Bitumen- Roadways Binder, Origin, Manufacturing, Types of Bitumen
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| Bitumen |
Bitumen
Bitumen is hydrocarbon
material of either natural or pyrogenous origin found in gaseous, liquid,
semi-solid or solid form and is completely soluble in carbon di-sulphide,
carbon tetra-chloride”. Bituminous binders used in pavement construction works
include both bitumen and tar. Both bitumen and tar have similar appearance,
black in color though they have different characteristics
material of either natural or pyrogenous origin found in gaseous, liquid,
semi-solid or solid form and is completely soluble in carbon di-sulphide,
carbon tetra-chloride”. Bituminous binders used in pavement construction works
include both bitumen and tar. Both bitumen and tar have similar appearance,
black in color though they have different characteristics
Bituminous materials or asphalts are much used for
roadway construction, at first because of their excellent binding
characteristics, water proofing properties and relatively low cost than other
binding material. Bituminous materials consists of bitumen which is a black or
dark in colour solid or viscous cementitious substances consists chiefly high
molecular weight hydrocarbons derived from distillation of petroleum or natural
asphalt, has adhesive properties, and is soluble in carbon disulphide. Tars are
residues from the destructive distillation of organic substances such as coal,
wood, or petroleum and are temperature sensitive than bitumen. Bitumen will be
dissolved in petroleum oils where unlike tar.
roadway construction, at first because of their excellent binding
characteristics, water proofing properties and relatively low cost than other
binding material. Bituminous materials consists of bitumen which is a black or
dark in colour solid or viscous cementitious substances consists chiefly high
molecular weight hydrocarbons derived from distillation of petroleum or natural
asphalt, has adhesive properties, and is soluble in carbon disulphide. Tars are
residues from the destructive distillation of organic substances such as coal,
wood, or petroleum and are temperature sensitive than bitumen. Bitumen will be
dissolved in petroleum oils where unlike tar.
Origin of Bitumen
Naturally
occurring deposits of bitumen are formed from the remains of ancient,
microscopic algae and other once-living things. When these organisms died,
their remains were deposited in the mud on the bottom of the ocean or lake
where they lived. Under the heat and pressure of burial deep in the earth, the
remains were transformed into materials such as bitumen, kerogen, or petroleum.
Deposits at the La Brea Tar Pitsare an example. There are structural
similarities between bitumens and the organic matter in carbonaceous
meteorites. However, detailed studies have shown these materials to be
distinct.
occurring deposits of bitumen are formed from the remains of ancient,
microscopic algae and other once-living things. When these organisms died,
their remains were deposited in the mud on the bottom of the ocean or lake
where they lived. Under the heat and pressure of burial deep in the earth, the
remains were transformed into materials such as bitumen, kerogen, or petroleum.
Deposits at the La Brea Tar Pitsare an example. There are structural
similarities between bitumens and the organic matter in carbonaceous
meteorites. However, detailed studies have shown these materials to be
distinct.
Manufacturing of Bitumen
When the crude petroleum is
refined bitumen is the residue or by product of petroleum. At a wide variety of
refinery processes, such as the straight distillation process, solvent
extraction process etc. may be used to produce bitumen of different consistency
and other desirable properties. Depending on the sources and characteristics of
the crude oils.
refined bitumen is the residue or by product of petroleum. At a wide variety of
refinery processes, such as the straight distillation process, solvent
extraction process etc. may be used to produce bitumen of different consistency
and other desirable properties. Depending on the sources and characteristics of
the crude oils.
Different types of
bitumen
bitumen
1. Cutback Bitumen
2. Bitumen Emulsion
3. Bituminous Primer
4. Modified Bitumen
1.
Cutback bitumen
Cutback bitumen
Normal practice is to heat
bitumen to reduce its viscosity. In some situations preference is given to use
liquid binders such as cutback bitumen. In cutback bitumen suitable solvent is
used to lower the viscosity of the bitumen. From the environmental point of
view also cutback bitumen is preferred. The solvent from the bituminous
material will evaporate and the bitumen will bind the aggregate. Cutback
bitumen is used for cold weather bituminous road construction and maintenance.
The distillates used for preparation of cutback bitumen are naphtha, kerosene,
diesel oil, and furnace oil. There are different types of cutback bitumen like
rapid curing (RC), medium curing (MC), and slow curing (SC). RC is recommended
for surface dressing and patchwork. MC is recommended for premix with less
quantity of fine aggregates. SC is used for premix with appreciable quantity of
fine aggregates.
bitumen to reduce its viscosity. In some situations preference is given to use
liquid binders such as cutback bitumen. In cutback bitumen suitable solvent is
used to lower the viscosity of the bitumen. From the environmental point of
view also cutback bitumen is preferred. The solvent from the bituminous
material will evaporate and the bitumen will bind the aggregate. Cutback
bitumen is used for cold weather bituminous road construction and maintenance.
The distillates used for preparation of cutback bitumen are naphtha, kerosene,
diesel oil, and furnace oil. There are different types of cutback bitumen like
rapid curing (RC), medium curing (MC), and slow curing (SC). RC is recommended
for surface dressing and patchwork. MC is recommended for premix with less
quantity of fine aggregates. SC is used for premix with appreciable quantity of
fine aggregates.
2.
Bitumen Emulsion
Bitumen Emulsion
Bitumen emulsion is a liquid
product in which bitumen is suspended in a finely divided condition in an
aqueous medium and stabilised by suitable material. Normally cationic type
emulsions are used in India. The bitumen content in the emulsion is around 60%
and the remaining is water. When the emulsion is applied on the road it breaks
down resulting in release of water and the mix starts to set. The time of
setting depends upon the grade of bitumen. The viscosity of bituminous
emulsions can be measured as per IS: 8887-1995. Three types of bituminous
emulsions are available, which are Rapid setting (RS), Medium setting (MS), and
Slow setting (SC). Bitumen emulsions are ideal binders for hill road
construction. Where heating of bitumen or aggregates are difficult. Rapid
setting emulsions are used for surface dressing work. Medium setting emulsions
are preferred for premix jobs and patch repairs work. Slow setting emulsions
are preferred in rainy season.
product in which bitumen is suspended in a finely divided condition in an
aqueous medium and stabilised by suitable material. Normally cationic type
emulsions are used in India. The bitumen content in the emulsion is around 60%
and the remaining is water. When the emulsion is applied on the road it breaks
down resulting in release of water and the mix starts to set. The time of
setting depends upon the grade of bitumen. The viscosity of bituminous
emulsions can be measured as per IS: 8887-1995. Three types of bituminous
emulsions are available, which are Rapid setting (RS), Medium setting (MS), and
Slow setting (SC). Bitumen emulsions are ideal binders for hill road
construction. Where heating of bitumen or aggregates are difficult. Rapid
setting emulsions are used for surface dressing work. Medium setting emulsions
are preferred for premix jobs and patch repairs work. Slow setting emulsions
are preferred in rainy season.
3.
Bituminous primers
Bituminous primers
In bituminous primer the
distillate is absorbed by the road surface on which it is spread. The
absorption therefore depends on the porosity of the surface. Bitumen primers
are useful on the stabilised surfaces and water bound macadam base courses.
Bituminous primers are generally prepared on road sites by mixing penetration
bitumen with petroleum distillate.
distillate is absorbed by the road surface on which it is spread. The
absorption therefore depends on the porosity of the surface. Bitumen primers
are useful on the stabilised surfaces and water bound macadam base courses.
Bituminous primers are generally prepared on road sites by mixing penetration
bitumen with petroleum distillate.
4.
Modified Bitumen
Modified Bitumen
Certain additives or blend
of additives called as bitumen modifiers can improve properties of Bitumen and
bituminous mixes. Bitumen treated with these modifiers is known as modified
bitumen. Polymer modified bitumen (PMB)/ crumb rubber modified bitumen (CRMB)
should be used only in wearing course depending upon the requirements of
extreme climatic variations. The detailed specifications for modified bitumen
have been issued by IRC: SP: 53-1999. It must be noted that the performance of
PMB and CRMB is dependent on strict control on temperature during construction.
The advantages of using modified bitumen are as follows
of additives called as bitumen modifiers can improve properties of Bitumen and
bituminous mixes. Bitumen treated with these modifiers is known as modified
bitumen. Polymer modified bitumen (PMB)/ crumb rubber modified bitumen (CRMB)
should be used only in wearing course depending upon the requirements of
extreme climatic variations. The detailed specifications for modified bitumen
have been issued by IRC: SP: 53-1999. It must be noted that the performance of
PMB and CRMB is dependent on strict control on temperature during construction.
The advantages of using modified bitumen are as follows
- Lower susceptibility to daily
and seasonal temperature variations - Higher resistance to
deformation at high pavement temperature - Better age resistance
properties - Higher fatigue life for mixes
- Better adhesion between
aggregates and binder - Prevention of cracking and
reflective cracking