The Open Road, Courtesy of Asphalt
America's way of life. There are approximately 4 million miles or roads, streets and
highways across the United States, tying it all together in a big transportation network.
Asphalt layers cover the roads and parking lots, but what is asphalt really?
It is a product of petroleum. It is a solid substance found on the surface of the earth
and occurs in natural deposits in lakes and rocks. Asphalt is thermoplastic, meaning that
it softens and liquefies when heated and becomes solid again when cooled.
Known uses for asphalt go as far back as six thousand years. Archaeologists have
established that asphalt is one of the oldest adhesives known to man. It was used to make
bathing pools, reservoirs, and canals watertight.
Asphalt was used in Mesopotamia (now known as Iraq). Bricks for the great wall of Babylon
were joined with asphalt. Joints of ships were sealed with asphalt. The Bible story of
Noah's ark claims that Noah used pitch, another name for asphalt, to waterproof the joints
in the ark. Asphalt was even used in Egypt to embalm mummies.
The advent of the automobile required hard road surfaces. After 1918, when the number of
cars and trucks began to increase rapidly, asphalt was taken from asphalt pits and used
for road surfaces. However, most of the asphalt used today is made from crude oil.
Surfaces of 90% of all paved roads in
the U.S. are asphalt because asphalt is economical and durable, can be constructed and
repaired quickly, and provides riding comfort. Asphalt cement for roads is a mixture of
asphalt and crushed stone, gravel, or sand. Asphalt is also used in varnishes, lacquers,
and inks, waterproofing and insulation materials, floor tiles and it is used to line
storage ponds, dams, and irrigation canals.
Source: The National Energy Foundation, from the Out of The Rock
program. Iif you would like addtional educational information and materials, stop by
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