Also referred to as asphalt in North America, bitumen has two forms, crude or refined. Crude bitumen is usually found to be naturally occurring in various organic liquids and refined bitumen is the residue yielded in the distillation process of coal or petroleum. The substance, which can be a highly viscous liquid or semi-solid, is sticky, brown-black in color and is similar to tar. It was the first oil product that was used by humans due to its cohesive and adhesive properties. Today, it is mostly used with other substances such as tar in the paving of roads. It is used as the glue or binder, having been mixed with aggregate particles to create asphalt concrete. Other than being used in the construction of roads, bitumen is also used for bituminous waterproofing of products, for example roofs. Both asphalt and bitumen are terms being used interchangeably to describe both natural and manufactured forms of the substance.
In its natural form, crude bitumen is usually in solid or semi-solid, consisting mostly of hydrocarbons. Organisms that lived on the planet get buried under the soil, and overtime, become buried deep inside the Earth’s crust. Here, the decomposition of these organisms is affected by the intense pressure and heat inside the Earth’s crust, which leads to the formation of bitumen. Such deposits of bitumen are present all over the world, with the largest deposits being located in Canada and Venezuela. With its presence in various Neanderthal tools, the use of bitumen can be traced back several thousand of years, with human uses of the material dating as far back to 5000BC.
Although bitumen is commonly used together with tar today, it can sometimes be mistaken to be tar. Tar has a similar color and is a thermoplastic material produced by the destructive distillation of coal. The substance is obtained from other components in crude oil such as gasoline and diesel through the process of fractional distillation. This process separates the several different substances that make up crude oil into their separate forms. To further achieve a harder, more viscous and thicker form of the substance, the separated bitumen substance can then be further treated in a de-asphalting unit. The heavier fractions of crude oil are used in this process, having them be treated with oxygen through the process of ‘blowing’. Once separated, the substance is usually stored and transported at temperatures around 150°C and sometimes even diesel oil or kerosene are added to it, in order for it to sustain its liquidity when being delivered over long distances. Once it has reached its destination, the added substances can be easily separated out of the mixture. This mixture of the substances is referred to as bitumen feedstock. Natural deposits of bitumen are too low around the world. Therefore, bitumen is mostly derived from fractional distillation process of crude oil to meet the demands of the world. Various grades of bitumen can be attained from the residue that is achieved from the process. Also, with advancements in technology, the substance can now ever be attained from non-petroleum substances such as corn, molasses starches and rice.
The use of bitumen does not only extend to construction of roads or as a waterproofing agent in roofs, but its use varies according to geographical and societal contexts. Complex tools that require a binding element make use of bitumen in their construction. It is also believed that bitumen served as a preservative in the mummification process in Ancient Egypt. Bitumen is a very essential material in today’s industry, fulfilling several roles in the different industries that it is used in.