz_IsqUkAWEmqitCw&sa=X&oi=book_result&ct=result&resnum=2&ved=0CAsQ6AEwAQ#v=onepage&q=asphaltum%20museum&f=false.
- ↑ 11.0 11.1 11.2 11.3 Miles, Lewis (2000). "Section 10.6: Damp Proofing". in Australian Building: A Cultural Investigation. p. 10.06.1. http://www.mileslewis.net/australian-building/pdf/climatic-design/climatic-design-damp-proofing.pdf. Retrieved 2009-11-11. . Note: different sections of Miles' online work were written in different years, as evidenced at the top of each page (not including the heading page of each section). This particular section appears to have been written in 2000
- ↑ 12.0 12.1 R.J. Forbes (1958), Studies in Early Petroleum History, Leiden, Netherlands: E.J. Brill, p. 24, http://books.google.com.au/books?id=eckUAAAAIAAJ&pg=PA24&dq=asphalt+claridge&hl=en&ei=EnURTLy9JI2lcYWSmPAH&sa=X&oi=book_result&ct=result&resnum=7&ved=0CEkQ6AEwBjgK#v=onepage&q=asphalt%20claridge&f=false, retrieved 10 June 2010
- ↑ Salmon, William (1673). Polygraphice; Or, The Arts of Drawing, Engraving, Etching, Limning, Painting, Washing, Varnishing, Gilding, Colouring, Dying, Beautifying and Perfuming. Second Edition.. London: R. Jones. p. 81. http://shipbrook.com/jeff/bookshelf/download.html?bookid=22.
- ↑ "Specification of the Patent granted to Richard Tappin Claridge, of the County of Middlesex, for a Mastic Cement, or Composition applicable to Paving and Road making, covering Buildings and various purposes". Journal of the Franklin Institute of the State of Pennsylvania and Mechanics' Register. Vol. 22. London: Pergamon Press. July 1838 1838. pp. 414–418. http://books.google.com.au/books?id=W8oGAAAAYAAJ&pg=PA414&lpg=PA414&dq=%22richard+tappin+claridge%22&source=bl&ots=8ybZtOzWr6&sig=XaraE45pME1vO6QZW8rUsL7bXMI&hl=en&ei=0nsES8vkHMfykAWX7bzBAQ&sa=X&oi=book_result&ct=result&resnum=3&ved=0CA4Q6AEwAg#v=onepage&q=%22richard%20tappin%20claridge%22&f=false. Retrieved 18 November 2009.
- ↑ "Comments on asphalt patents of R.T. Claridge, Esq". Notes and Queries: A medium of intercommunication for Literary Men, General Readers, etc. Ninth series.. Volume XII, July-December, 1903 (9th S. XII, July 4, 1903). London: John C. Francis. January 20 1904. pp. 18–19. http://www.archive.org/stream/s9notesqueries12londuoft#page/18/mode/2up/search/claridge. Writer is replying to note or query from previous publication, cited as 9th S. xi. 30
- ↑ "Obituary of Frederick Walter Simms". Monthly Notices of the Royal Astronomical Society (London: Strangeways & Walden) XXVI: 120–121. November 1865 - June 1866. http://books.google.co.uk/books?id=3wsAAAAAMAAJ. Retrieved 2009-11-12.
- ↑ Phipson, Dr T. Lamb (1902). Confessions of a Violinist: Realities and Romance. London: Chatto & Windus. p. 11. http://www.archive.org/details/confessionsofvio00phiprich. Retrieved 26 November 2009. Full text at Internet Archive (archive.org)
- ↑ "Claridge's UK Patents in 1837 & 1838". The London Gazette. February 25 1851. p. 489. http://www.london-gazette.co.uk/issues/21185/pages/489.
- ↑ 19.0 19.1 Hobhouse, Hermione (General Editor) (1994). "British History Online". 'Northern Millwall: Tooke Town', Survey of London: volumes 43 and 44: Poplar, Blackwall and Isle of Dogs. pp. 423–433 (see text at refs 169 & 170). http://www.british-history.ac.uk/report.aspx?compid=46514&strquery=Claridge. Retrieved 2009-11-08.
- ↑ "Claridge's Scottish and Irish Patents in 1838". The Mechanic's magazine, museum, register, journal and gazette. 29. London: W.A. Robertson. April 7th-29th September 1838. pp. vii, viii, 64, 128. http://books.google.com.au/books?id=ygoAAAAAMAAJ&pg=PA479&lpg=PA479&dq=1838+september+%22mechanic's+magazine%22&source=bl&ots=qtle2WwEjk&sig=kQIkl0cGnEC7Qc466HL2SLMJLSE&hl=en&ei=mjH7Suz_IsqUkAWEmqitCw&sa=X&oi=book_result&ct=result&resnum=2&ved=0CAsQ6AEwAQ#v=onepage&q=claridge&f=false.
- ↑ 21.0 21.1 "Joint Stock Companies (description of asphalte use by Claridge's company)". The Civil Engineer and Architects Journal. Vol. 1. London. October 1837-December 1838. p. 199. http://www.archive.org/details/civilengineerarc01lond. Retrieved 2009-11-16. Full text at Internet Archive (archive.org). Alternative viewing at: http://books.google.com/books?id=sQ5AAAAAYAAJ&pg
- ↑ Miles, Lewis (2000), pp.10.06.1-2
- ↑ 23.0 23.1 Comments on asphalt patents of R.T. Claridge, Esq (1904), p.18
- ↑ 24.0 24.1 Miles, Lewis (2000), p.10.06.2
- ↑ "1838 bitumen UK uses by Robinson's and Claridge's companies, & the Bastenne company". The Mechanic's magazine, museum, register, journal and gazette. 29. London: W.A. Robertson. 22nd September 1838. p. 448. http://books.google.com.au/books?id=ygoAAAAAMAAJ&pg=PA479&lpg=PA479&dq=1838+september+%22mechanic's+magazine%22&source=bl&ots=qtle2WwEjk&sig=kQIkl0cGnEC7Qc466HL2SLMJLSE&hl=en&ei=mjH7Suz_IsqUkAWEmqitCw&sa=X&oi=book_result&ct=result&resnum=2&ved=0CAsQ6AEwAQ#v=onepage&q=bastenne&f=false.
- ↑ 26.0 26.1 Gerhard, W.M. Paul (1908). Modern Baths and Bath Houses (1st ed.). New York: John Wiley and Sons. http://www.archive.org/stream/modernbathsandb00unkngoog#page/n11/mode/1up. (Enter "asphalt" into the search field for list of pages discussing the subject)
- ↑ "Claridge's Patent Asphalte Co. ventures into tarred slag macadam", Concrete and Constructional Engineering (London) IX (1): 760, January 1914, http://www.archive.org/stream/concreteconstruc09lond#page/760/mode/1up, retrieved 15 June 2010
- ↑ "Registration of Clarmac Roads", The Law Reports: Chancery Division Vol. 1: 544-547, 1921, http://books.google.com/books?id=2AQxAAAAIAAJ&q=clarmac&dq=clarmac&hl=en&ei=w6waTM6tNZKXcdjQyIMK&sa=X&oi=book_result&ct=result&resnum=4&ved=0CDEQ6AEwAw, retrieved 17 June 2010
- ↑ "Clarmac and Clarphalte", The Building News and Engineering Journal Vol. 109: July to December 1915 (No. 3157): pp.2-4 (n13-15 in electronic page field), July 7 1915, http://www.archive.org/stream/buildingnewseng109londuoft#page/n13/mode/1up/search/clarmac, retrieved 18 June 2010
- ↑ 30.0 30.1 Clarmac financial difficults due to WW1 Debentures deposited The Law Reports: Chancery Division, (1921) Vol. 1 p.545. Retrieved 17 June 2010.
- ↑ "Notice of the Winding up of Clarmac Roads", The London Gazette (29340): 10568, 26 October 1915, http://www.london-gazette.co.uk/issues/29340/pages/10568, retrieved 15 June 2010
- ↑ 32.0 32.1 Claridge's Patent Asphalte Co. compulsorily wound up Funds invested in new company The Law Times Reports (1921) Vol.125, p.256. Retrieved 15 June 2010.
- ↑ "Claridge's Patent Asphalte Co. winds up 10 November 1917". The London Gazette. 16 November 1917. p. 11863. http://www.london-gazette.co.uk/issues/30384/pages/11863.
- ↑ Hobhouse, Hermione (General Editor) (1994). "British History Online". 'Cubitt Town: Riverside area: from Newcastle Drawdock to Cubitt Town Pier', Survey of London: volumes 43 and 44: Poplar, Blackwall and Isle of Dogs. pp. 528–532 (see text at refs 507 & 510). http://www.british-history.ac.uk/report.aspx?compid=46529&strquery=claridge. Retrieved 2009-11-08.
- ↑ McNichol, Dan (2005). Paving the Way: Asphalt in America. Lanham, MD: National Asphalt Pavement Association. ISBN 0-914313-04-5. http://store.hotmix.org/index.php?productID=144.
- ↑ Roads laid with Clarmac The Building News and Engineering Journal, 1915 109 (3157), p.3 (n14 in electronic field).
- Barth, Edwin J., Asphalt: Science and Technology Gordon and Breach (1962). ISBN 0-677-00040-5.
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