What is Bitumen?
Bitumen is a mixture of dense, sticky, viscous organic liquids composed mainly of polycyclic aromatic hydrocarbons and obtained naturally by the distillation of crude oil. It is a complex colloidal system whose chemical properties depend on the properties of the crude oil from which it is obtained. Bitumen is a black or dark (viscous, non-volatile liquid , semi-solid or solid), amorphous, cementitious material that can be found in various forms as hard, slightly friable bitumen in rock asphalt and as softer, more viscous material found in tar sands and asphalt ‘lakes’. Bitumen derived from oil, called petroleum bitumen commonly referred to as bitumen or asphalt.
Pure bitumen is a colloidal dispersion of microscopic asphalt particles (dispersion phase). It is a semi-solid hydrocarbon product formed by the removal of the lighter fractions (such as liquefied petroleum gas, gasoline, and diesel) from heavy crude oil during the refining process. As such, it is correctly referred to as refined bitumen.
The chemical composition of bitumen is a mixture of various hydrocarbons with oxygen, Sulphur and nitrogen molecules. The hydrocarbons contained in bitumen are mainly fused naphthenic and aromatic rings with a small number of paraffin side chains. The mass fraction of hydrocarbons is 75-85%, hydrogen 9-10%, oxygen 2-8%, Sulphur 5-7% and nitrogen 0.1-0.5%.
In North America, however, the liquid binder is referred to as “Asphalt cement” or “asphalt”. In other countries, In Europe, for instance “bitumen” means the liquid binder and “asphalt” is the name given to a mixture of small stones, sand, filler, and bitumen used as a road surface.
In general, the term “bituminous materials” is used to refer to substances in which bitumen is contained or from which it can be extracted. Bituminous substances consist mainly of bitumen and tar.
Why is Bitumen important?
Without bitumen, our world would look very different. Our cities and our homes would be very different, our lives would be less mobile and less connected. A significant component of the asphalt we use to build roads, bitumen holds our roads together and connects cities and countries across vast distances. It forms the backbone for personal and business travel, tourism and logistics.
Bitumen is an unsung hero of our modern world. The substance is responsible for waterproofing, sealing and insulating various materials in a variety of industries. Asphalt pavements with bitumen today make very smooth roads for light and heavy vehicles and high quality runways for landing and taking off aircraft and even good infrastructure for railways. Insulation of houses and industrial functions such as protecting coating of oil and gas pipes and power lines withstand the coating of bitumen and are waterproof. In addition, bitumen is used in road construction as a strong binder. The world demand for bitumen today is more than 100 million tons per year, which is approximately 700 million barrels of bitumen consumed annually.
Bitumen not only reduces the cost of road construction, but also reduces the need for maintenance and extends the life of roads around the world.
There are different types and grades of bitumen. Depending on the raw material (natural or refined), bitumen has different characteristics and properties. This leads to classification of bitumen into different grades with different applications.