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Definition of Bitumen :
is a category of organic liquids that are highly viscous, black, sticky and wholly soluble in carbon disulfide. Asphalt and tar are the most common forms of bitumen. bitumen has made of oil (petroleum) by a special method called distillation.
In generic term referring to flammable, brown or black mixtures of tar like hydrocarbons, derived naturally or by distillation from petroleum. It can be in the form of a viscous oil to a brittle solid, including asphalt, tars, and natural mineral waxes. Substances containing bitumen are called bituminous, e.g., bituminous coal, tar, or pitch.
Bitumen does occur naturally, but for all intents and purposes it is petroleum on which the world relies for its supplies of bitumen today. The bitumen content of crude can vary between 15% and 80%, but the more normal range is 25% to 40%. In fact the three broad classifications for crude oils are:
bitumen based
paraffin based
bitumen and paraffin based
Depending on the type of crude, bitumen is present either in the form of colloidal dispersed particles 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 being dispersed and relatively few in number, the particles become closer to one another and the size of the particles increases. At the point when the distillation process is usually stopped, the petroleum bitumen is a colloidal dispersion of black solids (hydrocarbons), known as asphalt ness, in a dispersion medium, which is an oily brown yellow liquid known as malthene fraction.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 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.
However it may be found as an asphaltite, a natural bitumen without impurities that varies in the extent to which it is soluble in carbon disulphide. Natural bitumen occurs, as does petroleum, 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. 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.
Bitumen's main property is that of a very 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 do its job for 20 years or more. Bitumen is insoluble in water but is soluble in numerous organic solvents. As it is highly waterproof, it can act as an effective sealant. It also resists action by most acids, alkalis and salts. It does not contaminate water so it can be used to line watercourses.
There are five major classifications of petroleum bitumen produced by the refining and manufacturing process:
Paving grade bitumen (or asphalt cement in American usage): is refined and blended to meet road engineering and industrial specifications that take into account different climatic conditions. As a product it is the most widely used bitumen.
Cutback bitumen: consist basically of bitumen that has been diluted in order to make it more fluid for application, mainly in road making. Their fluidity depends on the degree of hardness of the bitumen base and the proportion of diluents (or flux) to bitumen. They are classified according to the time it takes them to become solid, as rapid curing (RC), medium curing (MC) or slow curing (SC) cutbacks.
bitumen emulsions: the basic bitumen has also been diluted (watery) in order to facilitate application. Hot bitumen, water and emulsifier are processed in a high-speed colloid mill that disperses the bitumen in the water in the form of globules that are normally in the 5-10 micrometer size range but may be even smaller. Bitumen emulsions have a low viscosity and can be workable at ambient temperatures, which makes them ideal for use in road building. This 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.
Industrial bitumen: (or oxidized bitumen) are made by blowing air through hot paving grade bitumen. The result is a product that softens at a higher temperature than that at which paving grade bitumen softens. It also has more rubber like properties and its viscosity is much less affected by changes in temperature than is the case with paving grade bitumen.
Modified bitumen: Are formulated with additives to improve their service performance by changing such properties as their durability, resistance to ageing, elasticity and/or plasticity. As well as natural rubbers, polymers such as styrene butadiene styrene (SBS), thermoplastic rubbers and ethylene vinyl acetate (EVA) are commonly used to modify bitumen and some companies, including BP, have their own proprietary technology using special polymers or polymer blends.
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It is the most part of construction of Highways, Roads and waterproof structures. Most usage of this product is For making pavement mixtures. it founds in deferent types and for various purposes.
Generally there are two kind of Bitumen is Used, Soft Bitumen and Rigid Bitumen .and also divided by several types in according their physical properties like softening ,elasticity and etc. which generally called Normal Bitumen And Modified Bitumen.
There are several tests Related to Bitumen and its products, which we will describe here most of important test which are important for High ways construction .
