Types and Properties of Bituminous Materials
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Importance and background of Bituminous Material:
Bitumen is an essential component of any pavement and is used widely throughout the world. It can be termed as the building block of the pavements without which all the pavement materials would behave independently and thus will be deemed useless. Almost ninety percent of bitumen is used in road construction. It is usually available in dark colors ranging from brown to black. The main purpose of bitumen in flexible pavements is to strongly bind and hold the other pavement components together and provide a smooth and leveled surface for the moving vehicles. Bitumen is a naturally occurring material and is found in large quantities in the solid or semi solid forms of petroleum. It is also manufactured artificially in vast amounts globally.
Bitumen mixed with some other materials has always been used as a sealant and adhesive material over the ages. It was also widely used in the water proofing of boats and ships as it is insoluble in water. Highest applications of bitumen are found in the construction filed for the construction of roads, airports etc, in the hydraulic field for the construction of water tanks, dams, bridges etc, is also used in battery making, tyre making and for the thermal and acoustic insulation purposes.
Properties of Bituminous Materials:
The high demand of bituminous materials is owing to the number of their first-rate advantageous properties listed below:
2. Water proof: Bitumen is insoluble in water and can serve as an effective sealant
3. Strong: Though the coarse aggregates are the main load bearing component in a pavement, bitumen or asphalt also play a vital role in distributing the traffic loads to the layers beneath.
4. Durable: Bitumen lives upto twenty years if maintained properly throughout the pavement life.
5. Versatile: Bitumen is a relatively easy to use material because of its thermoplastic property. It can be spread easily along the underlying pavement layers as it liquefies when heated making the job easier and hardens in a solid mass when cooled.
6. Economical: It is available in cheaper rates almost all over the world
Types of Bituminous Materials:
Depending upon the temperature and other factors various types of bitumen are found and used throughout the world.
Cut-back bitumens are those which are prepared with the addition of a volatile to reduce the thickness of the binder.
Fluxed bitumens are those bitumen which are prepared by the addition of relatively non volatile oils to reduce the viscosity of the binder.
Modified bituminous binder are those whose properties such as cohesive strength, adhesive property, elasticity or viscosity have been modified by the use of one or combined chemical agents.
Asphalt is a mixture of aggregates both fine (sand and filler) and coarse (stone) and a bituminous binder. It typically contains approximately 4-7% of bitumen. Asphalt is primarily used in road construction and its properties depend upon the type, size and amount of aggregate used in the mixture, all of which can be adjusted to provide the required properties for the desired application.
Owing to their high thermoplastic properties, bitumen is always recommended to be used wearing all protective gadgets. Even a small drop of highly heated bitumen can cause severe burns to exposed body parts. Therefore high care is needed in the handling of any type of bitumen to avoid any mishaps during site work.