Asphalt……..

Introduction

Asphalt 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.
It is a substance classed as a pitch.
Until the 20^th century, the term asphaltum was also used.
The term asphalt and bitumen are often used interchangeably to mean both natural and manufactured dorms of the substance.
This article uses “asphalt/bitumen” where either term is acceptable.
The terms asphalt and bitumen are often used interchangeably to mean both natural and manufactured forms of the substance.
In American English, Asphalt is the carefully refined residue from the distillation process of selected crude oils.
Outside the United States, the product is often called bitumen.
Geological terminology often prefers the term bitumen.
Another term, mostly archaic, refers to asphalt/bitumen as “pitch”.
The pitch used in this mixture is sometimes is sometimes found in natural deposits but usually made by the distillation of crude oil.

Terms

The viscosity of a fluid is a measure of its resistance to gradual deformation by shear stress or tensile stress.
For liquids, it corresponds to the informal notion of “thickness”. For example, honeyhas a higher viscosity than water.
Viscosity is due to friction between neighboring parcels of the fluid that are moving at different velocities.
Petroleum is a naturally occurring flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid compounds, that are found in geologic formations beneath the Earth’s surface.
Pitch is a name for any of a number of viscoelastic, solid polymers.
Pitch can be made from petroleum products or plants.
Petroleum-derived pitch is also called bitumen or asphalt.
Pitch produced from plants is also known as resin.

The viscoelastic property

Tar pitch is a viscoelastic polymer.
This means that even though it seems to be solid at room temperature and can be shattered with a hard impact, it is actually fluid and will flow over time, but extremely slowly.
The word asphalt is derived from the late Middle English, in turn from French asphalt, based on late Latin asphalton, asphaltum, which is the latinisation of the Greek, a word meaning “asphalt/bitumen/pitch.

Etymology

In British English, the word ‘asphalt’ is used to refer to a mixture of mineral aggregate and asphalt/bitumen.
The earlier work ‘asphaltum’ is now archaic and not commonly used.
In American English, ‘asphalt’ is equivalent to the British ‘bitumen’. However, ‘asphalt’ is laso commonly used as a shortened form of ‘asphalt concrete’ (therefore equivalent to the ?British ‘asphalt’ or ‘tarmac’).

Geological Information

Naturally occurring deposits of asphalt/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 degree c) and pressure of burial deep in the earth, the remains were transformed into materials such as asphalt/bitumen, kerogen, or petroleum.
Deposits at the La Brea Tar Pits are an example.
There are structural similarities between asphalt/bitumen and the organic matter in carbonaceous meteorites.
However, detailed studies have shown these materials to be distinct.

Modern Use

The largest use of asphalt/bitumen is for making asphalt concrete for road surfaces and accounts for approximately 85% of the asphalt consumed in the United States.
Asphalt concrete pavement material is commonly composed of 5% asphalt/bitumen cement and 95
% aggregates (stone, sand, and gravel).
Due to its highly viscous nature, asphalt/bitumen cement must be heated so it can be mixed with the aggregates at the asphalt mixing plant.
Asphalt concrete paving is widely used in airports around the world.

Is a type asphalt which differs from dense graded asphalt in that it has a higher asphalt/bitumen content, usually around 7-10% of the whole aggregate mix, as opposed to rolled asphalt concrete, which has only around 5% added asphalt/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 degree C (410 degree F) and is spread in layers to form an impervious barrier about 20 millimeters (0..8 in) thick.

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 pavement similar to hot-mixed asphalt, several inches in depth and asphalt emulsion are also blended into recycled hot-mix asphalt to create low-cost pavements.
Asphalt/bitumen is used to make Japan black, a lacquer known especially for its use on iron and steel.
Asphalt/bitumen is also used to seal some alkaline batteries during the manufacturing process.

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