Bitumen

Bitumen History

Bitumen is the oldest known engineering material and has been used from the earliest times as an adhesive, sealant and waterproofing agent. As long ago as 6000BC the thriving ship-building industry in Sumeria used naturally occurring bitumen, found in surface seepage in the area.

In the Indus Valley, now in Pakistan, there is a particularly well-preserved water tank which dates back to around 3,000 BC. The stone blocks in the tank's walls are bonded with natural bitumen and there is a vertical bituminous core in the centre of the wall ­ this same principle is used today in modern dam design. It is believed that Nebuchadnezzar was one of the early exponents of bitumen as there is evidence that he used the material for waterproofing the masonry in his palace and as grout for stone roads.

Bitumen's versatility as a construction material is unparalleled. Having been used as an adhesive, sealant and waterproofing agent for over 8,000 years, its uses now include: the construction and maintenance of roads, airfields and all areas where asphalt is used; roofing; damp proofing; dam, reservoir and pool linings; soundproofing, pipe coatings, paints, and many others.

There appears to have been little development in materials used until the 19th century when the refining of bitumen from crude petroleum oils began. The vast majority of bitumen used by today's construction industry is refined bitumen, derived from crude oil. It is a sophisticated product available in many forms and grades developed by the bitumen industry for specific uses.

The process of refining bitumen was pioneered in the early 1900s in the United States, giving rise to a myriad of contemporary industrial applications.

Bitumen Specifications

Bitumen is a thermoplastic material and its stiffness is dependent on temperature. The temperature-vs-stiffness relationship of bitumen is dependent on the source of crude oil and the method of refining.

The Bureau of Indian Standards (BIS) introduced paving grade bitumen specifications (IS: 73- 1950) for the first time in the year 1950 and classified it on penetration. The specifications were revised in the years 1962 and 1992. To improve the quality of Bitumen, BIS revised IS-73-1992 specifications based on Viscosity (Viscosity at 60o C) in July 2006. As per these specifications, there are four grades VG-10, VG-20, VG-30 & VG-40. A few qualification tests like specific gravity, water content, ductility, loss on heating & Farass breaking point were removed from IS: 73-1992 specifications as these tests do not have any relationship either with the quality or performance of the product. 

IndianOil commenced marketing of Bitumen as per Viscosity Grade specifications conforming to IS: 73-1992 from all its refineries from Aug 2009. Therefore, the Penetration grades have been replaced by Viscosity grade Bitumen.

According to viscosity (degree of fluidity) grading, higher the grade, stiffer the Bitumen. Tests are conducted at 60o C and 135o C, which represent the temperature of road surface during summer (hot climate, similar to northern parts of India) and mixing temperature respectively. The penetration at 25o C, which is annual average pavement temperature, is also retained.

Different Grades of Bitumen marketed by Indian Oil :

VG-10 BITUMEN: VG-10 is widely used in spraying applications such as surface-dressing and paving in very cold climate in lieu of old 80/100 Penetration grade. It is also used to manufacture Bitumen Emulsion and Modified Bitumen products.

VG-20 BITUMEN: VG-20 is used for paving in cold climate & high altitude regions

VG-30 BITUMEN: VG-30 is primarily used to construct extra heavy duty Bitumen pavements that need to endure substantial traffic loads. It can be used in lieu of 60/70 Penetration grade.

VG-40 BITUMEN: VG-40 is used in highly stressed areas such as intersections, near toll booths and truck parking lots in lieu of old 30/40 Penetration grade. Due to its higher viscosity, stiffer Bitumen mixes can be produced to improve resistance to shoving and other problems associated with higher temperature and heavy traffic loads.