Latin origin ‘gwitu-men’.
Earliest recorded use of bitumen by Sumerians.( 3500 to 2000 BC)
Since then used as adhesives , water proofing agents.
Manufactured from fractional distillation of crude oil.
The use of bitumen in road construction dates back to the middle of the nineteenth century.
Bitumen is claimed over 80% of the 100 million tonnes of the annual bitumen consumption is
used for paving applications in the construction and maintenance of roads.
It is used cause relatively inexpensive and generally provide good durability in paving mixtures
In addition, bituminous pavements are generally characterized by their immediate serviceability,
good riding quality and absence of joints.
OCCURRENCE AND SOURCES
Bitumen can be obtained from various sources. It
occurs naturally, but for most purposes it is
petroleum on which the world relies for its supplies of
Naturally occurring deposits of bitumen are formed
from the remains of ancient, microscopic algae and
other living things.
Under the heat (above 50°C) and pressure of burial
deep in the earth, the remains were transformed into
materials such as asphalt/bitumen, kerogen, or
It varies widely according to the source of the crude oil from which the bitumen originates.
Mainly composed of a large amount of hydrocarbons with minor amounts of structurally analogous
Some functional groups (heteroatoms) containing sulphur, nitrogen and oxygen atoms and trace
quantities of metals such as vanadium, nickel, iron, magnesium and calcium, which occur in the form
of inorganic salts and oxides or in porphyries structures.
Carbon 82% - 88%
Hydrogen 8% - 11%
Sulphur 0% - 6%
Oxygen 0% - 1.5%
Nitrogen 0% - 1%
PROPERTIES OF BITUMEN
Hardness : Penetration greater than 40 are used for road construction.
Softening point : property which make us to know whether given bitumen can be used at the
particular place i.e. softening point value should be higher than pavement temperature.
Ductility : Formation of the film and coating would be proper.
Viscosity : At low or high viscosity of bitumen coating of binder around aggregates will not be
Flash and Fire point : Flash point 175 degrees and,fire point usually 15 degree higher than flash
Durability : excessive rates of hardening (poor durability) can lead to premature binder
embrittlement and surfacing failure resulting in cracking and chip loss.
Specific gravity : lies between 0.97 to 1.02.
Complex process based on chemical composition pavement structure and climate.
Bitumen must be resistant to change in properties over time
Based on hardening or stiffening of asphalt material
1. short-term ageing.
2. long-term ageing.
Aging produces polar species that can form structures.
The main mechanisms of aging of bitumen are oxidation and loss of volatiles.
FACTORS AFFECTING AGING
Loss of oily components of bitumen by
volatility or absorption by porous aggregates.
Change in chemical composition of bitumen
molecules from reaction with atmospheric
Molecular structuring that produces
thixotropic effects (steric hardening).
OXIDATION AND LOSS OF
Occurs due to loss of lower molecular weight volatiles.
This loss rate depends on the concentrations, temperature, and environment.
As bitumen age they incorporate oxygen at reactive sites.
2. benzyclic carbonic groups
Hetero atoms in unaged bitumen may be polar or nonpolar.
Oxidation may be catalysed by components in the bitumen and by some metal compounds in the
The level of carbonyl or sulphoxide groups is not affected.
This mechanism is free radical and is initiated by peroxide formation.
The predominant materials formed in oxidation are oxygen polar functionalities.
EFFECT OF DIFFERENT TYPES
OF AGING ON BITUMEN
EFFECT OF THERMAL AND ULTRAVIOLET AGING
Because of the differences in air composition and the length of the solar radiation path
between plateaus and low-altitude plains, plateaus have unique climatic and environmental
features due to their more intense radiation, longer daylight hours, and especially their much
higher UV percentage, which ranges from 20% to 25% of the total solar light.
This is five times more than that on plains. Such intense UV radiation causes serious aging of
bitumen, which influences its performance. As a result, the durability of the pavement
decreases. Therefore it is important to study specifically the influence of UV radiation on
Three types of base bitumen from different sources with the same penetration grade are taken
as A ,B ,C.
COMPARISON OF THE PHYSICAL
PROPERTIES OF AGED BITUMEN.
After UV and Thermal aging penetration and ductility value decreased while softening point is
DEGRADATION RATES OF PHYSICAL INDICES OF AGED BITUMEN.
Figure shows the changes to physical indices of bitumen A and B caused by aging.
A is more UV radiation sensitive. Its penetration decreased by 42%.ductlity decreased by 77.6%
and the softening points increased by 22.6%,showing poor anti –UV ability.
B is not very sensitive to UV but is more thermally sensitive .as only small changes caused by
UV radiation but greater changes in ductility and softening points caused by thermal aging can
be seen .
Variations in the physical indices indicate than bitumen has different sensitivities due to
Thermal and UV aging.
TESTS ON AGING OF BITUMEN
Thin film oven test
Rolling thin film oven test
Pressure aging vessel
Thin film oven test (TFOT)
The TFOT was firstly introduced by Lewis and
A 50 ml sample of bitumen is stored at 163oC
for five hours in a layer of 3.2 mm thick.
Adopted by AASHTO in 1959 and by ASTM in
1969 (ASTM D1754, 1995a) as a means of
evaluating the hardening of bitumen.
The bitumen is not agitated or rotated during
the test, there is a concern that ageing
(primarily volatile loss) may be limited to the
‘skin’ of the bitumen sample.
Rolling thin film oven test (RTFOT)
Developed by the State of California
Department of Public Works, Division of
Highways, in 1963.
Eight glass containers each containing 35 g of
bitumen are fixed in a vertically rotating shelf,
hot air is blown into each sample bottle.
The bitumen flows continuously around the
inner surface of each container in a relatively
thin film at a temperature of 163oC for a
period of 75 minutes.
The vertical circular shelf rotates at a rate of
15rpm and the air flow is set at a rate of 4000
Pressure aging vessel (PAV)
The SHRP-A-002A research team developed a method
using the PAV to simulate the long-term.
The method involves hardening of bitumen in the
RTFOT or TFOT followed by oxidation of the residue in a
pressurised ageing vessel.
The PAV procedure entails ageing 50 g of bitumen in a
140 mm diameter within the heated vessel, pressurised
with air to 2070 kPa for 20h at temperatures between 90
It was found that 5 hours of PAV ageing at 100oC and
2070 kPa was equivalent to standard RTFOT ageing, and
that 25 hours of PAV ageing at 100oC and 2070 kPa was
equivalent to standard RTFOT+PAV ageing.
Rejuvenation in principle is simple ,replace the oils lost and
rebalance the bitumen composition so it is no longer brittle .
It would require sophisticated extraction testing and remodelling of
binder in the road.
The controlling factor in rejuvenation is diffusion, to ensure a
positive result, the level of diffusion must be controlled by careful
choice of rejuvenator and the delivery method .
Rejuvenation needs to be contact with the aged binder , ability to penetrate this
Emulsifier choice is needed. Emulsion must coat and wet adhere to stone
It must provide a Rejuvenation sealer, an enrichment emulsion or a chip sealing
Bitumen emulsion is a liquid product in which a substantial amount of bitumen
is suspended in a finely divided condition .in an aqueous medium and stabilized
by means of one or more suitable materials.
EFFECT OF FILLER
Filler is a fine material which passes a 0.63 mm sieve, derived from aggregate or
other granular material.
The greater the amount of filler added the less the bitumen ages.
Increasing the content indicates a smaller decrease in penetration a smaller
increase in the softening point and smaller increase in the bitumen indicator
that ,aging is less.
The addition of filler to the mixture can improve adhesion and cohesion.
The effects of addition of filler are directly related to the characteristics and
degree of concentration of filler in the bitumen filler system.
ADVANTAGES OF BITUMEN OVER
CONCRETE IN ROAD
Cost: Asphalt is usually about 30 to 40 percent cheaper than concrete.
Speed of Construction: To lay a new asphalt driveway it usually takes 1 - 2 days depending on
the size and scope of work. Where concrete can take up to several days longer to complete.
Cracking: All asphalt or concrete pavements can get lineal cracks this does not mean the
pavements are failing. The most common reason for this is expansive soil (clay). Asphalt is a
flexible pavement which means it is less likely to crack than concrete. That is why concrete has
control joints in it (scored lines/saw cut lines) to deal with any cracking.
Repairs and Maintenance: Generally asphalt is cheaper to repair than concrete due to the cost
of the material.
Asphalt is 100% recyclable.
Tom Wieringa and John Tailby,(2005), Rejuvenation Treatments for Aged
Aging of bitumen Tan yi-qiu, Wang Jia-Ni1, Feng Zhong-Liang2 and Zhou Xing ,
(2005). Influence and mechanism of ultraviolet aging on bitumen performance.
Wu, Jiantao (Jed) thesis 15-6-09 - University of Nottingham.
The Shell Bitumen Handbook ,By John Read, David Whiteoak.