Asphalt, also known as bitumen (UK: /ˈbɪtʃəmən/, US:
/bɪˈtjuːmən, baɪ-/), is a sticky, black, and highly viscous
liquid or semi-solid form of petroleum. It may be found in natural
deposits or may be a refined product, and is classed as a pitch.
Before the 20th century, the term asphaltum was also used. The word
is derived from the
Ancient Greek ἄσφαλτος ásphaltos.
The primary use (70%) of asphalt is in road construction, where it is
used as the glue or binder mixed with aggregate particles to create
asphalt concrete. Its other main uses are for bituminous waterproofing
products, including production of roofing felt and for sealing flat
The terms "asphalt" and "bitumen" are often used interchangeably to
mean both natural and manufactured forms of the substance. In American
English, "asphalt" (or "asphalt cement") is commonly used for a
refined residue from the distillation process of selected crude oils.
Outside the United States, the product is often called "bitumen", and
geologists worldwide often prefer the term for the naturally occurring
variety. Common colloquial usage often refers to various forms of
asphalt as "tar", as in the name of the La Brea
Naturally occurring asphalt is sometimes specified by the term "crude
bitumen". Its viscosity is similar to that of cold molasses
while the material obtained from the fractional distillation of crude
oil boiling at 525 °C (977 °F) is sometimes referred to as
"refined bitumen". The Canadian province of
Alberta has most of the
world's reserves of natural asphalt in the Athabasca oil sands, which
cover 142,000 square kilometres (55,000 sq mi), an area
larger than England.
1.2 Modern terminology
4.1 Ancient times
4.2 Continental Europe
4.3 United Kingdom
4.4 United States
4.6 Photography and art
5 Modern use
5.1 Global use
5.2 Rolled asphalt concrete
5.3 Mastic asphalt
Synthetic crude oil
5.6 Non-upgraded crude bitumen
5.7 Radioactive waste encapsulation matrix
5.8 Other uses
6.1 Oil sands
6.2 Alternatives and bioasphalt
6.3 Albanian deposits
7 Health and safety
8 See also
12 External links
The word "asphalt" is derived from the late Middle English, in turn
from French asphalte, based on
Late Latin asphalton, asphaltum, which
is the latinisation of the Greek ἄσφαλτος (ásphaltos,
ásphalton), a word meaning "asphalt/bitumen/pitch", which perhaps
derives from ἀ-, "without" and σφάλλω (sfallō), "make
fall". 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
Herodotus mentioned that bitumen was
Babylon to build its gigantic fortification wall. From
the Greek, the word passed into late Latin, and thence into French
(asphalte) and English ("asphaltum" and "asphalt"). In French, the
term asphalte is used for naturally occurring asphalt-soaked limestone
deposits, and for specialised manufactured products with fewer voids
or greater bitumen content than the "asphaltic concrete" used to pave
The expression "bitumen" originated in the
Sanskrit words jatu,
meaning "pitch", and jatu-krit, meaning "pitch creating" or "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
In British English, "bitumen" is used instead of "asphalt". The word
"asphalt" is instead used to refer to asphalt concrete, a mixture of
construction aggregate and asphalt itself (also called "tarmac" in
Bitumen mixed with clay was usually called
"asphaltum", but the term is less commonly used today.[citation
In Australian English, "bitumen" is often used as the generic term for
In American English, "asphalt" is equivalent to the British "bitumen".
However, "asphalt" is also commonly used as a shortened form of
"asphalt concrete" (therefore equivalent to the British "asphalt" or
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. 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 is
"Bitumen" is still the preferred geological term for naturally
occurring deposits of the solid or semi-solid form of petroleum.
"Bituminous rock" is a form of sandstone impregnated with bitumen. The
tar sands of
Alberta, Canada are a similar material.
Neither of the terms "asphalt" or "bitumen" should be confused with
tar or coal tars.[further explanation needed]
See also: Asphaltene
The components of asphalt 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 acids 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
The naphthene aromatics and polar aromatics are typically the majority
components. Most natural bitumens also contain organosulfur compounds,
resulting in an overall sulfur content of up to 4%.
vanadium are found at <10 parts per million, as is typical of some
The substance is soluble in carbon disulfide. It is commonly modelled
as a colloid, with asphaltenes as the dispersed phase and maltenes as
the continuous phase. "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".
Asphalt may be confused with coal tar, which is a visually similar
black, thermoplastic material produced by the destructive distillation
of coal. During the early and mid-20th century, when town gas was
produced, coal tar was a readily available byproduct and extensively
used as the binder for road aggregates. The addition of coal 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 has completely overtaken
the use of coal tar in these applications. Other examples of this
confusion include the La Brea
Tar Pits and the Canadian oil sands,
both of which actually contain natural bitumen rather than tar.
"Pitch" is another term sometimes informally used at times to refer to
asphalt, as in Pitch Lake.
Bituminous outcrop of the Puy de la Poix, Clermont-Ferrand, France
The majority of asphalt used commercially is obtained from
petroleum. Nonetheless, large amounts of asphalt occur in
concentrated form in nature. Naturally occurring deposits of bitumen
are formed from the remains of ancient, microscopic algae (diatoms)
and other once-living things. These remains were deposited in the mud
on the bottom of the ocean or lake where the organisms lived. Under
the heat (above 50 °C) and pressure of burial deep in the earth,
the remains were transformed into materials such as bitumen, kerogen,
Natural deposits of bitumen include lakes such as the
Pitch Lake in
Trinidad and Tobago and
Lake Bermudez in Venezuela. Natural seeps
occur in the La Brea
Tar Pits and in the Dead Sea.
Bitumen also occurs in unconsolidated sandstones known as "oil sands"
in Alberta, Canada, and the similar "tar sands" in Utah, US. The
Canadian province of
Alberta has most of the world's reserves, in
three huge deposits covering 142,000 square kilometres
(55,000 sq mi), an area larger than
England or New York
state. These bituminous sands contain 166 billion barrels
(26.4×10^9 m3) 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 refineries in Canada
and the United States.
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 lenses of oil-bearing sand with up to 20% oil. Isotopic
studies show the oil deposits to be about 110 million years old.
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
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
Much smaller heavy oil or bitumen deposits also occur in the Uinta
Basin in Utah, US. The
Sand Triangle deposit, for example, is
roughly 6% bitumen.
Bitumen may occur in hydrothermal veins. An example of this is within
Uinta Basin of Utah, in the US, where there is a swarm of
laterally and vertically extensive veins composed of a solid
hydrocarbon termed Gilsonite. These veins formed by the polymerization
and solidification of hydrocarbons that were mobilized from the deeper
oil shales of the
Green River Formation
Green River Formation during burial and
Bitumen is similar to the organic matter in carbonaceous
meteorites. However, detailed studies have shown these materials
to be distinct. The vast
Alberta bitumen resources are considered
to have started out as living material from marine plants and animals,
mainly algae, that died millions of years ago when an ancient ocean
covered Alberta. They were covered by mud, buried deeply over time,
and gently cooked into oil by geothermal heat at a temperature of 50
to 150 °C (120 to 300 °F). Due to pressure from the rising
Rocky Mountains in southwestern Alberta, 80 to 55 million years
ago, the oil was driven northeast hundreds of kilometres and trapped
into underground sand deposits left behind by ancient river beds and
ocean beaches, thus forming the oil sands.
The use of natural bitumen for waterproofing, and as an adhesive dates
at least to the fifth millennium BC, with a crop storage basket
discovered in Mehrgarh, of the Indus Valley Civilization, lined with
it. By the 3rd millennia BC refined rock asphalt was in use, in
the region, and was used to waterproof the Great Bath, Mohenjo-daro.
In the ancient Middle East, the Sumerians used natural bitumen
deposits for mortar between bricks and stones, to cement parts of
carvings, such as eyes, into place, for ship caulking, and for
waterproofing. The Greek historian
Herodotus said hot bitumen was
used as mortar in the walls of Babylon.
The 1 kilometre (0.62 mi) long
Euphrates Tunnel beneath the river
Babylon in the time of Queen
Semiramis (ca. 800 BC) was
reportedly constructed of burnt bricks covered with bitumen as a
Bitumen was used by ancient Egyptians to embalm mummies. The
Persian word for asphalt is moom, which is related to the English word
mummy. The Egyptians' primary source of bitumen was the Dead Sea,
which the Romans knew as Palus Asphaltites (
Approximately 40 AD,
Dioscorides described the
Dead Sea material as
Judaicum bitumen, and noted other places in the region where it could
be found. The Sidon bitumen is thought to refer to material found
at Hasbeya. Pliny refers also to bitumen being found in Epirus. It
was a valuable strategic resource, the object of the first known
battle for a hydrocarbon deposit—between the Seleucids and the
Nabateans in 312 BC.
In the ancient Far East, natural bitumen was slowly boiled to get rid
of the higher fractions, leaving a thermoplastic material of higher
molecular weight that 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 North America, archaeological recovery has indicated bitumen was
sometimes used to adhere stone projectile points to wooden shafts.
In Canada, aboriginal people used bitumen seeping out of the banks of
the Athabasca and other rivers to waterproof birch bark canoes, and
also heated it in smudge pots to ward off mosquitoes in the
Pierre Belon described in his work Observations that
pissasphalto, a mixture of pitch and bitumen, was used in the Republic
of Ragusa (now Dubrovnik, Croatia) for tarring of ships.
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 intrusion 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
But the substance was generally neglected in France until the
revolution of 1830. 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 (Bas-Rhin), the Parc
(Ain) and the Puy-de-la-Poix (Puy-de-Dôme)", 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.
Among the earlier uses of bitumen in the United Kingdom was for
etching. William Salmon's Polygraphice (1673) provides a recipe for
varnish used in etching, consisting of three ounces of virgin wax, two
ounces of mastic, and one ounce of asphaltum. By the fifth edition
in 1685, he had included more asphaltum recipes from other
The first British patent for the use of asphalt 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 writes 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
Vauxhall by a competitor of Claridge, but without
Claridge obtained a patent in Scotland on 27 March 1838, and obtained
a patent in Ireland on 23 April 1838. In 1851, extensions for the 1837
patent and for both 1838 patents were sought by the trustees of a
company previously formed by Claridge. Claridge's
Patent Asphalte Company—formed in 1838 for the purpose of
introducing to Britain "Asphalte in its natural state from the mine at
Pyrimont Seysell in France",—"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".
In 1838, there was a flurry of entrepreneurial activity involving
asphalt, which had uses beyond paving. For example, asphalt could also
be used for flooring, damp proofing in buildings, and for
waterproofing of various types of pools and baths, both of which were
also proliferating in the 19th century. On the London
stockmarket, there were various claims as to the exclusivity 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.[note 1]
First World War
First World War ruined 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
The first use of bitumen in the New World was by indigenous peoples.
On the west coast, as early as the 13th century, the Tongva, Luiseño
and Chumash peoples collected the naturally occurring bitumen that
seeped to the surface above underlying petroleum deposits. All three
groups 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 asphaltum to provide decorations. It was used as a sealant on
baskets to make them watertight for carrying water, possibly poisoning
those who drank the water.
Asphalt was used also to seal the
planks on ocean-going canoes.
Asphalt was first used to pave streets in the 1870s. At first
naturally occurring "bituminous rock" was used, such as at Ritchie
Mines in Macfarlan in
Ritchie County, West Virginia
Ritchie County, West Virginia from 1852 to 1873.
In 1876, asphalt-based paving was used to pave Pennsylvania Avenue in
Washington DC, in time for the celebration of the national
centennial. In the horse-drawn era, streets were unpaved and
covered with dirt or gravel. However, that produced uneven wear,
opened new hazards for pedestrians and made for dangerous potholes for
bicycles and for motor vehicles. Manhattan alone had 130,000 horses in
1900, pulling streetcars, wagons, and carriages, and leaving their
waste behind. They were not fast, and pedestrians could dodge and
scramble their way across the crowded streets. Small towns continued
to rely on dirt and gravel, but larger cities wanted much better
streets. They looked to wood or granite blocks by the 1850s. In
1890, a third of Chicago's 2000 miles of streets were paved, chiefly
with wooden blocks, which gave better traction than mud. Brick
surfacing was a good compromise, but even better was asphalt paving,
which was easy to install and to cut through to get at sewers. With
London and Paris serving as models, Washington laid 400,000 square
yards of asphalt paving by 1882; it became the model for Buffalo,
Philadelphia and elsewhere. By the end of the century, American cities
boasted 30 million square yards of asphalt paving, well ahead of
brick. The streets became faster and more dangerous so electric
traffic lights were installed. Electric trolleys (at 12 miles per
hour) became the main transportation service for middle class shoppers
and office workers until they bought automobiles after 1945 and
commuted from more distant suburbs in privacy and comfort on asphalt
Bitumount and History of the petroleum industry in Canada
(oil sands and heavy oil)
Canada has the world's largest deposit of natural bitumen in the
Athabasca oil sands, and Canadian
First Nations along the Athabasca
River had long used it to waterproof their canoes. In 1719, a Cree
named Wa-Pa-Su brought a sample for trade to
Henry Kelsey of the
Hudson’s Bay Company, who was the first recorded European to see it.
However, it wasn't until 1787 that fur trader and explorer Alexander
MacKenzie saw the
Athabasca oil sands
Athabasca oil sands and said, "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."
The value of the deposit was obvious from the start, but the means of
extracting the bitumen was not. The nearest town, Fort McMurray,
Alberta, was a small fur trading post, other markets were far away,
and transportation costs were too high to ship the raw bituminous sand
for paving. In 1915, Sidney Ells of the Federal Mines Branch
experimented with separation techniques and used the product to pave
600 feet of road in Edmonton, Alberta. Other roads in
paved with material extracted from oil sands, but it was generally not
economic. During the 1920s Dr. Karl A. Clark of the
Council patented a hot water oil separation process and entrepreneur
Robert C. Fitzsimmons built the
Bitumount oil separation plant,
which between 1925 and 1958 produced up to 300 barrels (50 m3)
per day of bitumen using Dr. Clark's method. Most of the bitumen was
used for waterproofing roofs, but other uses included fuels,
lubrication oils, printers ink, medicines, rust- and acid-proof
paints, fireproof roofing, street paving, patent leather, and fence
post preservatives. Eventually Fitzsimmons ran out of money and
the plant was taken over by the
Alberta government. Today the
Bitumount plant is a Provincial Historic Site.
Photography and art
Bitumen was used in early photographic technology. In 1826 or 1827, it
was used by French scientist
Joseph Nicéphore Niépce
Joseph Nicéphore Niépce to make the
oldest surviving photograph from nature. The bitumen was thinly coated
onto a pewter plate which was then exposed in a camera. Exposure to
light hardened the bitumen and made it insoluble, so that when it was
subsequently rinsed with a solvent only the sufficiently light-struck
areas remained. Many hours of exposure in the camera were required,
making bitumen impractical for ordinary photography, but from the
1850s to the 1920s it was in common use as a photoresist in the
production of printing plates for various photomechanical printing
Bitumen was the nemesis of many artists during the 19th century.
Although widely used for a time, it ultimately proved unstable for use
in oil painting, especially when mixed with the most common diluents,
such as linseed oil, varnish and turpentine. Unless thoroughly
diluted, bitumen never fully solidifies and will in time corrupt the
other pigments with which it comes into contact. The use of bitumen as
a glaze to set in shadow or mixed with other colors to render a darker
tone resulted in the eventual deterioration of many paintings, for
instance those of Delacroix. Perhaps the most famous example of the
destructiveness of bitumen is Théodore Géricault's Raft of the
Medusa (1818–1819), where his use of bitumen caused the brilliant
colors to degenerate into dark greens and blacks and the paint and
canvas to buckle.
The vast majority of refined asphalt is used in construction:
primarily as a constituent of products used in paving and roofing
applications. According to the requirements of the end use, asphalt is
produced to specification. This is achieved either by refining or
blending. It is estimated that the current world use of asphalt is
approximately 102 million tonnes per year. Approximately 85% of all
the asphalt produced is used as the binder in asphalt concrete for
roads. It is also used in other paved areas such as airport runways,
car parks and footways. Typically, the production of asphalt concrete
involves mixing fine and coarse aggregates such as sand, gravel and
crushed rock with asphalt, which acts as the binding agent. Other
materials, such as recycled polymers (e.g., rubber tyres), may be
added to the asphalt to modify its properties according to the
application for which the asphalt is ultimately intended.
A further 10% of global asphalt production is used in roofing
applications, where its waterproofing qualities are invaluable. The
remaining 5% of asphalt is used mainly for sealing and insulating
purposes in a variety of building materials, such as pipe coatings,
carpet tile backing and paint.
Asphalt is applied in the construction
and maintenance of many structures, systems, and components, such as
Footways and pedestrian ways
Reservoir and pool linings
Building water proofing
Tile underlying waterproofing
Newspaper ink production
and many other applications
Rolled asphalt concrete
The largest use of asphalt is for making asphalt concrete for road
surfaces; this accounts for approximately 85% of the asphalt consumed
in the United States.
Asphalt concrete pavement mixes are typically
composed of 5% asphalt cement and 95% aggregates (stone, sand, and
gravel). Due to its highly viscous nature, asphalt cement must be
heated so it can be mixed with the aggregates at the asphalt mixing
facility. The temperature required varies depending upon
characteristics of the asphalt and the aggregates, but warm-mix
asphalt technologies allow producers to reduce the temperature
required. There are about 4,000 asphalt concrete mixing plants in the
US, and a similar number in Europe.
When maintenance is performed on asphalt pavements, such as milling to
remove a worn or damaged surface, the removed material can be returned
to a facility for processing into new pavement mixtures. The asphalt
in the removed material can be reactivated and put back to use in new
pavement mixes. With some 95% of paved roads being constructed of
or surfaced with asphalt, a substantial amount of asphalt pavement
material is reclaimed each year. According to industry surveys
conducted annually by the
Federal Highway Administration
Federal Highway Administration and the
Asphalt Pavement Association, more than 99% of the asphalt
removed each year from road surfaces during widening and resurfacing
projects is reused as part of new pavements, roadbeds, shoulders and
Asphalt concrete paving is widely used in airports around the world.
Due to the sturdiness and ability to be repaired quickly, it is widely
used for runways.
Further information: Fibre mastic asphalt
Mastic asphalt is a type of asphalt that differs from dense graded
asphalt (asphalt concrete) in that it has a higher asphalt (binder)
content, usually around 7–10% of the whole aggregate mix, as opposed
to rolled asphalt concrete, which has only around 5% asphalt. 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
A number of technologies allow asphalt to be mixed at much lower
temperatures. These involve mixing with petroleum solvents to form
"cutbacks" with reduced melting point or mixing 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
Asphalt emulsions are used in a wide variety of
Chipseal involves spraying the road surface with asphalt
emulsion followed by a layer of crushed rock, gravel or crushed slag.
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.
Synthetic crude oil
Synthetic crude oil
Petroleum production in Canada
Synthetic crude oil, also known as syncrude, is the output from a
bitumen upgrader facility used in connection with oil sand production
in Canada. Bituminous sands are mined using enormous (100 ton
capacity) power shovels and loaded into even larger (400 ton capacity)
dump trucks for movement to an upgrading facility. The process used to
extract the bitumen from the sand is a hot water process originally
developed by Dr. Karl Clark of the University of
Alberta during the
1920s. After extraction from the sand, the bitumen is fed into a
bitumen upgrader which converts it into a light crude oil equivalent.
This synthetic substance is fluid enough to be transferred through
conventional oil pipelines and can be fed into conventional oil
refineries without any further treatment. By 2015 Canadian bitumen
upgraders were producing over 1 million barrels (160×10^3 m3)
per day of synthetic crude oil, of which 75% was exported to oil
refineries in the United States.
In Alberta, five bitumen upgraders produce synthetic crude oil and a
variety of other products: The
Suncor Energy upgrader near Fort
Alberta produces synthetic crude oil plus diesel fuel; the
Syncrude Canada, Canadian Natural Resources, and
Nexen upgraders near
Fort McMurray produce synthetic crude oil; and the Shell Scotford
Upgrader near Edmonton produces synthetic crude oil plus an
intermediate feedstock for the nearby Shell Oil Refinery. A sixth
upgrader, under construction in 2015 near Redwater, Alberta, will
upgrade half of its crude bitumen directly to diesel fuel, with the
remainder of the output being sold as feedstock to nearby oil
refineries and petrochemical plants.
Non-upgraded crude bitumen
See also: Western Canadian Select
Canadian bitumen does not differ substantially from oils such as
Venezuelan extra-heavy and Mexican heavy oil in chemical composition,
and the real difficulty is moving the extremely viscous bitumen
through oil pipelines to the refinery. Many modern oil refineries are
extremely sophisticated and can process non-upgraded bitumen directly
into products such as gasoline, diesel fuel, and refined asphalt
without any preprocessing. This is particularly common in areas such
as the US Gulf coast, where refineries were designed to process
Venezuelan and Mexican oil, and in areas such as the US
refineries were rebuilt to process heavy oil as domestic light oil
production declined. Given the choice, such heavy oil refineries
usually prefer to buy bitumen rather than synthetic oil because the
cost is lower, and in some cases because they prefer to produce more
diesel fuel and less gasoline. By 2015 Canadian production and
exports of non-upgraded bitumen exceeded that of synthetic crude oil
at over 1.3 million barrels (210×10^3 m3) per day, of which
about 65% was exported to the United States.
Because of the difficulty of moving crude bitumen through pipelines,
non-upgraded bitumen is usually diluted with natural-gas condensate in
a form called dilbit or with synthetic crude oil, called synbit.
However, to meet international competition, much non-upgraded bitumen
is now sold as a blend of multiple grades of bitumen, conventional
crude oil, synthetic crude oil, and condensate in a standardized
benchmark product such as Western Canadian Select. This sour, heavy
crude oil blend is designed to have uniform refining characteristics
to compete with internationally marketed heavy oils such as Mexican
Mayan or Arabian Dubai Crude.
Radioactive waste encapsulation matrix
Asphalt was used starting in the 1960s as an hydrophobic matrix aiming
to encapsulate radioactive waste such as medium-activity salts (mainly
soluble sodium nitrate and sodium sulfate) produced by the
reprocessing of spent nuclear fuels or radioactive sludges from
sedimentation ponds. Bituminised radioactive waste containing
highly radiotoxic alpha-emitting transuranic elements from nuclear
reprocessing plants have been produced at industrial scale in France,
Belgium and Japan, but this type of waste conditioning has been
abandoned because operational safety issues (risks of fire, as
occurred in a bituminisation plant at Tokai Works in Japan)
and long-term stability problems related to their geological disposal
in deep rock formations. One of the main problem is the swelling of
asphalt exposed to radiation and to water.
Asphalt swelling is first
induced by radiation because of the presence of hydrogen gas bubbles
generated by alpha and gamma radiolysis. A second mechanism is
the matrix swelling when the encapsulated hygroscopic salts exposed to
water or moisture start to rehydrate and to dissolve. The high
concentration of salt in the pore solution inside the bituminised
matrix is then responsible for osmotic effects inside the bituminised
matrix. The water moves in the direction of the concentrated salts,
the asphalt acting as a semi-permeable membrane. This also causes the
matrix to swell. The swelling pressure due to osmotic effect under
constant volume can be as high as 200 bar. If not properly managed,
this high pressure can cause fractures in the near field of a disposal
gallery of bituminised medium-level waste. When the bituminised matrix
has been altered by swelling, encapsulated radionuclides are easily
leached by the contact of ground water and released in the geosphere.
The high ionic strength of the concentrated saline solution also
favours the migration of radionuclides in clay host rocks. The
presence of chemically reactive nitrate can also affect the redox
conditions prevailing in the host rock by establishing oxidizing
conditions, preventing the reduction of redox-sensitive radionuclides.
Under their higher valences, radionuclides of elements such as
selenium, technetium, uranium, neptunium and plutonium have a higher
solubility and are also often present in water as non-retarded anions.
This makes the disposal of medium-level bituminised waste very
Different type of asphalt have been used: blown bitumen (partly
oxidized with air oxygen at high temperature after distillation, and
harder) and direct distillation bitumen (softer). Blown bitumens like
Mexphalte, with a high content of saturated hydrocarbons, are more
easily biodegraded by microorganisms than direct distillation bitumen,
with a low content of saturated hydrocarbons and a high content of
Concrete encapsulation of radwaste is presently considered a safer
alternative by the nuclear industry and the waste management
Roofing shingles account for most of the remaining asphalt
consumption. Other uses include cattle sprays, fence-post treatments,
and waterproofing for fabrics.
Asphalt 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.
Asphalt is also used to seal some
alkaline batteries during the manufacturing process.
Typical asphalt plant for making asphalt
About 40,000,000 tons were produced in 1984.[needs update] 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). 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
asphalt is treated with either propane or butane in a 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
Asphalt is typically stored and transported at temperatures around
150 °C (302 °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 no longer used as a release
agent due to environmental concerns.
Main article: Oil sands
Naturally occurring crude bitumen impregnated in sedimentary rock is
the prime feed stock for petroleum production from "oil sands",
currently under development in Alberta, Canada. Canada has most of the
world's supply of natural bitumen, covering 140,000 square
kilometres (an area larger than England), giving it the
second-largest proven oil reserves in the world. The Athabasca oil
sands are the largest bitumen deposit in Canada and the only one
accessible to surface mining, although recent technological
breakthroughs have resulted in deeper deposits becoming producible by
in situ methods. Because of oil price increases after 2003, producing
bitumen became highly profitable, but as a result of the decline after
2014 it became uneconomic to build new plants again. By 2014, Canadian
crude bitumen production averaged about 2.3 million barrels
(370,000 m3) per day and was projected to rise to 4.4 million
barrels (700,000 m3) per day by 2020. The total amount of
crude bitumen in
Alberta that could be extracted is estimated to be
about 310 billion barrels (50×10^9 m3), which at a rate of
4,400,000 barrels per day (700,000 m3/d) would last about 200
Alternatives and bioasphalt
Main articles: Peak oil, Global warming, and Bioasphalt
Although uncompetitive economically, asphalt can be made from
nonpetroleum-based renewable resources such as sugar, molasses and
rice, corn and potato starches.
Asphalt can also be made from waste
material by fractional distillation of used motor oil, which is
sometimes otherwise disposed of by burning or dumping into landfills.
Use of motor oil may cause premature cracking in colder climates,
resulting in roads that need to be repaved more frequently.
Nonpetroleum-based asphalt binders can be made light-colored.
Lighter-colored roads absorb less heat from solar radiation, reducing
their contribution to the urban heat island effect. Parking lots
that use asphalt alternatives are called green parking lots.
Selenizza is a naturally occurring solid hydrocarbon bitumen found in
native deposits in Selenice, in Albania, the only European asphalt
mine still in use. The bitumen is found in the form of veins, filling
cracks in a more or less horizontal direction. The bitumen content
varies from 83% to 92% (soluble in carbon disulphide), with a
penetration value near to zero and a softening point (ring and ball)
around 120 °C. The insoluble matter, consisting mainly of silica
ore, ranges from 8% to 17%.
Albanian bitumen extraction has a long history and was practiced in an
organized way by the Romans. After centuries of silence, the first
mentions of Albanian bitumen appeared only in 1868, when the Frenchman
Coquand published the first geological description of the deposits of
Albanian bitumen. In 1875, the exploitation rights were granted to the
Ottoman government and in 1912, they were transferred to the Italian
company Simsa. Since 1945, the mine was exploited by the Albanian
government and from 2001 to date, the management passed to a French
company, which organized the mining process for the manufacture of the
natural bitumen on an industrial scale.
Today the mine is predominantly exploited in an open pit quarry but
several of the many underground mines (deep and extending over several
km) still remain viable. Selenizza is produced primarily in granular
form, after melting the bitumen pieces selected in the mine.
Selenizza is mainly used as an additive in the road construction
sector. It is mixed with traditional asphalt to improve both the
viscoelastic properties and the resistance to ageing. It may be
blended with the hot asphalt in tanks, but its granular form allows it
to be fed in the mixer or in the recycling ring of normal asphalt
plants. Other typical applications include the production of mastic
asphalts for sidewalks, bridges, car-parks and urban roads as well as
drilling fluid additives for the oil and gas industry. Selenizza is
available in powder or in granular material of various particle sizes
and is packaged in sacks or in thermal fusible polyethylene bags.
A life-cycle assessment study of the natural selenizza compared with
petroleum asphalt has shown that the environmental impact of the
selenizza is about half the impact of the road asphalt produced in oil
refineries in terms of carbon dioxide emission.
Health and safety
People can be exposed to asphalt 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/m3 over a 15-minute period.
Asphalt is basically an inert material that must be heated or diluted
to a point where it becomes workable for the production of materials
for paving, roofing, and other applications. In examining the
potential health hazards associated with asphalt, the International
Agency for Research on Cancer (IARC) determined that it is the
application parameters, predominantly temperature, that affect
occupational exposure and the potential bioavailable carcinogenic
hazard/risk of the asphalt emissions. In particular, temperatures
greater than 199 °C (390 °F), were shown to produce a
greater exposure risk than when asphalt was heated to lower
temperatures, such as those typically used in asphalt pavement mix
production and placement. IARC has classified asphalt as a Class
2B possible carcinogen.
An asphalt mixing plant for hot aggregate
Cooper Research Technology
Edward de Smedt
International Grooving & Grinding Association
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Wikimedia Commons has media related to Bitumen.
Wikimedia Commons has media related to Asphalt.
Look up asphalt in Wiktionary, the free dictionary.
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