Expert Tips
HISTORY OF BITUMEN
Throughout history, fossil-based bitumen has been used since ancient times as a medicine for diseases and as an incendiary substance in wars. With the development of structures used by mankind, clay, lime, tar (vegetable), and fossil-based bitumen have been used in history, especially as waterproofing materials. In those days, bitumen filled into the joints between stones was mixed with mineral powders and applied in layers, and sometimes plant fibers and stalks were added to this mixture.
Asphalt, which is a mixture of mineral aggregates and bitumen, has been perceived as the same term as bitumen in some countries. It has been found that asphalt, which is a component of fossil-based bitumen and a naturally calcified rock, was first used in road and wall construction in Mesopotamia and the Indus Valley between 3200–540 BC. Asphalt was used extensively for waterproofing. The material in the 16th century was cast asphalt, which could provide continuous waterproofing. Asphalt, which is a component of fossil-based bitumen and a naturally calcified rock, was well known especially in Southern Italy and France. With the discovery of new resources in the mid-18th century, it began to be widely used in Germany and the Netherlands as well.
It has been determined that asphalt was used in France in the early 1800s for coating bridge and sidewalk surfaces, and it is known that the city of Philadelphia in the United States imported some asphalt for sidewalk construction in 1838. In 1870, the first asphalt road pavement was made in New Jersey by the Belgian chemist E.J. de Smadt. In Washington, road pavement was carried out with imported asphalt in 1876.
In the late 18th century, the use of asphalt on roofs did not give positive results, so different materials were tried. A German scientist named Margerger insulated a wooden roof near Nuremberg - Germany by priming it repeatedly with coal tar using a new method. Tar obtained from coal was first discovered in England towards the end of the 17th century; however, the availability of tar increased considerably with the Industrial Revolution in the 19th century.
With the development of the modern chemical industry, the use of tar and pitch has become increasingly widespread. Tar, which is poured in layers on terrace roofs with tar paper in between, is obtained by distilling coal. Until recently, tar and pitch were thought to be petroleum-based and were therefore considered to have the same properties as bitumen. Even today, both can be confused because they are insoluble in water, have excellent adhesion, are used in the construction sector, and are black in color. Tar, one of these materials with different origins and chemical properties but the same usage areas, has gradually been replaced by bitumen because it is harmful to health.
Bitumen is the heavy petroleum component remaining after volatile and light fuels are refined from crude oil. Bitumen obtained from distilled petroleum was mostly used as an adhesive in road construction. Because it melts at 50 °C and breaks at 0 °C, it prevented its use on building roofs. In a method tried later, high-temperature air was blown into molten bitumen. This method ensured that the structure of bitumen, which was modified with oxygen, achieved better thermal stability. With the temperature range of this type, known as “Oxidized” bitumen, being between -5°C and +70°C, the process of using bitumen for waterproofing purposes on building roofs began. Oxidized bitumen is the raw form of bituminous membranes we use on roofs.
In these periods, waterproofing was carried out by heating oxidized bitumen, which was made fluid by heating it in special containers that could reach temperatures of up to 200–220 °C at the application site, and applying it between carrier cardboard layers in layers. Hot bitumen, which is poured directly onto the area to be applied, is spread on the surface with wide brushes. After this process, bituminous cardboard rolls are laid, and these processes are repeated several times to carry out 3–4 layer applications with bituminous cardboard. In the English method, the application was carried out by pouring hot bitumen just in front of the bituminous cardboard being laid. As a result, a layered and continuous waterproofing membrane with a total thickness of 8–10 mm emerges.