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Asphalt (or bitumen) is a natural component of most petroleums, in which it
exists in solution. The crude petroleum is refined to separate the various fractions
and recover the asphalt. Similar processes occurring in nature have formed natural
deposits of asphalt.
Asphalt has many uses, as it is a strong cement, readily adhesive, highly waterproof
and durable. It is a plastic substance that imparts controllable flexibility to
mixtures of mineral aggregates with which it is usually combined. It is highly
resistant to the actions of most acids, alkalies and salts. Although a solid or
semi-solid at ordinary atmospheric temperature, asphalt may be readily liquefied
by applying heat, by dissolving it in petroleum solvents of varying volatility,
or by emulsifying it.
HISTORY OF ASPHALT
Prehistoric
Skeletons of prehistoric animals preserved intact to present day in
surface deposits of asphalt. An example would be the La Brea Tar Pit, Los Angeles,
CA, USA.
3200 - 540 BC
Recent archaeological excavations show extensive use of natural asphalt
in Mesopotamia and Indus Valley, as cement for masonry and street construction
and a waterproofing layer for temple baths and water tanks.
300 BC
Asphalt extensively used for mummification in Egypt.
1802 AD
Rock asphalt used in France for floor, bridge and sidewalk surfacing.
1838 AD
Rock asphalt imported and used in sidewalk construction in Philadelphia.
1870 (circa) AD
First asphalt pavement laid in Newark, New Jersey.
1902 AD
Approximately 20,000 tons of asphalt refined from petroleum in the
United States.
Since 1926 AD
The petroleum asphalt and road oil tonnage produced annually has increased steadily
- from 3,000,000 tons in 1926 to 11,000,000 in 1950. Then to more than 30,000,000
tons in 1985. Total worldwide production in 1998 was over 50,000,000 tons.
ASPHALT FROM PETROLEUM
Almost all asphalt used in the world is refined from petroleum. This asphalt
is produced in a variety of final types and grades ranging from hard brittle solids
to almost water-thin liquids. The semi-solid form, known as asphalt cement, is
the basic material.
Some asphalt products are made fluid by emulsifying asphalt cement with water
or by cutting back or blending them with petroleum distillates.
Click here to see some uses and applications of asphalt
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