What does VG stand for in bitumen grading?

VG stands for Viscosity Grade. It classifies bitumen based on its absolute viscosity measured at 60°C.

What is the modern equivalent of the old 60/70 and 80/100 penetration grades?

VG-30 generally replaces the old 60/70 penetration grade, while VG-10 replaces the old 80/100 penetration grade.

Which bitumen grade should be used for heavy traffic conditions?

VG-40 should be used for heavy traffic loads and in high-temperature regions to resist permanent deformation (rutting).

What is the minimum softening point for VG-30 bitumen?

The minimum softening point for VG-30 is 47°C, as specified in Table 1.

IS 73

: 2013

Paving Bitumen - Specification

CurrentEssentialSpecificationTransportation · Roads and Pavement

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This standard specifies the physical and chemical requirements for paving bitumen used in highway construction and flexible pavements. The standard famously transitioned the Indian industry from penetration-based grading (e.g., 60/70, 80/100) to Viscosity Grading (VG-10, VG-20, VG-30, VG-40), which provides a more reliable indicator of field performance, particularly concerning rutting at high temperatures.

Specifies requirements for various grades of paving bitumen used in road construction and other civil engineering applications.

Quick Reference Values

Absolute Viscosity at 60°C for VG-30Min 2400 Poise

Absolute Viscosity at 60°C for VG-40Min 3200 Poise

Kinematic Viscosity at 135°C for VG-30Min 350 cSt

Minimum Penetration at 25°C for VG-3045 (0.1 mm)

Minimum Penetration at 25°C for VG-4035 (0.1 mm)

Minimum Softening Point for VG-3047°C

Minimum Softening Point for VG-4050°C

Minimum Flash Point (Cleveland Open Cup) for all VG grades220°C

Practical Notes

VG-30 is typically used for general paving in most parts of India, serving as the equivalent to the older 60/70 penetration grade.

VG-40 is highly recommended for highly stressed areas like intersections, toll plazas, and heavy commercial vehicle routes to prevent rutting.

Viscosity tests are conducted at two temperatures: 60°C (Absolute Viscosity) to simulate maximum road temperatures, and 135°C (Kinematic Viscosity) to simulate mixing/compaction temperatures.