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 60oC) 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
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.
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.
|Absolute Viscosity, 60oC, poises, min||800||1600||2400||3200|
|Kinematic Viscosity, 135oC, CST, min||250||300||350||400|
|Flash point, C, min||220||220||220||220|
|Solubility in trichloroethylene, %, min||99.0||99.0||99.0||99.0|
|Penetration at 25oC||80-100||60-80||50-70||40-60|
|Softening point, C, min||40||50||40||50|
|Tests on residue from thin film over test / RTFOT:|
|i. Viscosity ratio at 60oC, max||4.0||4.0||4.0||4.0|
|ii. Ductility at 25oC, cm, min, after thin film over test||75||50||40||25|
(IS:73-2006) Grade 60/70 and 30/40. Straight grade used in construction and maintenance of roads, airfields and allied constructions, manufacturing of bitumen Emulsions.
Bitumen is the end product in the crude distillation process. This raw bitumen is called Straight grade bitumen and has penetration values of 200-300. The straight grade bitumen obtained from the refineries is processed in our highly modernized plant through the exothermic reaction, to the relevant time limit to produce the desired Paving Grades as per the specifications.
Viscosity Grade bitumen is designed to take care of lowest temperature(responsible for cracking) and maximum temperature(responsible for rutting).
- VG system is based on fundamental engineering parameter (not empirical)
- Viscosity is measured at 60degree C and 135degree C, which takes care of both low and high-temperature susceptibility of the binder, which is not possible with penetration value at 25degreeC. Hence pavement engineers, contractors/consultants can have a better understanding of the binder’s performance in the field.
- Any two same viscosity grade bitumens would give similar rutting performance in the field.
- Greater ease of handling to customers as Viscosity Value at two different temperatures(60degreeC and 135degree C) is available, which would enable users to measure accurate mixing and compaction temperatures.
- Minimum specified Kinematic Viscosity value at 135degree C helps to minimize the potential of tender mixes during construction.
- Viscosity graded bitumens are suitable for a wide range of temperature: 25degreeC for raveling/fatigue cracking. 60degreeC for rutting and 135degreeC for construction(mixing and compaction).
- IS 73-2006 has only 7 tests to evaluate a sample compared to 14 tests in penetration grade system. This reduces time and cost of testing without sacrificing its quality.
Straight Grade Bitumen is processed in our plant for a longer period. By this process, Bitumen becomes sludge/moisture free and softening/penetration values are improvised to a great extent. This is called Blown Bitumen and the same has the wide range of industrial applications. These Grades are further distinguished depending upon their softening points and penetration values.
Grade 85/25, 90/15, 115/15.
Industrial grade bitumen is used in waterproofing, damp proofing, acid/alkali resistant, subflooring, canal lining, road construction, joint fillers, lamination, battery sealing, a base for cable joining compound and manufacturing of paints, printing inks, explosives etc.
Ambient temperatures. In road making, bitumen products are typically applied with mineral aggregate. The strong adhesion that occurs between the bitumen and mineral aggregate enables the bitumen to act as a binder, with the mineral aggregate providing mechanical strength for the road.
Bitumen is difficult to work with, at ambient temperatures, since it is a highly viscous material under these conditions. it can, however, be transformed into a workable state by blending with petroleum solvents or by emulsification with a surfactant in water to form a bitumen emulsion.
Emulsified bitumen acts as a key tool in road maintenance and construction technology as it combines amazing versatility while offering multiple comparative advantages.