TYPES based on the requirement of the industry.

TYPES
OF BITUMEN

  Bitumen can be found in different properties,
specification and the uses are based on the requirement of the industry. Bitumen
is available in variety of grade types which are penetration grade bitumen, oxidised
bitumen, cut-back bitumen, bitumen emulsion and polymer modified bitumen.

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  Penetration grade bitumen is bitumen that is
refined and manufactured at different viscosities. Penetration test need to be
carried out to characterise its hardness. Thus, it was named by penetration
bitumen. The range of penetration grade bitumen for road bitumen is from 15 to
450. But the range that commonly used is 25 to 200. By fluxing the remaining bitumen
with oils under partial control could bring the needed hardness of the bitumen.
The BS EN 1426 and BS EN 1427 distribute the penetration and softening point
values for the respective grades. This will be a big help in pinpointing the
equiviscosity of the bitumen grade and its hardness. Penetration values denote
the grades, for instance, 40/60 as a penetration value of 50 ± 10. The BS EN
13303 also contributes to the measure of loss on heating with respective limits
for all penetration bitumen grades. This is to certify that there are no
volatile components present. So, the setting and hardening of the bitumen
during the preparation is undergone do not get disturb. The BS EN 12592
provides the solubility values to make sure there is less or no contaminant in
the bitumen material. Penetration grade bitumen advantages are this bitumen may
provide a better interrelationship with a low temperature asphalt binder
properties than the viscosity test, which is performed at 60°C. Besides, the
test is quick and inexpensive, thus it can be used in the field. In contrast,
there are also its disadvantages. This bitumen’s shear rate is variable and
high during the test. Since asphalt binders typically behave as non-Newtonian
fluid at 25° C, this will affect the test results. The test also does not
provide information with which to establish mixing and compaction temperatures.

  Cut-back bitumen is bitumen that was blended
with more or less volatile hydrocarbon component. The viscosity of this bitumen has been minimised by
the addition of solvent which is normally obtained from petroleum. After the
application is done, the bitumen’s original viscosity is reclaimed. The solvent
that had been used in cutback bitumen is called the “cutter” or
“flux”. There are three types of solvents that have been used for the
blending process which are slow-curing, medium-curing or rapid-curing solvents.
The rate for bitumen to cure when get uncover to air can be determined by the
choice of the solvents. A rapid-curing (RC) solvent evaporated much faster than
a medium-curing (MC) solvent. The setting time of bitumen is influenced by the
evaporation rate of the solvent. The proportion of solvent added determines the
viscosity of the cutback bitumen at which the higher the proportion of solvent,
the lower the viscosity of the cutback. Cutbacks are more workable than
penetration grade bitumen at which they are more easily reshaped. Only slight
amount of heat are required to liquefy cutback bitumen than penetration bitumen,
thus make it much facile to be used at lower temperatures. Cutback bitumen can
be applied at lower temperatures compared to penetration grades due to its
lower bitumen solvents viscosity. However, cutback bitumen does have its own
weakness which it consumes non-renewable energy resources which are
fundamentally lost through evaporation.

 

  Oxidised Bitumen is the refined bitumen that
through further treatment by the introduction of processed air. This process
gives us oxidised bitumen. Soft bitumen is being instigated by the air that is
under pressure into it by maintaining the controlled temperature. Reaction of
this introduced oxygen and bitumen component forming the compounds of higher
molecular weight. Thus, rise in asphaltenes and maltenes content causing a
harder mix. This is lessening the ductility and temperature vulnerability of
the mix. Normally, oxidised bitumen is applied in industrial practices. Both
softening point and penetration test become the references in designing and
specifying this bitumen. For instance, oxidised bitumen 85/40 has softening
point of 85 ± 5°C and penetration point of 40 ± 5 dmm. Oxidised bitumen also
has to follow the solubility, loss on heating and streak point criteria. Oxidised
bitumen is utterly water resistant, highly flexible and durable. Furthermore,
it is chemically really stable. It is a very adaptable compound that is not
only chemically stable but also very durable compound apart from being
completely water resistant. It also has some conspicuous practical advantages
that make it very sought after compound in various applications. However, this
modified bitumen has one disadvantage to use in coating composition, which has
tendency to provide solutions that tend to extend the body on aging. These
undesirable body characteristics more pronounced in some solvents than in
others. It is significantly unhealthy among the case of the additional volatile
crude solvents. The initial high body of modify bitumen solutions is of course
undesirable, visible of the subsequent low solid content of solutions having
viscosities sufficiently low for application by the while a substitute for
slightly of the latter, with none substantial increase in body of the answer.

 

Bitumen
emulsion is the products in which droplets of bitumen preparation are scattered
in an aqueous medium. An emulsifier is applied to stabilise the mixture.
Bitumen emulsion lets the handling, transport and application of bitumen at
lower temperatures and is mainly implemented in road surfacing applications. This
type of bitumen forms a two-phase system consisting of two immiscible liquids,
bitumen and water, stabilised by an emulsifier. One of them is dispersed as
fine globules within the other liquid. Bitumen emulsion is formed when discrete
globules of bitumen dispersed in a continual form of water. It is essential for
laying purposes. Basically, emulsions with low bitumen content and low
viscosity are prone to settlement. This settlement can be minimised by balancing
the densities of two phases. To achieve this, addition of calcium chloride to
the aqueous phase is a main way. However, the coefficient of thermal expansion
of bitumen and aqueous phase are not the same. Only at a specific temperature
can make their densities to be the same. The phase behaviour’s viscosity can be
increased by introducing a yield value, thus settlement can be eliminated. There
are many advantages of bitumen emulsion, one of them are bitumen emulsion
provides a convenient and environmentally friendly option as it is water based.
Besides, it doesn’t need extra heat while placing. It is also used in
bituminous road construction, maintenance and repair work. However, bitumen
emulsions do have its flaw. The setting time may vary due to temperature, wind
and type of emulsion. In addition, not all single type of bitumen emulsion can
be applied for all works. It relies on the aggregate type setting time.

 Polymer modified bitumen is the type of
bitumen achieved by the modification of strength and the rheological properties
of the penetration graded bitumen. The polymer used can be either plastic or
rubber. These polymers differs the strength and the viscoelastic properties of
the bitumen. This is achieved by elastic response increase, improvement in
cohesive property, enhancement in fracture strength and providing ductility.
Some of the examples of rubber polymers used are styrene block copolymers,
synthetic rubbers, natural and recycled rubbers. Plastics which are
thermoplastic polymers are also used. Polymer modified bitumen also one of the
specially designed and engineered bitumen grades that is used in making
pavement, roads for heavy duty traffic and home roofing solutions to withstand
extreme weather conditions. It is normal bitumen with added polymer which gives
its extra strength, high cohesiveness and resistance to fatigue, stripping and
deformations, making it a favourable material for infrastructure. When polymer
is added to regular bitumen, it becomes more elastomeric, which provides it
with additional elasticity. The polymer that is added is styrene butadiene
styrene (SBS) which acts as a binder modification agent. The primary objective
of SBS polymer modified bitumen is to provide extra life to pavement, roads and
construction designs. Some of the qualities exhibited by polymer modified
bitumen are higher rigidity, increase resistance to deformations, increase
resistance to cracks and stripping, better water resistance properties and high
durability. Some popular plastomers and thermoplastic elastomers in bitumen
modification are discussed regarding their advantages and disadvantages.
Although polymers improve bitumen properties to some extent, there are still
some drawbacks limiting the future development of bitumen polymer modification
such as high cost, low ageing resistance and poor storage stability of polymer
modified bitumen.

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