basics
basics Index 03 Introduction and Historical Perspective 04 Bitumen Sources and Types 07 Applications 12 Manufacturing Process 14 Test Procedures 18 Optimising Bitumen Performance 19 Glossary 26 BP Bitumen Australia
Introduction and Historical Perspective The description of bitumen as ‘mankind's oldest engineering material’ can be supported by a considerable amount of
the lakes of asphalt in Trinidad useful for re-caulking their ships for the return voyage. Apart from maritime usage,
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.
bitumen was used mainly for medicinal, cosmetic and crop protection purposes.
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 f orm 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 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 f rom 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 tar from local coal-gas works led to their 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 sc ale. 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. Oustide the USA, the word asphalt means a mixture of bitumen and mineral aggregates laid as a road surface.
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basics 04
Bitumen Sources and Types 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.
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.
05 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.
It consists essentially of hydrocarbons and typically comprises 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.
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%.
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:
The three broad classifications for crude oils are:
• applying heat
• bitumen based
• dissolving it in petroleum solvents
• paraf fin based
• dispersing it in water (emulsification).
• 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 tar sands and so-called asphalt lakes. It is commonly mixed with varying proport ions 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
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. 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 waterproofing 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.
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 highspeed 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.
40 micrometres Limit of visibility to the naked eye
100 micrometres Grain of salt
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 cur ing (SC).
70 micrometres Diameter of human hair 25 micrometres White blood cells
8 micrometres Red blood cells 2 micrometres Bacteria
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.
basics Applications
06
Fine
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:
Coarse
Figure 3: Microscopic representation of emulsion structures.
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 gr ade 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
Anionic
Cationic
ARS
CRS
Rapid setting
AMS
CMS
Medium setting
ASS
CSS
Slow setting
The four major factors involved in handling bitumen are: • the high handling temperatures and the need for purposedesigned 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 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
• 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.
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.
07 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 t he 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%. GENERAL ROAD CONSTRUCTION AND MAINTENANCE APPLICATIONS Cutb ack grades Emulsions Modified
Pavin g grades Example s of use
C50
C170
C320
bitumens
C600
Low High viscosity viscosity
Cutback manufacture Emulsion manufacture Hotmix asphalt Sprayed seals Tack coat
Table A: This table defines some typical road construction and maintenance applications for different types of bitumen.
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09
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.
Direction of load
Bitumen supplies are ordered daily to meet the production schedules on the road gangs' programs for the following Wearing course
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
Tack coat
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.
Base course
Tack coat
Sub-base
Formation level Subgrade (natural soil)
Figure 4: Distribution of load through a bituminous road
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11
Road Recycling
COMPOSITION OF ROAD SURFACE
The techniques of road recycling reclaim the materials used to build roads. They offer benefits in terms of reduced Dense-graded Asphalt Bitumen content % Air voids content %
Hot Rolled Asphalt
StoneMastic Asphalt
Open-graded Asphalt
4-7%
6-9%
8-12%
5-7%
3-5%
3-5%
3-5%
18-20%
Table B: Asphalt mixture compositions
s
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).
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.
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 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 t o 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 truckmounted mixing plant.
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 bitumensaturated 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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Manufacturing Process 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°C390°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 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’
13 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.
Light Distillate:– Naphtha, Kerosene, Gas-oil
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.
Crude Oil
300° 350°C
Atmospheric Distillation
Storage Bitumen is stored at refineries and large depots in large permanent tanks made of mild-steel plate, with capacities of
Industrial Bitumen
Wax Distillate
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
Severe Air Blowing
350° 390°C
Water and Emulsification Agent Vacuum Distillation
Vacuum Residue
Bitumen Emulsion
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 pr essure steam or hot oil passing through coils in the bitumen tanks.
Main Refinery Processing
Polymer Bitumen Emulsion Emulsification
220° 260°C
Polymer
Air Blowing
Polymer Modified Binder
Atmospheric Distillation The crude oil is split into differentboiling-pointfractions.
Mixing
Vacuum Distillation Atmospheric residue is split into different boiling-pointfractions.
Air Blowing By blowing air through bitumen at high temperatureundercontrolled conditions, the heavy molecules are enlarged.
Cutback Bitumen
Emulsification In an emulsion mill bitumen is dispersed in water; chemicals are also added to stabilisetheemulsions.
Cutter Oil Flux Oil
Fluxed Bitumen
Mixing High energy mixing process to dispersepolymerintobitumen.
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.
Blending
Paving Grade Bitumen
basics 14
Test Procedures
15 Standards Australia
Characteristics
SA
The main bitumen characteristics of interest are its viscosity and its ability to be handled safely.
Austroads The association of Australian and New Zealand road transport and traffic authorities
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
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)
heated bitumen will release fumes that will ignite (flash) in the presence of a naked flame or a spark.
LCPC
Laboratoire Central des Ponts et Chaussées (France)
Test Development
Paving Grade Bitumens
Experience in using bitumen in engineering projects has led to the adoption of certain test procedures that are indicative
The test procedures used for paving grades of bitumen are as follows:
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 industrysponsored 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:
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. Before test Dial set at zero
Time = 0 seconds
After test Dial reading
Time = 5 seconds
100g
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.
Vacuum viscometer
Gravity viscometer
To vacuum
Vent to atmosphere Upper filling mark Water bath heated to 60°C
Sample Water bath heated to 135°C
Timing marks
Timing marks
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.
Lower filling mark
Sample
Figure 10 a) b): 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.
Thermometer
Temperature is noted when flash occurs
Vapour rising from sample Cleveland brass cup Naked flame to be passed over sample at specified intervals
Water bath heated to 25°C Sample Needle set just touching surface
Needle position after test = dial reading in tenths of a millimetre Heat source
Figure 9: The penetration test as applied to bitumen. Figure 11: This test establishes the temperature at which a sample of bitumen will ignite, i.e. flash point.
basics 16
17 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.
Bitumen Emulsions Thermometer
Temperature is noted at end of test
Balls Ring
When ball has dropped a previously set specified distance test has ended
Sample Water
Water bath heated to 15°C
Three sample s setup for test
Heat source Mark indicates start of test
Samples are drawn through bath at a speed of 5cm per minute
Figure 13: The Softening Point test (‘Ring and Ball Test’) measures the temperature at which bitumen has a particular viscosity.
Cutback Bitumens Each failure is indicated here
Figure 12: Ductility testing of bitumen samples: Above: illustrates the position at the start of the test, and Below: the points of failure.
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
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
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
test measures the percentage of matter that is insoluble in toluene.
testing for viscosity and solubility.
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
Thermometer Water coolant supply Draught shield
Sample heated to 360°C Wire gauze
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
Chimney
Heat source
Figure 14: The Distillation test indicates the volatility of a sample of cutback bitumen.
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.
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.
Water coolant supply
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.
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.
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.
Bitumen emulsions are subject to their own test procedures.
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. 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.
.
Solvent Water content collected here Sample with solvent mix
Heat source
Figure 15: The ‘Dean and Stark test’ (‘Water Content Test’) records the percentage volume of water in a bitumen emulsion
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
Glossary 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.
19 asphalt, dense-graded (DGA) – An asphalt comprised of coarse and fine aggregat es, 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.
aggregate – A material usually produced by crushing rock, slag, gravel, sand or similar material and screened to provide
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
a specific size distribution.
UK.
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.
asphalt, lake – A highly viscous natural bitumen found in well-defined surface deposits e.g. Trinidad Lake Asphalt.
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
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.
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.
asphaltic cement – North American term for bitumen.
• if the distribution of bitumen on the aggregate is not uniform, the temperature in the mixing operation may be too low
ARF – Australian Road Federation
atmospheric residue (atres) – The residue obtained in the atmospheric distillation of crude petroleum oil.
• 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
ARRB – Australian Road Research Board, now known as ARRB Group Limited
• steam coming from the mixture indicates the presence of too much moisture
• if the mixture lies slumped on the floor of the truck the mixture may contain too much bitumen
asphaltic concrete – See asphalt, dense-graded (DGA).
Austroads – The association of Australian and New Zealand road transport and traffic authorities.
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.
AustStab – Australian Stabilisation Industry Association
Also known as hot mix or hot mix asphalt (HMA).
base course – One or more layers of material immediately
Asphalt Institute (AI) – An association of international petroleum bitumen producers, manufacturers, and affiliated businesses, based in the USA.
below the wearing course of a pavement. Also known as base or binder course.
basics 20
21 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.
slurry which can be spread evenly on a road surface (as in bituminous slurry surfacing).
creep – The slow deformation of a material, such as asphalt, generally measured under constant stress.
DPI NT – Department of Planning and Infrastructure Northern Territory
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.
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.
drainage asphalt – See asphalt, open graded.
crumb rubber modified seal (CRM seal) – A sprayed seal in which the binder consists of bitumen modified by the incorporation of crumb rubber.
DTMS ACT – Department of Territory and Municipal Ser vices Australian Capital Territory.
by the rapid evaporation of water within hot bitumen. break (of a bitumen emulsion) – The separation of a
cure (of an emulsion) – The increase in cohesive strength
bitumen emulsion into free bitumen and water, which occurs as a result of coagulation of the dispersed bitumen droplets to form a continuous phase.
of a bituminous binder following application in emulsified form, usually due to the progressive loss of water and other volatile materials following emulsion break.
cape seal – A surfacing treatment incorporating the placement of a bituminous slurry over a sprayed seal to provide an asphalt-like appearance.
cutback bitumen – Bitumen to which a s uitable volatile diluent, known as a cutter oil, has been added for the purpose of temporarily reducing its viscosity.
cationic bitumen emulsion – A bituminous emulsion in which the suspended bitumen droplets are positively charged.
cutter oil – A light petroleum distillate, such as kerosine, which is added to bitumen to temporarily reduce its viscosity (cutback bitumen).
DTEI SA – Department for Transport, Energy and Infrastructure: the South Australian State Road Authority.
blown bitumen – See bitumen, blown. boil over – The sudden overflow of a tank contents caused
bitumen, cutback – See cutback bitumen
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.
chip seal – See sprayed seal. bitumen, fluxed – A bitumen to which a flux oil has been added to provide a long-term reduction in its viscosity.
dense-graded asphalt – See asphalt, dense graded. cohesion – The magnitude of internal forces that resist the separation of a material into its constituent particles.
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.
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.
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
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
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.
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
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.
and flow characteristics, of bituminous binders.
DOTARS – Australian Department of Transport and Regional Services
emulsifier – A chemical that stabilises an emulsion by reducing the coalescence of dispersed droplets.
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.
emulsion – A colloidal suspension of a liquid (the dispersed phase) in another liquid (the continuous phase) in which it is not soluble.
dynamic viscosity – The ratio of shear stress to shear (strain) rate of a fluid. elastomer – A polymeric material that exhibits predominantly elastic properties.
basics 22
23 emulsion, bitumen – See bitumen emulsion
mineral filler – See filler.
ethylene methyl acrylate (EMA) – A plastomeric polymer used in the modification of bitumen.
modulus – The ratio of a component of stress to a component of strain. Also called stiffness.
ethylene vinyl acetate (EVA) – A plastomeric polymer used in the modification of bitumen.
filler – A finely divided mineral powder, which is normally
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.
less than 0.075mm in size. Typically derived from crushed aggregate, although cement and lime are also used as filler.
open-graded asphalt – See asphalt, open-graded (OGA).
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.
particle size distribution – The percentages of the various sizes of aggregate or filler as determined by sieving. Also known as grading.
Eurobitume – European Bitumen Association.
flux oil – A substantially non-volatile petroleum diluent, such as automotive diesel fuel, which is used to produce a longterm reduction in the viscosity of bitumen.
pavement – The road structure placed above the subgrade.
fluxed bitumen – See bitumen, fluxed.
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.
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.
paving grade bitumen – See bitumen, paving grade.
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.
IPWEA – Institute of Public Works Engineering Australia. IRF – International Road Federation.
polybutadiene (PBD) – An elastomeric polymer used in the modification of bitumen.
kinematic viscosity – The ratio of dynamic viscosity to density of a material.
polyethylene (PE) – A plastomeric polymer used in the modification of bitumen.
maltenes – Lower molecular weight compounds in bitumen which are soluble in normal heptane.
polymer – Long thread-like molecule made up from small, repeating units or monomers. Molecular Weight may range
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.
from a few thousand to millions. Polymers typically used in bitumen have molecular weights of several hundred thousand.
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.
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
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 selfheating when its temperature or the surrounding oxygen concentration is increased. QDMR – Queensland Department of Main Roads.
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 subangular 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.
basics 24
25 single/single seal – A sprayed seal constructed by applying a single application of bituminous binder f ollowed 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.
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. vacuum residue (vacres) – The residue obtained in the vacuum distillation of atmospheric residue.
stiffness – See modulus. VicRoads – The Victorian road authority. stone mastic asphalt (SMA) – See asphalt, stone mastic (SMA). straight-run bitumen – See bitumen, straight run.
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
strain alleviating membrane (SAM) – A sprayed seal in which the bituminous binder is formulated to reduce
a liquid, in response to an applied stress.
reflective cracking, usually by the incorporation of polymer. Used to waterproof an underlying cracked pavement surface.
viscometer – An instrument for measuring the viscosity of a material.
strain alleviating membrane interlayer (SAMI) – Similar
viscosity – The property of a fluid whereby, through internal friction, it resists movement and expressed as the stress divided by the strain rate.
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.
voids – See air voids. 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.
wearing course – The surface layer of a pavement that is in direct contact with traffic.
basics BP Bitumen Australia
For advice on which product to use to meet your specific job requirements, please contact us:
On the web: www.BPBitumen.com.au By e-mail:
[email protected] Technical Helpline: 1800 24 88 66 Or contact the BP Bitumen sales manager in your region.
BP Bitumen Offices Head Office BP Bitumen Australia 55 Toll Drive, Altona North, Victoria PO Box 495, Altona North VIC 3025 Telephone: (03) 8368 8700 Facsimile: (03) 8368 8701
Queensland / New South Wales / Northern Territory BP Whinstanes Building B, 701 Kingsford Smith Drive Hamilton, Queensland 4007 PO Box 718, Hamilton QLD 4007 Telephone: (07) 3364 7093 Facsimile: (07) 3364 7102
Tasmania BP Bitumen Selfs Point Selfs Point Road, Newtown, Tasmania PO Box 282, Moonah TAS 7009 Telephone: (03) 6278 1310 Facsimile: (03) 6278 2205
Victoria / South Australia BP Bitumen Altona 55 Toll Drive, Altona North, Victoria PO Box 495, Altona North VIC 3025 Telephone: (03) 8368 8700 Facsimile: (03) 8368 8702
Western Australia BP Bitumen Kwinana Mason Road, Kwinana, Western Australia PO Box 2131, Rockingham WA 6167 Telephone: (08) 9419 9712 Facsimile: (08) 9419 9820
The information provided in this Guide is of a general nature and should only be used as a guide. Please contact BP Bitumen staff to ensure you have access to the most current information and for advice relating to any particular circumstances. BP Australia Pty Ltd (BP) makes no warranty as to the completeness or accuracy of the information provided and, to the fullest extent permitted by applicable law, BP 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. BP, Olexobit, Multibit, Aquabit and the Helios Design are registered trade marks of BP p.l.c. and licensed to BP Australia Pty Ltd for use in Australia. © BP Australia Pty Ltd ABN 53 004 085 616, Melbourne Central, 360 Elizabeth Street, Melbourne 3000, Australia. Printed October 2007. wam9774.
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