23
History and Terminology
1.5.3 AsPHAlt
Asphalt (Chapter 26) is manufactured from petroleum and is a black or brown material that has a
consistency varying from a viscous liquid to a glassy solid. To a point, asphalt can resemble bitumen, hence the tendency to refer to bitumen (incorrectly) as native asphalt. It is recommended that
there be differentiation between asphalt (manufactured) and bitumen (naturally occurring) other
than by use of the qualifying terms petroleum and native since the origins of the materials may be
reflected in the resulting physicochemical properties of the two types of materials. It is also necessary to distinguish between the asphalt that originates from petroleum by refining and the product
in which the source of the asphalt is a material other than petroleum, for example, wurtzilite asphalt
(Bland and Davidson, 1967). In the absence of a qualifying word, it is assumed that the term asphalt
refers to the product manufactured from petroleum.
When the asphalt is produced simply by distillation of an asphaltic crude oil, the product can be
referred to as residual asphalt or straight run asphalt. If the asphalt is prepared by solvent extraction
of residua or by light hydrocarbon (propane) precipitation, or if blown or otherwise treated, the term
should be modified accordingly to qualify the product (e.g., propane asphalt and blown asphalt).
Asphalt softens when heated and is elastic under certain conditions. The mechanical properties of
asphalt are of particular significance when it is used as a binder or adhesive. The principal application
of asphalt is in road surfacing, which may be done in a variety of ways. Light oil dust layer treatments
may be built up by repetition to form a hard surface, or a granular aggregate may be added to an
asphalt coat, or earth materials from the road surface itself may be mixed with the asphalt.
Other important applications of asphalt include canal and reservoir linings, dam facings, and
sea works. The asphalt so used may be a thin, sprayed membrane, covered with earth for protection
against weathering and mechanical damage, or thicker surfaces, often including riprap (crushed
rock). Asphalt is also used for roofs, coatings, floor tiles, soundproofing, waterproofing, and other
building–construction elements and in a number of industrial products, such as batteries. For certain applications, an asphaltic emulsion is prepared, in which fine globules of asphalt are suspended
in water.
1.5.4 tAr And PItCH
Tar is a product of the destructive distillation of many bituminous or other organic materials and is
a brown to black, oily, viscous liquid to semisolid material.
Tar is most commonly produced from bituminous coal and is generally understood to refer to the
product from coal, although it is advisable to specify coal tar if there is the possibility of ambiguity.
The most important factor in determining the yield and character of the coal tar is the carbonizing
temperature. Three general temperature ranges are recognized, and the products have acquired
the following designations: low-temperature tar (approximately 450°C–700°C; 540°F–1290°F),
mid-temperature tar (approximately 700°C–900°C; 1290°F–1650°F), and high-temperature tar
(approximately 900°C–1200°C; 1650°F–2190°F). Tar released during the early stages of the decomposition of the organic material is called primary tar since it represents a product that has been
recovered without the secondary alteration that results from prolonged residence of the vapor in the
heated zone.
Treatment of the distillate (boiling up to 250°C, 480°F) of the tar with caustic soda causes separation of a fraction known as tar acids; acid treatment of the distillate produces a variety of organic
nitrogen compounds known as tar bases. The residue left following removal of the heavy oil, or
distillate, is pitch, a black, hard, and highly ductile material.
In the chemical process industries, pitch is the black or dark brown residue obtained by distilling
coal tar, wood tar, fats, fatty acids, or fatty oils.
Coal tar pitch is a soft to hard and brittle substance containing chiefly aromatic resinous compounds along with aromatic and other hydrocarbons and their derivatives; it is used chiefly as road
History and Terminology
1.5.3 AsPHAlt
Asphalt (Chapter 26) is manufactured from petroleum and is a black or brown material that has a
consistency varying from a viscous liquid to a glassy solid. To a point, asphalt can resemble bitumen, hence the tendency to refer to bitumen (incorrectly) as native asphalt. It is recommended that
there be differentiation between asphalt (manufactured) and bitumen (naturally occurring) other
than by use of the qualifying terms petroleum and native since the origins of the materials may be
reflected in the resulting physicochemical properties of the two types of materials. It is also necessary to distinguish between the asphalt that originates from petroleum by refining and the product
in which the source of the asphalt is a material other than petroleum, for example, wurtzilite asphalt
(Bland and Davidson, 1967). In the absence of a qualifying word, it is assumed that the term asphalt
refers to the product manufactured from petroleum.
When the asphalt is produced simply by distillation of an asphaltic crude oil, the product can be
referred to as residual asphalt or straight run asphalt. If the asphalt is prepared by solvent extraction
of residua or by light hydrocarbon (propane) precipitation, or if blown or otherwise treated, the term
should be modified accordingly to qualify the product (e.g., propane asphalt and blown asphalt).
Asphalt softens when heated and is elastic under certain conditions. The mechanical properties of
asphalt are of particular significance when it is used as a binder or adhesive. The principal application
of asphalt is in road surfacing, which may be done in a variety of ways. Light oil dust layer treatments
may be built up by repetition to form a hard surface, or a granular aggregate may be added to an
asphalt coat, or earth materials from the road surface itself may be mixed with the asphalt.
Other important applications of asphalt include canal and reservoir linings, dam facings, and
sea works. The asphalt so used may be a thin, sprayed membrane, covered with earth for protection
against weathering and mechanical damage, or thicker surfaces, often including riprap (crushed
rock). Asphalt is also used for roofs, coatings, floor tiles, soundproofing, waterproofing, and other
building–construction elements and in a number of industrial products, such as batteries. For certain applications, an asphaltic emulsion is prepared, in which fine globules of asphalt are suspended
in water.
1.5.4 tAr And PItCH
Tar is a product of the destructive distillation of many bituminous or other organic materials and is
a brown to black, oily, viscous liquid to semisolid material.
Tar is most commonly produced from bituminous coal and is generally understood to refer to the
product from coal, although it is advisable to specify coal tar if there is the possibility of ambiguity.
The most important factor in determining the yield and character of the coal tar is the carbonizing
temperature. Three general temperature ranges are recognized, and the products have acquired
the following designations: low-temperature tar (approximately 450°C–700°C; 540°F–1290°F),
mid-temperature tar (approximately 700°C–900°C; 1290°F–1650°F), and high-temperature tar
(approximately 900°C–1200°C; 1650°F–2190°F). Tar released during the early stages of the decomposition of the organic material is called primary tar since it represents a product that has been
recovered without the secondary alteration that results from prolonged residence of the vapor in the
heated zone.
Treatment of the distillate (boiling up to 250°C, 480°F) of the tar with caustic soda causes separation of a fraction known as tar acids; acid treatment of the distillate produces a variety of organic
nitrogen compounds known as tar bases. The residue left following removal of the heavy oil, or
distillate, is pitch, a black, hard, and highly ductile material.
In the chemical process industries, pitch is the black or dark brown residue obtained by distilling
coal tar, wood tar, fats, fatty acids, or fatty oils.
Coal tar pitch is a soft to hard and brittle substance containing chiefly aromatic resinous compounds along with aromatic and other hydrocarbons and their derivatives; it is used chiefly as road