Puma Bitumen - Bitumen Basics

Bitumen Basics Puma Bitumen
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Bitumen Basics
basics
The description of bitumen as ‘mankind's oldest engineering
material’ can be supported by a considerable amount of
evidence from scholars. Nearly 3000 years BC the Sumerians
in Mesopotamia used bitumen to fasten into the eye sockets
of statues the materials such as ivory or mother-of-pearl
pieces that represented the eyes. They also sculptured
votive offerings out of a mixture of bitumen and clay.
Some thousand years later, bitumen was being used by
the early Babylonians as a building material because of its
properties as an adhesive and water-proofing agent. With the
passing of centuries, it became the standard material used
in civil engineering and architectural projects to hold bricks
and stones together and line drains, watercourses and grain
silos. It was also used to create damp courses and seal the
flat roofs of the houses in the same way as it is used today.
Its importance in paving was also appreciated.
About 600 BC King Nebuchadnezzar of Babylon had the city
wall, intended to restrain the waters of the Euphrates, rebuilt
with burnt bricks and bitumen because the wall of dried clay
bricks had failed to keep the waters at bay. The Babylonians
developed a technique for building houses from layers of
bricks, bitumen and clay, reinforced with reeds. The system
was so successful that they were able to build towers up
to twelve storeys high. Nearly two thousand years later,
archeologists excavating the site of the ancient city found
traces of the bitumen that had been used for building.
Apart from its properties, the reason why bitumen was
widely used in this area was its availability in various forms.
It oozed out of the ground in certain places and was even
found floating in lumps on waterways that were so useful
for moving it to where it was wanted. It was also available as
a solid material in the form of bituminous limestone, which
was used as the basis for small carvings.
Given its general availability, it is not surprising that bitumen
has a part to play in many of the great legends of Biblical and
pre-Biblical times. It is said to have been used in the building
of the Tower of Babel and for the waterproofing of Noah's
Ark and Moses' wicker basket.
The Romans were enthusiastic about the medicinal qualities
of bitumen for preventing and curing a number of ailments
including boils, toothache and ringworm. It was also in favour
amongst Roman ladies as a means of beautifying their eyebrows.
As civilisation developed in Europe, it did so without
significant use of bitumen as it was not a widely available
material. Christopher Columbus and Sir Walter Raleigh found
the lakes of asphalt in Trinidad useful for re-caulking their
ships for the return voyage. Apart from maritime usage,
bitumen was used mainly for medicinal, cosmetic and crop
protection purposes.
The extent of knowledge about bitumen in these times was
quite variable. On the one hand, the German metallurgist
Georg Agricola was writing in the early part of the sixteenth
century that "Bitumen is produced from mineral waters
containing oil, also from liquid bitumen and from rocks
containing bitumen. Liquid bitumen sometimes floats in large
quantities on the surface of wells, brooks and rivers and is
collected with buckets or other pots. Small quantities are
collected by means of feathers, linen towels and the like.
The bitumen easily adheres to these objects and is collected
in big copper or iron vessels and the lighter fractions
evaporated by heating. The residual oil is used for different
purposes and some people mix it with pitch, others with
used axle oil to make it thicker."
On the other hand, the entry for bitumen in Blount's Glossary
published in 1656 defined it as "…a kind of clay or slime
naturally clammy, like pitch, growing in some countries of Asia."
By the middle of the nineteenth century, serious attention
was being given to the problem of the dust raised by the
horse-drawn traffic in towns. The availability of a regular
supply of coal tar from local coal-gas works led to its use
in treating streets and pavements. The realisation that the
horseless carriage was here to stay and would need streets
and roads constructed to a hitherto unimagined standard of
smoothness and durability resulted in serious attention being
given to the elements needed for their creation. Rock asphalt
and the Trinidad lake were the sources of bitumen first used
to bind mixtures of aggregates in road building in the modern
style. By the turn of the century the potential of petroleum
as a readily available source of low-cost, high quality bitumen
was being exploited on a small scale.
As bitumen production grew with the rise of the motorcar
and the universal demand for paved highways, so too did
the proportion of bitumen derived from petroleum refining
to the extent that today most bitumen is sourced from the
distillation of crude petroleum oil.
In the USA, bitumen is referred to as asphalt or asphalt
cement. In the term rock asphalt, it defines a mineral
substance that may be impregnated with bitumen or pitch.
Outside the USA, the word asphalt means a mixture of
bitumen and mineral aggregates laid as a road surface.
Introduction and Historical Perspective 03Index
Introduction and Historical Perspective
Bitumen Sources and Types
Applications
Manufacturing Process
Test Proceedures
Optimising Bitumen Performance
Glossary
Puma Bitumen
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Bitumen Basics
What is Bitumen?
Bitumen is a non-crystalline, black or dark brown viscous
material, which is substantially soluble in organic solvents,
such as toluene and carbon disulphide, and which possesses
adhesive and water-proofing qualities.
It consists essentially of hydrocarbons and typically comprises
at least 80% carbon and 15% hydrogen. The remainder is
oxygen, sulphur, nitrogen and traces of various metals.
Sources of Bitumen
Bitumen can be obtained from various sources. As mentioned
earlier, it occurs naturally, but for most purposes it is petroleum
on which the world relies for its supplies of bitumen. The
bitumen content of crude petroleum oil can vary between
15% and 80%, but the more normal range is 25% to 40%.
The three broad classifications for crude oils are:
• bitumen based
• paraffin based
• bitumen and paraffin based.
Depending on the type of crude petroleum oil, bitumen is
present either in the form of a colloidal dispersion, or in a
true solution. During the refining process, as petroleum oils
are taken away by distillation, the proportion of oil to bitumen
particles changes. Instead of these particles being dispersed
and relatively few in number, they become closer to one
another and their size increases. At the point when the
distillation process is usually stopped, the petroleum bitumen
is a colloidal dispersion of black solids (hydrocarbons). These
are known as asphaltenes, which are dispersed in an oily
brown-yellow liquid, known as the maltenes fraction. Also
present to act as a stabilising agent to keep the asphaltenes
in suspension are another group of hydrocarbons known as
resins.
Bitumen is found in nature in several forms, from the hard,
easily crumbled bitumen in rock asphalt to the softer, more
viscous material found in oil sands and so-called asphalt
lakes. It is commonly mixed with varying proportions of
mineral or vegetable impurities that need to be extracted
before it can be used effectively as an engineering material.
Bitumen may also be found as asphaltite, natural bitumen
without impurities that varies in the extent to which it is
soluble in carbon disulphide. Natural bitumen, like petroleum,
occurs as the result of the special decomposition of marine
debris. It will have been moved over many thousands of
years through porous rocks such as limestone or sandstone,
often by volcanic action. In some areas notable for their
petroleum resources, for example the Middle East, semi-fluid
bitumen can be found oozing out of fissures near hot springs
or seeping out of the ground.
Figure 1: The decomposition of marine debris over millions of
years produces natural bitumen in a petroleum residue, which is
extracted through the refining process.
Rock asphalt, with its variable and relatively low content of
bitumen, tends to be found away from the places where
bitumen is needed. It is costly to move around and to process.
It is important to draw the distinction between bitumen and
coal tar. Although coal tar is black and viscous like bitumen, it
is obtained from the carbonisation of coal and therefore has
very different chemical properties.
Engineering projects in every part of the world, from the
construction of transcontinental highways to the water-
proofing of flat roof surfaces, rely on the particular properties
of bitumen. Crude petroleum oil processed by the petroleum
industry provides all but a small percentage of this vital material.
04 Bitumen Sources and Types
basics
Properties
Bitumen is a strong and durable adhesive that binds together
a very wide variety of other materials without affecting their
properties. Its durability is essential to major engineering
projects such as roads and waterways where it must perform
for up to 20 years or more.
Bitumen is insoluble in water and can act as an effective
waterproofing sealant. It also resists action by most acids,
alkalis and salts and does not contaminate water, so it can be
used to line watercourses.
Bitumen is a thermoplastic material: it softens and becomes
liquid with the application of heat and hardens as it cools.
It can be spread relatively easily in the areas where it is
required because it can readily be liquefied by one of three
methods:
• applying heat
• dissolving it in petroleum solvents
• dispersing it in water (emulsification).
Bitumen gives controlled flexibility to mixtures of mineral
aggregates, which is why so much of the total annual
production is used in road building. It is available at an
economic cost virtually all over the world.
Types of Bitumen
There are six major classifications of petroleum bitumen
produced by the refining and manufacturing process:
Paving grade bitumen (or asphalt cement in the USA) is
the most widely used bitumen and is refined and blended
to meet road engineering and industrial specifications that
take into account different climatic conditions. Paving grade
bitumen may also be considered as the parent bitumen from
which the other forms are produced.
Cutback bitumens consist of bitumen that has been diluted
in solvent (cutter or flux) to make it more fluid for application.
The fluidity of cutback bitumens (or cutbacks as they are
known) depends on the degree of hardness of the bitumen
and the proportion of diluent. Cutbacks are classified
according to the time it takes for them to cure, or become
solid due to the evaporation of the diluent. Classifications are
rapid curing (RC), medium curing (MC) or slow curing (SC).
A cutback varies in behaviour according to the type of cutter
or flux used as the diluent with white spirit commonly used
for RC grades, kerosene for MC and diesel for SC.
Bitumen emulsions are dispersions of bitumen in water.
Hot bitumen, water and emulsifier are processed in a high-
speed colloid mill that disperses the bitumen in the water
in the form of small droplets. These droplets or particles
of bitumen are normally in the 5-10 micrometre size range
but may be even smaller. The emulsifier assists in forming
and maintaining the dispersion of fine droplets of bitumen.
Bitumen emulsions normally comprise between 30% and
80% bitumen by volume. If the bitumen starts to separate
from the water solution in storage, the emulsion can usually
be easily restored by gentle agitation to redisperse the droplets.
Bitumen emulsions have a low viscosity compared to
the bitumen from which they are produced and can be
workable at ambient temperatures. Their application requires
controlled breaking and setting. The emulsion must not
break before it is laid on the road surface but, once in place,
it should break quickly so that the road can be in service
again without delay.
Figure 2: Particles of bitumen dispersed in water to make
bitumen emulsions are usually between 5 and 10 micrometres
in size. This diagram gives an indication of relative size.
05
40 micrometres
Limit of visibility
to the naked eye
100 micrometres
Grain of salt
70 micrometres
Diameter of human hair
25 micrometres
White blood cells
8 micrometres
Red blood cells
2 micrometres
Bacteria

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Bitumen Basics
06
Fine
Coarse
The mechanical performance of
bitumen emulsions can be tailored like
that of other construction materials.
Bitumen emulsions are divided into
three categories:
• Anionic with negatively charged droplets
• Cationic with positively charged droplets
• Non-ionic with neutral droplets.
The main grades for bitumen emulsions
are classified as follows:
Anionic Cationic
ARS CRS Rapid setting
AMS CMS Medium setting
ASS CSS Slow setting
The development of bitumen emulsions is an area where
technological progress is still being made to meet current and
emerging engineering demands. The first emulsions were
the anionic types. They are currently less favoured than the
cationic types because the positively charged globules of
bitumen in cationic emulsions better coat the majority of
aggregate types and result in greater adhesion. Use of cationic
emulsions is therefore preferred in most applications.
Modified bitumens are formulated with additives to
improve their service performance by changing such
properties as their durability, resistance to ageing, elasticity
and/or plasticity. The most important modifiers are polymers.
Polymer modified binders (PMB) are a major advancement
in bituminous binder technology as these materials better
satisfy the demands of increasing traffic volumes and loads
on our road networks. As well as natural rubbers, polymers
such as styrene butadiene styrene (SBS), polybutadiene
(PBD) and ethylene vinyl acetate (EVA) are commonly used
to modify bitumen.
Multigrade bitumen is a chemically modified bitumen
that has the properties of a hard paving grade bitumen at
high service temperatures coupled with the properties of a
soft paving grade bitumen at low temperatures (i.e. it has
properties that span multiple grades). Multigrade bitumens
provide improved resistance to deformation and reduce the
detrimental effects of high service temperatures, whilst
providing reduced stiffness at low service temperatures than
exhibited by a similar normal paving grade bitumen.
Industrial bitumens (or oxidised bitumens) are made by
blowing air through hot paving grade bitumen. The so-called
blowing process results in harder bitumen that softens at a
higher temperature than that at which paving grade bitumen
softens. Industrial bitumens also have more rubber-like
properties and their viscosities are much less affected by
changes in temperature than is the case with paving grade
bitumen.
Bitumen Handling
The four major factors involved in handling bitumen are:
• the high handling temperatures and the need for purpose-
designed storage and transport tanks and equipment
• the flammable nature of certain grades, particularly
cutbacks
• the need to safeguard the health and safety of personnel
• the training of personnel.
Owing to their high viscosity, almost all bitumen and
bituminous products must be heated to make them sufficiently
fluid for bulk distribution and application. Contact with
bitumen or the equipment involved in transporting, storing or
applying it can cause severe skin burns at the recommended
handling temperatures. For example, even a fleeting touch at
80°C can be expected to burn unprotected skin.
It is essential that anyone working with bitumen or
bituminous products make themselves familiar with the
necessary health, safety and environmental considerations.
Users are advised to always refer to product Material
Safety Data Sheets (MSDS) for a full description of hazards
associated with the use of bitumen products.
Figure 3:
Microscopic
representation of
emulsion structures.
basics
Road Construction and
Maintenance
Over 80% of the 100 million tonnes of worldwide annual
bitumen consumption is used for paving applications in the
construction and maintenance of roads. The remainder is used
for various purposes. The use of bitumen in road maintenance
can be up to four times its use in road construction.
An understanding of how roads are built is necessary for an
appreciation of the importance of the role played by bitumen.
Modern road design and construction techniques are aimed
at building flexible road layers or courses so that the tensile
and compressive stresses imposed by passing traffic are
distributed evenly through these layers, according to their
relative strengths. This ensures that neither the ground
supporting the road nor the individual layers are permanently
deformed by these concentrated stresses.
The courses must also be made weather resistant and
durable. Bitumen plays a major part in meeting this
requirement because it strongly binds the aggregate particles
and seals and fills the voids between them. Its effectiveness
depends on the aggregate specification, the size and number
of voids and the type of bitumen. By sealing the gaps,
bitumen makes it difficult for water to penetrate the road
courses and damage the natural foundation of the road.
In the context of road building, the entire road structure is
called the pavement.
The lowest layer of a road is the natural soil of the subgrade.
For a new road the subgrade is carefully prepared by modern
machinery, but for an old road this layer consists of whatever
has been left by generations of traffic.
The rest of the road is made up of layers of aggregates and
bitumen, each designed to do a specific job (see Figure 4
on page 9). Aggregate is the term used to describe hard
non-metallic minerals such as crushed rock, gravel, sand and
slag. Aggregates must meet engineering specifications that
include shape, strength, surface characteristics and size.
The subbase is the first layer put down by the road builder
and consists of compacted granular material — stone, gravel
or sand. Its function is to contribute towards the strength of
the road and give the road building machinery an operating
platform.
The base course is a mixture of aggregates and bitumen
used as a structural layer. It adds to the strength of the road
and is an even surface foundation for the top layer.
The wearing course is the top layer normally consisting of a
more finely textured mixture of aggregates and bitumen. Its
role is to act as a smooth running surface for traffic. It must
also be as weather-proof as possible and resist the continual
action of the abrasive forces imposed by the vehicles as
they pass along it. The wearing course should also disperse
surface water effectively to minimise the danger of skidding.
Where appropriate, a tack coat of bitumen may be applied
between courses to ensure adhesion of the layers.
The layers of asphalt in a road pavement can vary widely in
maximum stone size used and thickness laid, from as low
as 15mm thickness using 5mm maximum stone size up to
250mm layers using up to 40mm maximum stone size.
Variable Design Factors
The exact make-up of a road will depend on several variable
factors such as the weight and volume of traffic it has been
designed to carry, local climatic conditions and the availability
of mineral aggregates. In most cases, bitumen will be needed
for its properties of waterproofing and durability and as the
cheapest adhesive generally available. A minor secondary
road may use bitumen only for its top two courses, at the
rate of 7 tonnes per kilometre. A highway engineer may
call for three asphalt courses, with tack coats in between,
because of asphalt's superior load bearing properties. In this
case, bitumen consumption can amount to 1,000 tonnes
per kilometre. The bitumen percentage in asphalt is usually
between 4-8%.
Table A: This table defines some typical road construction and
maintenance applications for different types of bitumen.
Applications 07
Cutback
manufacture
Examples of use C170 C320 C600 Low
viscosity
High
viscosity
Paving grades Cutback grades Emulsions Modified
bitumens
GENERAL ROAD CONSTRUCTION AND MAINTENANCE APPLICATIONS
Emulsion
manufacture
Hotmix
asphalt
Sprayed seals
Tack coat

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Bitumen Basics
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Hot Mix
The mixing of aggregates and bitumen to produce asphalt
may take place at a purpose-built plant located away from
the road construction site, or it may be done at the site itself.
Controlled amounts of various size aggregates, which have
been carefully blended and graded to meet the required
specification, are dried and heated before being mixed with
a measured quantity of hot bitumen. All this takes place
in a purpose-built plant. The hot mixture, or hot mix, at a
temperature of up to 160°C, is carried to the construction
site and laid while still hot.
The above describes, in simple terms, a process in which
skill and experience are combined with computerised control
systems to carry out a complex series of operations. Various
sizes of aggregate dry out, gain and retain heat at different
rates. Their temperature must be controlled so that the
bitumen does not cool when it is mixed with the aggregates.
The supply of aggregates is continuously weighed by scales
linked to the pump metering the bitumen to ensure that
a constant ratio of aggregate to bitumen is maintained.
The mixing time should be no longer than is necessary for
the uniform distribution of the bitumen as a coating for the
aggregate particles, otherwise the bitumen film will harden
due to oxidation as it is exposed to air. The durability of the
mixture will be impaired if the mixing process takes too
long. Continuous operation of the plant is required to provide
consistent high quality mixtures. This, in turn, means that
all parts of the operation must be integrated so there are no
hold-ups as the drying, screening, mixing, transporting and
laying processes are carried out.
Bitumen supplies are ordered daily to meet the production
schedules on the road gangs' programs for the following
day. As bitumen storage capacity is usually limited, delivery
has to be made on a 'when required' basis, often within
thirty minutes of the target time based on the moment when
the aggregates have been heated to the right temperature
for mixing with bitumen. Any delay means that expensive
fuel is wasted in keeping the aggregate at the right
temperature. This precision in delivery calls for a high degree
of commitment on the part of the supplier in terms of capital
equipment, logistics and technical expertise.
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Direction of load
Wearing course
Tack coat
Base course
Tack coat
Sub-base
Formation level
Subgrade
(natural soil)
Figure 4: Distribution of load through a bituminous road

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Bitumen Basics
10
s
Asphalt and Other Treatment Types
Asphalt mixtures have been classified into a number of
different types, which may be simply stated as:
Dense-graded Asphalt or Asphaltic Concrete: a dense,
continuously graded mixture of coarse and fine aggregates,
mineral filler and bitumen, having a carefully controlled air
void content.
Hot Rolled Asphalt: a sand-based material, bound with high
viscosity grade bitumen, and having approximately 30%
selected stone content, with larger stones rolled into the
surface.
Stone Mastic Asphalt: a high stone content mixture where
the large stones form a load-bearing matrix within the
mixture to provide high resistance to deformation with the
interstices substantially filled with bitumen/filler mastic.
Table B: Asphalt mixture compositions
Open-graded Asphalt: a mixture of graded aggregates and
bitumen produced to provide an open texture and high air
voids content to allow ready drainage of water through the
finished asphalt layer – also known as Porous Asphalt and
Drainage Asphalt.
Tack Coat: a thin layer of emulsified or cutback bitumen that
bonds a layer of road to the layer beneath. Current practice is
to favour the use of bitumen emulsions in place of cutbacks
in this application.
Sprayed Seal: also known as surface dressings and chip
seals, these involve spraying a coating of bitumen onto the
surface of a wearing course or granular pavement. Sprayed
seals can be sprayed as an emulsion, a cutback or as neat
paving grade bitumen. Either a single or double coating of
aggregates or stone chippings is applied. These treatments
are applied to renovate and waterproof old roads that require
maintenance or to protect unbound granular pavements in
new constructions. An example of a remedial treatment is a
fog seal, which is a coat of bitumen emulsion applied to an
existing surface to seal cracks or to replenish aged bitumen
as a maintenance treatment.
Bituminous Slurry Surfacing: an important maintenance
treatment for the surface in which a mixture of fine
aggregates, filler and emulsified bitumen is applied to a
structurally sound road surface for minor shape correction
and to improve skid resistance. It has the advantage that it
can be applied rapidly and at a relatively low cost by a truck-
mounted mixing plant.
Figures 5 and 6: This
purpose-built asphalt mixing
plant grades and dries the
aggregates and then mixes
them with bitumen. All
aspects of the mixing plant
are carefully controlled from
the computer console.
(Pictures courtesy of Boral
Asphalt).
COMPOSITION OF ROAD SURFACE
Dense-graded
Asphalt
Hot Rolled
Asphalt
Stone Mastic
Asphalt
Open-graded
Asphalt
Bitumen
content %
4-7%
3-5%
6-9%
3-5%
6-8% 5-7%
2-4% 18-20%
Air voids
content %
basics
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Road Recycling
The techniques of road recycling reclaim the materials used
to build roads. They offer benefits in terms of reduced
demands for aggregates and energy. The layers of road
surface are ripped up, crushed and reprocessed with varying
proportions of fresh aggregate, new bitumen or bitumen
emulsion and, if necessary, a recycling agent. The process
may be carried out on site (in situ), or the reclaimed material
can be transported to and from the site to be mixed in a
dedicated static plant. Such reclaimed material is known as
RAP or reclaimed asphalt pavement.
Industrial Usage
The use of bitumen in industrial applications accounts
for less than 20% of world bitumen consumption. It
is nevertheless important to those manufacturers and
engineers who rely on its particular properties as an
economical binder and protector. In many parts of the world
it is used extensively to waterproof the roofs of houses,
often in the form of shingles, which are strips of felt first
impregnated with bitumen and then covered on both sides
with harder bitumen and a coating of mineral granules. A
similar construction technique involves sheets of bitumen-
saturated felt laid onto a flat roof with layers of bitumen
below, between and above them. By contrast, bitumen is
also used in damp-proofing and floor tiles.
Other materials, particularly felts and papers, are
impregnated with bitumen to improve their performance as
insulators. Packaging papers, printing inks, linoleum, sound
deadening felts hidden inside car bodies and undersealing
compounds beneath them, electrical insulating compounds
and battery boxes are some of the hundreds of industrial and
domestic products likely to contain industrial grade bitumen.

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Bitumen Basics
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Refinery Processes
In an oil refinery, the crude oil being processed is separated
into different ‘cuts’ on the basis of their boiling range. In
atmospheric distillation, which is the first stage of this
continuous process, the crude oil is heated to 300°C-350°C
and the more volatile components, e.g. petrol and kerosene,
are distilled off. This leaves a residue called atmospheric
residue, which is then further distilled under vacuum.
The actual processing temperature of the residue is 350°C-
390°C, but because of the applied vacuum, the further
effective distillation cut point is 500°C-560°C. This vacuum
distillation process yields further volatile products known as
vacuum distillates and leaves a non-volatile residue of high
viscosity, which is called vacuum residue.
Depending on the crude origin, the vacuum residue may
be used directly as bitumen without further processing. For
some crude oils though, or to meet particular specifications,
additional processing may be required, such as mild air
blowing of the residue. The air blowing process demands
careful selection and control of process temperature, air rate
and residence time to ensure consistent product. Sometimes
bitumens are produced by blending vacuum residue with
asphaltenes derived from the manufacture of lubricating oils.
For example, propane-precipitated asphalt (PPA) is commonly
used in the manufacture of bitumens when lubricating oils
are produced at the same refinery.
The selection of crude is an important aspect of bitumen
manufacture, requiring expertise and experience to yield
a satisfactory product – not all crude can be used to make
bitumen. Few of the nearly 1500 available crude petroleum
oils are suitable for the manufacture of good quality bitumen.
Within the Australian context, a very small number of crude
oils are able to be used to manufacture bitumen compliant
with the current Australian Standard.
Cutback bitumens are produced by diluting the paving grade
bitumen with a cutter or flux. Bitumen emulsions are made
in a colloid mill by dispersing paving grade bitumen in water
with the aid of an emulsifying agent.
For industrial bitumens, in order to produce a material
that will soften at a higher temperature than paving grade
bitumen of equivalent penetration, severe air blowing is
required. The product is therefore also known as ‘air-blown’
or ‘oxidised’ bitumen. Typically the blower feedstock has a
lower initial boiling point than for paving grade bitumens. It
is this, combined with severe blowing, that gives industrial
bitumens their special physical properties.
The production of high quality bitumen relies on a combination
of skills, experience and modern refinery technology. These
are used extensively to ensure the suitability of feedstocks
and to monitor and control all stages of the process.
Storage
Bitumen is stored at refineries and large depots in large
permanent tanks made of mild-steel plate, with capacities of
between 100 and 10,000 tonnes. Steam or hot oil is pumped
through heating coils in the heavily insulated tanks so that
the bitumen remains fluid. Smaller depots and big users
store bitumen in small permanent or semi-mobile tanks of up
to 60 tonnes capacity, typically heated by electricity or flame
heater tubes.
Distribution
As bitumen cools, it gradually becomes unworkable.
Therefore the delivery of paving grade bitumen not only calls
for the supply of bitumen to be provided at the right quality
and quantity at the right time, but the product must also be
kept between 150°C-190°C throughout the supply chain.
When it is loaded into a road tanker, the temperature can
drop by about 7°C-10°C and continue to fall by a further one
or two degrees per hour while in transit.
Road tankers with capacities of between 10 and 40 tonnes
are normally used to take most of the bitumen from the
refineries. They have insulated single-compartment tanks,
usually with some kind of heating such as heating tubes.
To transport bitumen to intermediary depots with reheating
facilities, insulated rail cars are sometimes used. Their
capacity ranges from 10 tonnes to 50 tonnes and they are
also fitted with electric heaters or direct oil-fired flame tube
heaters. When bitumen is moved by sea, it can be shipped
in a variety of vessels from 300 tonne barges to ocean-going
tankers of up to 30,000 tonnes capacity. The temperature of
the hot-loaded bitumen is maintained by high pressure steam
or hot oil passing through coils in the bitumen tanks.
Manufacturing Process
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Crude Oil
Atmospheric
Distillation
Severe Air
Blowing
Main
Refinery
Processing
Industrial
Bitumen
Bitumen
Emulsion
Polymer Bitumen
Emulsion
Polymer
Modified
Binder
Cutback
Bitumen
Fluxed
Bitumen
Paving Grade
Bitumen
Emulsification
Polymer
Mixing
Blending
Cutter Oil
Flux Oil
Water and
Emulsification
Agent
Wax Distillate
Vacuum
Distillation
Mild Air
Blowing
Vacuum
Residue
300° 350°C
350° 390°C
220° 260°C
Light Distillate:– Naphtha, Kerosene, Gas-oil
Atmospheric Distillation
The crude oil is split into
different boiling-point fractions.
Vacuum Distillation
Atmospheric residue is split into different
boiling-point fractions.
Air Blowing
By blowing air through bitumen at high
temperature under controlled conditions,
the heavy molecules are enlarged.
Emulsification
In an emulsion mill bitumen is dispersed
in water; chemicals are also added to
stabilise the emulsions.
Mixing
High energy mixing process to
disperse polymer into bitumen.
Blending
The viscosity of bitumen is reduced by
blending in various amounts of flux oil (solvents).
Figure 8: A refinery process diagram illustrating a
typical off-take for bitumen products.

12 13
Bitumen Basics
Before test
Dial set at zero
Time = 0 seconds
Dial reading
Time = 5 seconds
100g
Sample
Needle set just touching surface
Needle position after test =
dial reading in tenths of a millimetre
Water bath
heated
to 25°C
After test
14 Test Procedures
Characteristics
The main bitumen characteristics of interest are its viscosity
and its ability to be handled safely.
Viscosity: the degree of fluidity of the bitumen at a
standard test temperature. The viscosity of bitumen varies
according to its temperature; therefore when comparing
grades of bitumen, it is essential to carry out tests at
standard temperature.
Safety: to ensure that bitumen may be used safely, it
is critical that its flash point occurs at a much greater
temperature than that at which road construction work is
carried out. The flash point is the temperature at which the
heated bitumen will release fumes that will ignite (flash) in
the presence of a naked flame or a spark.
Test Development
Experience in using bitumen in engineering projects has led
to the adoption of certain test procedures that are indicative
of the characteristics that identify adequate performance.
However, there are two important points to be taken into
account when considering these test procedures.
1. Strict adherance to the specified test procedures.
2. Different specifying authorities use different standard test
procedures.
Some of the tests have evolved with the development of
the industry and are empirical methods. Consequently it is
essential that they are carried out in strict compliance with
the recommended procedures if they are to be accurate
measurements of the bitumen’s properties. Modern
technology is continually being employed by major bitumen
manufacturers at their research centres and in industry-
sponsored university research projects to find new ways of
measuring the physical properties of bitumen, and translating
these into specifications relating to road performance.
Specifying Authorities
Various organisations representing bitumen manufacturers
and users have laid down standard test procedures. Major
test methods specifiers are:
SA Standards Australia
Austroads The association of Australian and New
Zealand road transport and traffic authorities
AusSpec Joint Venture between Standards Australia
and the Institute of Public Works Engineering
Australia (IPWEA)
ASTM American Society for Testing and Materials (USA)
AASHTO American Association of State Highway and
Transportation Officials (USA)
DIN Deutsche Industrie Norm (Germany)
IP Institute of Petroleum (UK)
LCPC Laboratoire Central des Ponts et Chaussées
(France)
Paving Grade Bitumens
The test procedures used for paving grades of bitumen are
as follows:
Penetration Test: used to determine the consistency of
bitumen by measuring the distance that a standard needle
will penetrate vertically into a sample under specified
conditions of loading, temperature and time, i.e. load of 100g
at a temperature of 25°C for 5 seconds, reported in tenths of
a millimetre.
Figure 9: The penetration test as applied to bitumen.
Vacuum viscometer Gravity viscometer
To vacuum
Vent to atmosphere
Timing marks
Sample
Water bath
heated to 60°C
Water bath
heated
to 135°C
Upper
filling mark
Sample
Timing marks
Lower
filling mark
basics
15
Viscosity: is a more scientific measure of consistency
than Penetration. Various tests are used to measure
the resistance to flow of bitumen and to thereby define
its consistency. Results are given in units of Poise (P),
centistokes (cSt) or Pascal seconds (Pa s) as standard
units of measurement, the relationship between these
units depending on the specific gravity of the bitumen.
Different types of viscometers are used according to the
type of bitumen being tested and the preferences of local
specifying authorities.
The capillary tube viscometer with a means of applying a
partial vacuum is most commonly used for testing paving
grade and cutback bitumens at 60°C. The time taken for the
bitumen to flow between two points is taken and multiplied
by a calibration factor to give a value in Pascal seconds.
A vacuum is sometimes not required when testing paving
grade bitumen at 135˚C as the bitumen is fluid enough to
pass through the tube within a reasonable time under gravity
alone. The time taken for its passage is also multiplied by a
calibration factor and the result is expressed in Pascal seconds.
Another type of viscometer used for cutbacks and bitumen
emulsions is the efflux viscometer. This measures in
seconds the time a specified quantity of bitumen takes
to flow through an orifice of specified dimensions under
standard temperature conditions.
A fourth viscometer is the Brookfield Viscometer. A spindle
is suspended in a sample of bitumen. When the spindle
is twisted, the resistance to rotation is recorded through a
calibrated spring connected to a dial where the reading is
taken. Modern Brookfield Viscometers utilise digital displays
which directly show the viscosity of the material being tested.
Figure 10: The recognised methods used to measure viscosity.
Flash Point: used to measure the temperature to which a
sample of bitumen may be safely heated by establishing the
temperature at which a small flame causes the vapour above
the sample to ignite or flash. Various methods may be used
but the most common is the Cleveland Open Cup (COC)
test in which a brass cup filled with a specified amount of
bitumen is heated and a flame is passed over the top at
specified intervals of time. The flash point is the temperature
reached when the vapour causes an instantaneous flash.
A modified Pensky-Martens closed tester is used in the
Australian Standard test.
Figure 11: This test establishes the temperature at which a
sample of bitumen will ignite, i.e. flash point.
Heat source
Thermometer Temperature is noted
when flash occursVapour rising from sample
Cleveland brass cup
Naked flame to be
passed over sample
at specified intervals

14 15
Bitumen Basics
Thermometer
Condenser
Water coolant supply
Draught shield
Sample
heated to 360°C
Heat source
Wire gauze
Chimney
Water bath heated to 15°C Three samples set up for test
Mark indicates start of test
Samples are drawn through bath at a speed of 5cm per minute
Each failure is
indicated here
Thermometer Temperature is
noted at end of test
When ball
has dropped
a previously set
specified distance
test has ended
Balls
Ring
Sample
Water
Heat source
16
Ductility: gives an indication of the extent to which a sample
of the material can be stretched before breaking. A standard
briquette of bitumen, placed in a mould in a water bath heated
to 15°C, is pulled apart, usually at a speed of 5 cm per minute.
The length of the thread of bitumen at the moment when it
breaks, expressed in centimetres, is the ductility of the sample.
Figure 12: Ductility testing of bitumen samples:
Above: illustrates the position at the start of the test, and
Below: the points of failure.
Solubility and the Presence of Insolubles: indicates the
degree of contamination of the bitumen by other matter
and therefore the presence of pure bitumen. The Australian
test measures the percentage of matter that is insoluble in
toluene.
Effect of Heat and Air: is determined to simulate the
conditions obtained when the bitumen is used to
manufacture hot-mix. In the Rolling Thin Film Oven Test a
moving film of bitumen is heated in an oven at 163°C for
60 minutes. The viscosity is measured before and after
treatment.
Softening Point: a measurement of the temperature at
which a sample of bitumen held in a ring in a water bath
allows a steel ball of specified weight to fall to a point at a
specified distance below it. It is used as an indication of the
temperature at which bitumen has a particular viscosity – or
more simply, the temperature at which it softens.
Figure 13: The Softening Point test (‘Ring and Ball Test’)
measures the temperature at which bitumen has a particular
viscosity.
Cutback Bitumens
For cutback bitumens, in addition to the viscosity and flash
point tests, the following test is included in specifications:
Distillation test: a measured quantity of cutback is heated
to 360°C in a distillation flask. The volatile constituents
vaporise and pass into a water-cooled condenser flask where
they are measured to show the percentage of the volume
of the cutback that has been driven off. This indicates the
volatility of the cutback. The material that remains in the
distillation flask is treated as paving grade bitumen for further
testing for viscosity and solubility.
Figure 14: The Distillation test indicates the volatility of a
sample of cutback bitumen.
Bitumen Emulsions
Bitumen emulsions are subject to their own test procedures.
Some of the tests used for determining their properties are
as follows:
Consistency: Also known as the Engler Viscosity test, this
measures the rate of flow of the bitumen emulsion at 25°C.
The emulsion is heated to 25°C and poured into a standard
container. The time taken by 200mL of emulsion to pass
through a standard orifice at the bottom of the container is
measured.
Water Content test: determines the weight percent of
water in an emulsion. This can be performed by Dean and
Stark distillation or Karl Fischer titration. In the Dean and
Stark distillation, a sample is heated with a solvent that is
immiscible with water. During the distillation process, the
solvent and the water are separated in a trap so that the
amount of water can be measured. In the Karl Fischer water
content method, the emulsion is dissolved in a solvent and
titrated with a Karl Fischer reagent, which reacts with the
water in the emulsion. The amount of Karl Fischer reagent
consumed is used to determine the water content of the
emulsion.
Sedimentation test: indicates the extent to which the
components of an emulsion sample will separate during
storage. Samples are taken from the top and bottom of a
500mL sample that has stood undisturbed for three days.
The samples are tested for water content. The difference
between the water content of each sample is an indication
of the degree to which sedimentation has taken place.
Stone Coating Ability and Water Resistance test: it is
essential that a bitumen emulsion stands up to the action of
being mixed with aggregates, coat them as completely as
possible and not be washed off by any water that may fall on
it once the mixing is completed. This test shows the extent
to which a sample meets these requirements. It involves
coating a sample of aggregate with emulsion, spraying
it with water until the water coming from it is clear. The
coating on the sample is assessed.
Particle Charge test: identifies the charge on the bitumen
particles in an emulsion. A positive and a negative electrode
are left in a sample of emulsion for half an hour and an
electric current applied. If there is bitumen deposited on the
negative electrode at the end of the test the emulsion is
cationic; if bitumen is deposited on the positive electrode,
the emulsion is anionic.
Sieve Residue test: shows the presence of coarse binder
particles in the emulsion. These particles may be in the
form of relatively large globules or strings and may indicate
instability or result in poor coating performance or clogging
of equipment. The sample is strained through a 150µm sieve
and the percentage mass of emulsion retained on the sieve
is calculated and reported as sieve residue.
Residue from Evaporation test: indicates the percentage
mass of binder present in an emulsion. An emulsion sample
is heated so that water and other volatile components are
evaporated. Residue from evaporation is calculated from the
mass of the sample and residue after evaporation.
.
basics
17
Figure 15: The ‘Dean
and Stark test’
(‘Water Content
Test’) records the
percentage volume
of water in a bitumen
emulsion
Water
coolant
supply
Solvent
Heat source
Water
content
collected
here
Sample with
solvent mix

16 17
Bitumen Basics
18 Optimising Bitumen Performance
Background
Petroleum based bitumen is a product of consistently
high quality. Its production involves a heavy investment
in high-technology equipment and a commitment to
quality management at all stages of crude oil selection,
manufacture, blending, storage and distribution. By retaining
and checking samples of consignments of bitumen, the
composition and quality of the bitumen at the time it was
delivered to the contractor can be confirmed.
The actual performance of the bitumen when it is doing its
job is just one part of the total performance of an asphalt
mixture or sprayed seal. Asphalt performance depends on a
number of factors, including the design of the mixture, the
way it was mixed, the quality of mineral aggregate used and
how it was laid and compacted. Sprayed seal performance
depends on similar factors and can be significantly affected
by weather conditions at the time of spraying and the
cleanliness of the aggregate. As bitumen is an integral part
of both asphalt mixtures and sprayed seals, advice on how
to avoid and correct errors would need to cover many factors
and types of applications. This subject is outside the scope
of this booklet.
However, it is possible to put forward the following essential
guidelines to optimising the performance of bitumen, mainly
in hot mix asphalt, on the basis of what is known about
bitumen itself. Some of the points are mentioned elsewhere
but they have been repeated in this section for convenient
reference.
General Advice
Minimise the time during which hot bitumen is exposed
to air. Bitumen hardens and loses some of its adhesive
property when it is exposed to a combination of air and
excessive heat. Careless mixing of bitumen and aggregate
is an example of a practice that exposes bitumen to the air
and heat for longer than the minimum time required to coat
the aggregate. It is therefore likely to reduce the bitumen’s
performance as an adhesive.
Keep bitumen dry and away from contamination by water at
all times. When hot bitumen comes into contact with water it
will foam. In extreme cases it will violently boil over from storage
vessels due to the presence of small quantities of water.
Keep bitumen within the range of temperatures
recommended for the type and grade. Bitumen solidifies
as it cools and becomes unworkable and the viscosity may
increase due to oxidation if it is overheated. Keep asphalt at
the lowest temperature that will permit it to be thoroughly
mixed, transported and compacted to the specified density.
The maximum bitumen storage temperature relating to the
grade should not be exceeded during the mixing process.
Temperature control is a major factor in the quality control of
asphalt mixes.
Avoid contaminating the bitumen, particularly with petroleum
based solvents that reduce the flashpoint and the viscosity,
and increase the penetration. Just 0.1% diesel in an asphalt
mixture can lower the flash point and viscosity, and increase
the penetration significantly.
Stability is an essential quality in the performance of asphalt.
It depends on friction and cohesion within the mixture.
Too much bitumen will act as a lubricant for the aggregate
particles, reducing friction and therefore the stability of the
mix. The cohesion, or internal binding force in the mixture,
increases as the proportion of bitumen in the mixture is
increased, until it reaches the optimum. If the amount of
bitumen increases further, stability decreases. It is therefore
essential to ensure that the optimum proportion of bitumen
is used in any mixture.
To quote the Asphalt Institute of America directly: “Finished
mix should be frequently observed. No testing method or
device is as quick and convenient as the human eye.” The
following are useful examples of what can be seen by simple
observation. They can be treated as early warning signs that
further checks should be made:
• blue smoke coming from the mixture can indicate
overheating
• steam coming from the mixture indicates the presence of
too much moisture
• if the distribution of bitumen on the aggregate is not uniform,
the temperature in the mixing operation may be too low
• if the mixture looks stiff and dull rather than black and
shiny there may be too little bitumen in the mixture, or
overheating has excessively oxidised the binder
• if the mixture lies slumped on the floor of the truck the
mixture may contain too much bitumen
basics
19Glossary
AAPA – Australian Asphalt Pavement Association.
adhesion agent – A substance added to a bituminous binder
to improve adhesion between the binder and aggregate. The
term is usually applied to adhesion in the presence of water.
Also commonly known as an anti-stripping agent.
age hardening – Hardening of a bituminous binder due to
loss of volatiles and oxidation of the binder resulting from
exposure to weather over a period of time.
aggregate – A material usually produced by crushing rock,
slag, gravel, sand or similar material and screened to provide
a specific size distribution.
air voids – The spaces within the bulk of a material, such as
an asphalt mix, which is not occupied by solid matter or filled
with bituminous binder.
ALGA – Australian Local Government Association.
anionic bitumen emulsion – A bituminous emulsion in which
the suspended bitumen droplets are negatively charged.
anti-foaming agent – A substance (e.g. silicone oil) added
to bitumen to reduce the surface tension and hence the
frothing tendency of hot bitumen in the presence of water.
application rate (aggregate) – The amount of aggregate
spread in a sprayed seal expressed as square metres per
cubic metre (m2
/m3
). Commonly known as the aggregate
spread rate or coverage.
application rate (binder) – The amount of bituminous
binder applied in a sprayed seal expressed as litres per
square metre (L/m2
), usually expressed at 15°C. Commonly
known as the spray rate.
ARF – Australian Road Federation.
ARRB – Australian Road Research Board, now known as
ARRB Group Limited.
asphalt – A mixture of bituminous binder and aggregate,
with or without mineral filler. Usually produced hot in a
mixing plant and delivered, spread and compacted while hot.
Also known as hot mix or hot mix asphalt (HMA).
Asphalt Institute (AI) – An association of international
petroleum bitumen producers, manufacturers, and affiliated
businesses, based in the USA.
asphalt, dense-graded (DGA) – An asphalt comprised of
coarse and fine aggregates, filler and a bituminous binder,
which is placed hot and then compacted to a dense state
as a road pavement layer. The aggregate gradation of dense
graded asphalt is considered to be continuous and the
intimate interlocking of the aggregate particles is a major
factor in the strength of the compacted asphalt. Also known
as asphaltic concrete.
asphalt, hot rolled (HRA) – An asphalt material used as a
dense wearing course, basecourse or roadbase material and
which consists of a mixture of gap-graded coarse aggregate,
fine aggregates, filler and bituminous binder. Common in
the UK.
asphalt, lake – A highly viscous natural bitumen found in
well-defined surface deposits e.g. Trinidad Lake Asphalt.
asphalt, open-graded (OGA) – An asphalt comprised
of a large proportion of a single size aggregate, filler and
bituminous binder, which has an interconnecting voids
content of about 20% to 25%. Also known as porous asphalt
and drainage asphalt.
asphalt, stone mastic (SMA) – An asphalt with a high
coarse aggregate content and a high volume of both filler and
bituminous binder, the strength of which is predominantly
provided by stone-on-stone contact of the coarse aggregate
particles. Also known as Splitt Mastic Asphalt.
asphaltenes – High molecular weight compounds in bitumen
which are soluble in carbon disulphide, but insoluble in
aromatic-free low-boiling petroleum solvents, such as n-heptane.
asphaltic cement – North American term for bitumen.
asphaltic concrete – See asphalt, dense-graded (DGA).
atmospheric residue (atres) – The residue obtained in the
atmospheric distillation of crude petroleum oil.
Austroads – The association of Australian and New Zealand
road transport and traffic authorities.
AustStab – Australian Stabilisation Industry Association.
base course – One or more layers of material immediately
below the wearing course of a pavement. Also known as
base or binder course.

18 19
Bitumen Basics
20
binder – A material that is used to hold aggregate particles
together or to a substrate, such as bitumen in asphalt and
sprayed seals, or cement in concrete.
bitumen – A viscous liquid or solid, consisting essentially
of hydrocarbons and their derivatives, which is substantially
soluble in organic solvents, such as toluene and carbon
disulphide, and is substantially non-volatile and softens
gradually when heated. It is black or brown in colour and
possesses waterproofing and adhesive properties. It is either
obtained by refinery processes from petroleum or is found
as a natural deposit or as a component of naturally occurring
asphalt, in which it is associated with mineral matter. Also
known as asphalt in North America.
bitumen emulsion – A liquid mixture in which bitumen
is suspended as small droplets in water by means of
emulsifying and stabilising agents.
bitumen, blown – Bitumen through which air has been
passed (blown) at high temperature for the purpose of
altering its viscosity characteristics.
bitumen, cutback – See cutback bitumen
bitumen, fluxed – A bitumen to which a flux oil has been
added to provide a long-term reduction in its viscosity.
bitumen, industrial grade – See bitumen, oxidised.
bitumen, oxidised – Bitumen, to which other refinery
products such as paraffinic oils may have been added, that
has been subjected to a prolonged blowing process to
substantially change its viscosity characteristics. Also known
as industrial grade bitumen.
bitumen, paving grade – Bitumen manufactured specifically
for use in road pavement applications.
bitumen, petroleum – Bitumen obtained from crude
petroleum oil by a refinery processes.
bitumen, straight run – Bitumen produced from crude
petroleum oil solely by a process of distillation (atmospheric
& vacuum). Also known as residual bitumen.
bituminous – A material that resembles or contains bitumen.
bituminous slurry – A mixture of bitumen emulsion (with
or without added polymer modifier), mineral aggregate,
filler, additives and water properly proportioned to form a
slurry which can be spread evenly on a road surface (as in
bituminous slurry surfacing).
blowing – A refinery process involving the blowing of air
through bitumen, usually at high temperature, to alter its
viscosity characteristics. Also known as air blowing.
blown bitumen – See bitumen, blown.
boil over – The sudden overflow of a tank contents caused
by the rapid evaporation of water within hot bitumen.
break (of a bitumen emulsion) – The separation of a
bitumen emulsion into free bitumen and water, which occurs
as a result of coagulation of the dispersed bitumen droplets
to form a continuous phase.
cape seal – A surfacing treatment incorporating the
placement of a bituminous slurry over a sprayed seal to
provide an asphalt-like appearance.
cationic bitumen emulsion – A bituminous emulsion in
which the suspended bitumen droplets are positively charged.
chip seal – See sprayed seal.
cohesion – The magnitude of internal forces that resist the
separation of a material into its constituent particles.
cold mix – A mixture of bituminous binder and aggregate,
with or without added filler, which is produced warm or
cold in a mixing plant and can be delivered in a workable
condition suitable for stockpiling, spreading and compaction.
It is typically used in areas where it is impractical to do repair
work using hot mix.
compaction – The process of producing a closer packing
of aggregate and filler particles in asphalt by rolling or other
mechanical means. Usually aimed at achieving a desired
voids content.
consistency – A general term describing the relative
resistance to deformation or flow of a semi-fluid or plastic
material.
continuous grading – An aggregate grading or particle size
distribution where all sizes or fractions from the maximum
particle size down are represented. The grading curve has a
smooth concave shape without abrupt changes in slope.
basics
21
creep – The slow deformation of a material, such as asphalt,
generally measured under constant stress.
crumb rubber – Either natural or styrene butadiene rubber
recovered by comminuting used vehicle tyres into small
crumbs which are then graded to conform to a specified size
range for use as a bitumen modifier.
crumb rubber modified seal (CRM seal) – A sprayed seal
in which the binder consists of bitumen modified by the
incorporation of crumb rubber.
cure (of an emulsion) – The increase in cohesive strength
of a bituminous binder following application in emulsified
form, usually due to the progressive loss of water and other
volatile materials following emulsion break.
cutback bitumen – Bitumen to which a suitable volatile
diluent, known as a cutter oil, has been added for the
purpose of temporarily reducing its viscosity.
cutter oil – A light petroleum distillate, such as kerosine,
which is added to bitumen to temporarily reduce its viscosity
(cutback bitumen).
dense-graded asphalt – See asphalt, dense graded.
DIER Tas – Department of Infrastructure, Energy and
Resources, Tasmania.
distillation, atmospheric – A refinery process that
separates components in a crude petroleum oil by virtue
of their different boiling points. Atmospheric distillation is
carried out at normal atmospheric pressure.
distillation, vacuum – A refinery process that separates
components in a crude petroleum oil by virtue of their
different boiling points. Vacuum distillation is carried out at
reduced pressure to separate higher boiling components
that would otherwise decompose if higher distillation
temperatures and normal atmospheric pressures were used.
Vacuum distillation is usually carried out on the residue
obtained from atmospheric distillation.
DOTARS – Australian Department of Transport and Regional
Services.
double seal – A sprayed seal constructed by applying two
successive sprayed seals. Usually, the first sprayed seal uses
a larger aggregate size than the second sprayed seal.
DCI NT – Department of Construction and Infrastructure,
Northern Territory.
drainage asphalt – See asphalt, open graded.
DTEI SA – Department for Transport, Energy and
Infrastructure, South Australia.
DTMS ACT – Department of Territory and Municipal
Services, Australian Capital Territory.
ductility – The characteristic of a bituminous binder that
allows it to be elongated without rupture when stretched.
Ductility values are defined as the distance to which a
standard-sized sample of bituminous binder can be elongated
before the thread so formed breaks under standard specified
test conditions.
ductility recovery – A modification of the ductility test
whereby the sample is stretched to a thread of fixed length
and then cut in the middle. The distance between the ends
of the half threads, which develops after a standard period
of time, is used to calculate the elastic recovery. It is usually
expressed as a percentage of the elongation length.
durability – The maintenance of performance properties of
bitumen and bituminous materials to traffic, weather and
other external factors. For bitumen, the measurement under
standard specified test conditions of the long term effect of
heat and air is known as the Durability and is based on the
accelerated aging of bitumen to determine the time required
for it to reach a specified viscosity level that has been
associated with distress in pavement surfacings.
dynamic shear rheometer (DSR) – An instrument that
measures the rheological properties, such as deformation
and flow characteristics, of bituminous binders.
dynamic viscosity – The ratio of shear stress to shear
(strain) rate of a fluid.
elastomer – A polymeric material that exhibits
predominantly elastic properties.
emulsifier – A chemical that stabilises an emulsion by
reducing the coalescence of dispersed droplets.
emulsion – A colloidal suspension of a liquid (the dispersed
phase) in another liquid (the continuous phase) in which it is
not soluble.

20 21
Bitumen Basics
22
emulsion, bitumen – See bitumen emulsion.
ethylene methyl acrylate (EMA) – A plastomeric polymer
used in the modification of bitumen.
ethylene vinyl acetate (EVA) – A plastomeric polymer used
in the modification of bitumen.
Eurobitume – European bitumen association.
filler – A finely divided mineral powder, which is normally
less than 0.075mm in size. Typically derived from crushed
aggregate, although cement and lime are also used as filler.
flash point – The lowest temperature at which the vapour of
a material momentarily catches fire when a flame is applied,
but does not continue to burn.
flux oil – A substantially non-volatile petroleum diluent, such
as automotive diesel fuel, which is used to produce a long-
term reduction in the viscosity of bitumen.
fluxed bitumen – See bitumen, fluxed.
foamed bitumen – Hot bitumen to which steam or water
has been added to temporarily greatly expand its volume by
creating a foamed state.
fog seal – See surface enrichment.
high stress seal (HSS) – A sprayed seal which is applied
specifically to withstand heavier than normal traffic loading
due to braking, accelerating and turning vehicles.
hot mix (HMA) – See asphalt.
IPWEA – Institute of Public Works Engineering Australia.
IRF – International Road Federation.
kinematic viscosity – The ratio of dynamic viscosity to
density of a material.
maltenes – Lower molecular weight compounds in bitumen
which are soluble in normal heptane.
microsurfacing – A bituminous slurry, which usually contains
polymer, that is capable of being applied in variably thick
layers for rut-filling, correction courses and wearing courses.
mineral aggregate – See aggregate.
mineral filler – See filler.
modulus – The ratio of a component of stress to a
component of strain. Also called stiffness.
multigrade bitumen – A bitumen produced in a special
refinery process to modify the temperature susceptibility
otherwise characteristic of normal bitumen. A multigrade
bitumen will exhibit a higher viscosity at a high service
temperature and a lower viscosity at a low service temperature
than an equivalent normal paving grade bitumen.
open-graded asphalt – See asphalt, open-graded (OGA).
particle size distribution – The percentages of the various
sizes of aggregate or filler as determined by sieving. Also
known as grading.
pavement – The road structure placed above the subgrade.
paving grade bitumen – See bitumen, paving grade.
penetration – An indication of the softness of a bituminous
binder and measured as the vertical distance penetrated by a
standard needle entering a bituminous binder sample under
specified conditions of load, time and temperature.
penetration index (PI) – The penetration index represents a
quantitative measure of the temperature susceptibility of
bitumen and is determined by calculation from two penetration
values determined at different temperatures. Alternative
equations exist that calculate PI from a combination of
penetration, softening point and viscosity measurements.
plastomer – A polymeric material that exhibits
predominantly plastic flow properties.
polybutadiene (PBD) – An elastomeric polymer used in the
modification of bitumen.
polyethylene (PE) – A plastomeric polymer used in the
modification of bitumen.
polymer – Long thread-like molecule made up from small,
repeating units or monomers. Molecular weight may range
from a few thousand to millions. Polymers typically used
in bitumen have molecular weights of several hundred
thousand.
basics
23
polymer modified binder (PMB) – A pre-formed blend of
bitumen, polymer and other additives made under carefully
controlled conditions and which has enhanced binder
performance for particular applications.
Portland cement – Hydraulic cement made by heating to
a high temperature a mixture of clay and limestone and
grinding the resulting clinker to a fine powder.
precoat – A precoat, or more accurately, an aggregate
precoating fluid, is a liquid that, when applied to the surface
of aggregate particles, serves to enhance the adhesion
of those particles to bituminous binders in sprayed seal
applications. Precoats can be water-based, neat diesel,
or more often a blend of bitumen with flux or cutter oils.
Adhesion agents may also sometime be added.
prime – An application of a bituminous material (primer)
to a prepared base as a preliminary treatment to a more
permanent surfacing. The role of a prime is to penetrate and
bind the substrate surface and provide a waterproof bonding
layer between the existing pavement and the subsequent
sprayed seal or asphalt layer.
primer – A bituminous material of low viscosity and low
surface tension used in priming. Often a cutback bitumen.
primer binder – A material which is more viscous than a
primer that is used to act both as a primer and binder and
used in primer sealing.
primer seal – A preliminary sprayed seal treatment intended
to carry traffic for an interim period, which is constructed
by applying a primer binder with a fine cover aggregate.
Typically applied to new granular pavements prior to the
placement of an asphalt overlay.
propane-precipitated asphaltenes (PPA) – Asphaltene
material obtained as a precipitate from a mixture of vacuum
residue in propane. Normally derived as a by-product of
lubricant base oil manufacture.
pyrophoric deposit – A deposit often found on the inside
surfaces of bitumen storage tanks and normally formed
in an oxygen depleted environment, which can be self-
heating when its temperature or the surrounding oxygen
concentration is increased.
reclaimed asphalt pavement (RAP) – Material reclaimed
from an asphalt pavement, usually by cold milling, and which
may be reutilised in new asphalt pavement layers.
reseal – A sprayed seal applied to a surface which has an
existing seal.
residual bitumen – See bitumen, straight run.
rheology – The study of flow and deformation of materials.
rheometer – An instrument for measuring the rheological
properties (deformation and flow characteristics) of
materials. May be used for creep tests, dynamic tests,
viscosity measurement, etc.
rolling thin film oven test (RTFOT) – A laboratory test to
simulate the ageing a bituminous binder will undergo in an
asphalt mixing plant.
RTA NSW – Roads and Traffic Authority, New South Wales.
rubber – See crumb rubber.
SA – Standards Australia.
sand – A non-cohesive granular material, usually under
2.36 mm in size, which results from the natural disintegration
of rock and consists mainly of mixtures of irregular or sub-
angular and rounded particles.
scrap rubber – See crumb rubber.
seal coat – See sprayed seal.
sedimentation – The process whereby the more dense
bitumen droplets settle out of the less dense continuous
aqueous phase of a bitumen emulsion to form a sediment.
segregation – The separation of polymer from bitumen,
usually during hot storage, which sometimes results in
polymer concentrations increasing in the top layers and
decreasing in the bottom layers of PMBs held in storage.
set up – To harden or cure, either by evaporation of volatiles
or natural oxidation by air.
single/double seal – A sprayed seal constructed by applying
a single application of bituminous binder followed by a
double application of aggregate.

22 23
Bitumen Basics
24
single/single seal – A sprayed seal constructed by applying
a single application of bituminous binder followed by a single
application of aggregate.
slurry seal – A surface treatment consisting of a thin layer of
bituminous slurry, usually without added polymer.
slurry surfacing – See bituminous slurry.
softening point – The temperature at which a bituminous
binder softens under standard specified conditions. Usually
determined by the ring and ball softening point test,
which measures the temperature at which a disc of the
binder softens sufficiently to allow a standard steel ball,
initially placed on the surface, to fall through the disc for a
prescribed distance.
sprayed seal – A thin layer of bituminous binder sprayed
onto a pavement surface followed by the application of
a layer of single-sized aggregate. Also known as surface
dressing (UK) and chip seal (NZ).
stabilisation – The treatment of a road pavement or
subgrade material by the introduction of a bituminous binder
to improve its engineering strength.
stiffness – See modulus.
stone mastic asphalt (SMA) – See asphalt, stone mastic (SMA).
straight-run bitumen – See bitumen, straight run.
strain alleviating membrane (SAM) – A sprayed seal
in which the bituminous binder is formulated to reduce
reflection cracking, usually by the incorporation of polymer.
Used to waterproof an underlying cracked pavement surface.
strain alleviating membrane interlayer (SAMI) – Similar
to a SAM, but provided as an interlayer between pavement
layers to reduce the likelihood of cracks reflecting through
the top asphalt layer from the underlying pavement.
styrene-butadiene rubber (SBR) – An elastomeric polymer
used in the modification of bitumen, the polymer backbone
of which is made up of randomly distributed styrene and
butadiene monomers. Also known as synthetic rubber.
styrene-butadiene-styrene (SBS) – An elastomeric polymer
used in the modification of bitumen, the polymer backbone of
which is made up by joining polystyrene, polybutadiene and
polystyrene polymer blocks in either a linear or radial formation.
subbase – The material laid on the subgrade to either make
up additional pavement thickness, to prevent intrusion of the
subgrade into the base, or to provide a working platform for
placement of the base course.
subgrade – The soil foundation below a pavement.
surface enrichment – A light application of bituminous
binder to an existing sprayed seal for the purpose of
increasing its binder volume and extending its service life.
tack coat – A light application of a bituminous binder to a
prepared base as a preliminary treatment to promote surface
adhesion of the subsequent asphalt layer.
tar – A viscous solid, semi-solid, or liquid material, black in
colour and having adhesive properties, which is typically
obtained by the destructive distillation of coal, wood or shale.
temperature susceptibility – The change in viscosity of
a bituminous binder with change in temperature. A high
temperature susceptibility indicates a large change in
viscosity with temperature.
TMR – Department of Transport and Main Roads,
Queensland.
vacuum residue (vacres) – The residue obtained in the
vacuum distillation of atmospheric residue.
VicRoads – The Victorian road authority.
viscoelasticity – The rheological characteristic of a
bituminous binder represented by both viscous and elastic
behaviour, i.e. behaviour which is like that of both a solid and
a liquid, in response to an applied stress.
viscometer – An instrument for measuring the viscosity of a
material.
viscosity – The property of a fluid whereby, through internal
friction, it resists movement and expressed as the stress
divided by the strain rate.
voids – See air voids.
wearing course – The surface layer of a pavement that is in
direct contact with traffic.
For advice on which product to use to
meet your specific job requirements,
please contact us:
On the web:
roadsthatperform.com.au
By email:
bitumen.au@pumaenergy.com
Technical Helpline:
1800 24 88 66
Or contact the Puma Bitumen sales
manager in your region.

Bitumen Basics
24
The information provided in this Guide is of a general nature and should only be used as a guide. Please contact Puma Bitumen staff to ensure you have access to the most
current information and for advice relating to any particular circumstances. Puma Energy (Australia) Bitumen Pty Ltd makes no warranty as to the completeness or accuracy
of the information provided and, to the fullest extent permitted by applicable law, Puma Energy and its subsidiaries are not liable for any costs, loss or damage incurred in
connection with use of the information provided in this Guide. The material contained in this Guide is protected by copyright. Puma Energy and Olexobit are registered trade
marks of Puma Energy. August 2015.
© 2015 Puma Energy (Australia) Bitumen Pty Ltd, ABN 78 147 981 020, Level 1, North Tower, Green Square, 515 St Pauls Terrace, Fortitude Valley QLD 4006.
Puma Bitumen Locations
Head Office
Puma Energy Australia
Level 1, North Tower, Green Square
515 St Pauls Terrace
Fortitude Valley, QLD 4006
T 1300 726 706
F 1300 723 906
PO Box 95, Fortitude Valley, QLD 4006
Queensland/Northern Territory
Puma Bitumen Townsville
1 Benwell Road
South Townsville, QLD 4810
T 07 4724 9500
PO Box 2267, Townsville, QLD 4810
New South Wales
Puma Bitumen Sydney
Suite 2.10, Aero 247 Building 247
Coward Street, Mascot, NSW 2020
Tasmania
Puma Bitumen Selfs Point
Selfs Point Road, New Town, TAS 7008
T 03 6278 1310
F 03 6278 2205
PO Box 282, Moonah, TAS 7009
Victoria / South Australia
Puma Bitumen Altona
55 Toll Drive, Altona North, VIC 3025
T 03 8368 8700
F 03 8368 8701
PO Box 495, Altona North, VIC 3025
Western Australia
Puma Bitumen Kwinana
Mason Road, Kwinana, WA 6966
T 08 9419 9712
F 08 9419 9820
PO Box 2131, Rockingham, WA 6167

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