When we talk about flexible pavement construction, one thing that always comes into focus is bitumen. It works as a binder, glue, and waterproofing material for every layer from BM, DBM, BC to SDBC. But today, different types of bitumen grades are available and each grade has its own purpose. If you choose the wrong grade, the road will fail early with rutting, cracking, or bleeding. So let’s understand bitumen grades in the simplest and most practical way.
What is Bitumen Grade?
Bitumen grade means the classification of bitumen based on viscosity, penetration, softening point, and performance under temperature and traffic load. In simple language—
grade tells us how hard or soft the bitumen is and how it will behave on the road.
1. VG Grade Bitumen (Viscosity Grade)
This is the most commonly used system in India. It replaced the earlier “penetration grade”.
Types of VG Grades
VG-10
Used in cold climate areas, low traffic roads, thin bituminous layers.
Soft bitumen, flows easily during mixing.
VG-20
Used in medium rainfall, moderate temperature regions. Good for rural and semi-urban roads.
VG-30
Most widely used on highways in India. Suitable for dense traffic and hot climate.
Used for DBM, BC, BM works.
VG-40
Used for very heavy traffic, extremely hot climate, expressways, and industrial areas.
More resistant to rutting.
Simple Selection Tip
Hot climate + heavy traffic = higher VG grade
Cold climate + low traffic = lower VG grade
2. Penetration Grade Bitumen (OLD System)
Although India mainly uses VG grade, some old DPRs still mention penetration grade like 60/70 or 80/100.
80/100 = softer bitumen
60/70 = stiffer, mostly used earlier for highways
Pen value shows how deep the needle penetrates into bitumen. Lower penetration = harder bitumen.
3. PMB (Polymer Modified Bitumen)
PMB is bitumen mixed with polymers to improve performance.
Where it is used?
Heavy-load roads
Toll plazas
Flyovers
Areas with high temperature variation
Benefits
Higher rutting resistance
Less cracking
Longer life of road
Common types: PMB-40, PMB-70
4. CRMB (Crumb Rubber Modified Bitumen)
Waste rubber (like old tyres) is mixed with bitumen.
Benefits
Better elasticity
Improved resistance against deformation
Good for high-temperature zones
Also environment-friendly.
How Bitumen Grade Impacts Road Quality?
If grade is too soft → road bleeds, waves form
If grade is too hard → road cracks early
Correct grade → smooth surface, long life, strong binding
This is why choosing VG-30 in hot regions and VG-40 in expressways has become standard practice.
Quick Comparison Table
Bitumen Grade Climate Traffic Use
VG-10 Cold Low Primes, thin layers
VG-20 Moderate Medium BM, rural roads
VG-30 Hot High DBM, BC for highways
VG-40 Very Hot Very Heavy Expressways, industrial roads
PMB All Heavy Toll, bridges
CRMB Hot High Heavy-load traffic
Conclusion
Bitumen grade selection is one of the most important decisions in highway construction. The correct grade improves strength, durability, and safety of the pavement. In simple words—right grade = long-lasting road. Most of the highway projects today prefer VG-30 or VG-40 depending on traffic and temperature.
