Bitumen is a dense substance that exists in a range between liquid and semi-solid states. It is characterized by its dark brown or black color and is primarily composed of asphaltene resin and other petroleum derivatives. Different compositions result in varying properties of bitumen.
The main application of bitumen (around 70%) is in road construction, where it acts as an adhesive or binder when combined with aggregate particles to form asphalt concrete. It is also widely used in bituminous waterproofing products, such as roofing felt and flat roof sealing.
Exploring Asphalt Varieties and Their Uses
A plethora of asphalt types, each with unique properties, is produced from varying crude oils, thereby necessitating a robust classification system. Refineries administer a series of standardized tests that measure viscosity, penetrative abilities, performance, and consistency to categorize asphalt according to its unique characteristics. This rigorous examination process differentiates asphalt into several grades, primarily penetration grades and viscosity grades.
Additional categories of asphalt, including diluted, oxidized, and emulsified asphalt, are sorted based on their manufacturing process.
• Gilsonite (Natural Asphalt)
Gilsonite, a variant of natural asphalt, is recognized by its glossy, smooth, and solid facade. Varieties of Gilsonite can be distinguished by their ash content and their solubility in organic solvents. This rigid and brittle substance is mostly used in powdered form, with a composition closely paralleling that of refinery-produced asphalt. Mixed with refined asphalt, Gilsonite is occasionally employed in road construction due to its superior resistance to water penetration. However, it has relatively low penetrative properties and is prone to deformation.
Applications of Gilsonite:
- Printing industry
- Coating industry
- Drilling fluids and cement
- Asphalt and highway construction
- Foundry sand additive
- Chemical products
- Asphalt quality enhancement
• Penetration Grade Asphalt
Penetration grade asphalt, the go-to type for road construction, is categorized based on its penetrative capacity using a penetrometer during a bitumen penetration test. The softer the asphalt—evidenced by deeper needle penetration—the more suitable it is for colder climates. The 60/70 grade of penetration grade asphalt is predominantly employed for road construction and building waterproofing, followed by the 80/100 grade. Utilizing this asphalt variety necessitates considering regional average temperature and traffic volume.
• Viscosity Grade Asphalt
The classification of viscosity grade asphalt is based on its viscosity post-refinery production. This categorization method is relatively more modern than penetration grading. India is the principal consumer of this asphalt type, which comes in four distinct grades: VG 10, VG 20, VG 30, and VG 40, each catering to specific applications. The shift towards viscosity grading arises from the asphalt viscosity alterations at high temperatures.
Here are some benefits of VG asphalt compared to penetration grades:
The viscosity grading methodology is designed to increase the reliability of asphalt performance at elevated temperatures. A specific penetration grade asphalt might exhibit inconsistent behavior at a particular temperature, while VG asphalt remains stable.
VG asphalt is preferred for anticipating asphalt performance during peak heat periods and under standard weather conditions. As viscosity testing evaluates asphalt properties at three distinct temperatures (25° C, 60° C, and 135° C), VG asphalt grades ensure an optimized application process.
• Bitumen Emulsion
Bitumen emulsion, a distinct type of bitumen, is concocted through the chemical amalgamation of bitumen and water. This innovative approach was designed to circumvent the environmental repercussions associated with cutback bitumen, with water serving as an effective, echo-friendly substitute for organic solvents, enabling bitumen dilution for specific uses. Bitumen emulsions prove ideal for road upkeep and the rejuvenation of dilapidated roads. In contemporary bitumen industries, this emulsion is frequently deployed in tack coats, chip seals, slurry seals, and micro surfacing.
• Cutback Bitumen
Cutback bitumen caters to industries demanding low-viscosity bitumen, also providing a solution in scenarios where preheating bitumen to produce asphalt is unachievable. This variant of bitumen is fabricated by blending penetration bitumen with specified quantities of organic solvents, such as gasoline, naphtha, diesel oil, and furnace oil. The resulting cutback bitumen, suitable for colder climates, evaporates its solvents upon application. However, this type of bitumen harbors a significant concern—its potential environmental harm. The volatility of its solvents poses considerable risks to nature, human health, and our environment.
• Oxidized Bitumen
Oxidized bitumen, derived from injecting hot air into penetration bitumen within refineries, exhibits chemical stability, superior resilience, and resistance to water—properties ideal for insulation. Compared to pure bitumen, oxidized bitumen has a lower penetration degree and a higher softening point. Its applications extend to waterproofing in dam construction, diverse construction projects, road construction in tandem with other bitumen types, and coating pipelines to prevent corrosion in industries, especially oil, and gas.
