Road Construction in India: The Role of Bitumen Grades

Road Construction in India increasingly depends on selecting the right bitumen grade for climate, traffic loading, and performance standards. From national highways to rural roads, choosing between VG, PMB, and other modified binders directly affects pavement life, maintenance costs, safety, and even lifecycle carbon footprint.

India’s Bituminous Road Boom: Why Binder Choice Matters

India now has the world’s largest road network, exceeding 6.6 million km and carrying over 70% of freight and about 85% of passenger traffic. National Highways alone have expanded by about 60% since 2014, reaching roughly 146,000 km.

Yet performance and safety remain challenges:

• Annual road crash fatalities have crossed 1.77 lakh in 2024.

• Overloaded trucks, extreme summers, heavy monsoons, and rapid construction cycles stress flexible pavements.

• Poor grade selection and construction control still cause premature rutting, bleeding, and cracking.

Because of this, MoRTH and IRC design standards now treat bitumen selection as a design decision, not a commodity purchase. IRC:37-2018 links layer thickness, traffic, and climate to performance criteria such as rutting and fatigue. Recent MoRTH circulars also tie the use of polymer modified bitumen (PMB) and crumb rubber modified bitumen (CRMB) to BIS service-condition tables.

In practice, the “right” bitumen grade should:

• Match regional temperature and rainfall

• Match design traffic (million standard axles and commercial vehicles per day)

• Meet IRC/MoRTH specifications for the chosen layer

• Stay workable for site equipment and local contractor capability

• Improve lifecycle cost, not just initial rate per tonne

Bitumen Grades that Power Road Construction in India

Conventional viscosity grades (VG-10, VG-20, VG-30, VG-40)

India largely shifted from penetration grades to viscosity grades under IS 73, because viscosity-based control better captures performance in hot climates. In practice:

• VG-10 – Spraying, surface dressing, and bitumen emulsion feedstock; colder regions and low-traffic roads.

• VG-20 – Colder/high-altitude regions (Himalayan states), where flexibility at low temperatures matters.

• VG-30 – The workhorse for dense bituminous macadam (DBM) and bituminous concrete (BC) on normal highways and urban roads in moderate climates.

• VG-40 – Stiffer binder for heavy truck corridors, expressways, and very hot regions to improve rutting resistance.

Design catalogues and many NHAI contracts now recommend VG-30 for typical highways and VG-40 for high-traffic or high-temperature sections, subject to detailed mix design.

Modified binders: PMB, CRMB and high-performance mixes

Modified binders aim to extend life and resist extreme loading:

• PMB (Polymer Modified Bitumen) adds elastomers or plastomers to improve elasticity and rutting resistance.

• CRMB (Crumb Rubber Modified Bitumen) uses tyre rubber to improve elasticity, fatigue life, and temperature susceptibility.

• SMA binders (Stone Matrix Asphalt) typically use PMB to maintain stone-on-stone skeleton and prevent drain-down.

IRC:SP:53 and related MoRTH circulars generally recommend PMB for heavy-duty pavements with >1500 commercial vehicles per day, especially expressways and urban arterials with frequent braking and wheel wander. MoRTH’s 2024 bitumen circular explicitly links PMB grade selection to BIS 15462:2019, which defines service conditions by climate and traffic categories.

Emulsions and speciality binders for rural and maintenance works

For PMGSY and other rural programmes, bitumen emulsion and cold mixes are increasingly common because they:

• Allow work with less heating and simpler plants

• Reduce fumes and energy consumption

• Enable patching and thin surfacing in remote areas

Emulsions (SS, MS, RS grades) are used for tack coats, prime coats, slurry seals, and micro-surfacing. Cold mixes using emulsions or foamed bitumen provide viable solutions for low- to medium-traffic rural roads, avoiding heavy hot-mix plant logistics.

Table 1 – Common Bitumen Options in India and Where They’re Used

How to Select the Right Bitumen Grade – A Step-by-Step Method

You can treat binder selection like a mini design problem rather than a quick line item. A practical workflow:

1. Define project context

   • Road category (NH, SH, MDR, village road)

   • Design life and lane configuration

   • Construction window (peak summer, monsoon shoulder season, winter)

2. Quantify traffic

   • Current commercial vehicles per day and projected growth

   • Convert to design traffic in msa as per IRC:37.

3. Assess climate and pavement temperature

   • Maximum and minimum air temperatures

   • Rainfall, drainage conditions, and waterlogging risk

   • Urban heat-island effects for dense cities

4. Pre-select binder family

   • Low msa + moderate climate → VG-30 or emulsion-based surfacing

   • High msa (≥20) or truck-dominated corridors → VG-40 or appropriate PMB grade

   • Very cold, low-traffic hill roads → VG-10/VG-20 with high flexibility

5. Check layer type and thickness

   • DBM vs BC vs SMA vs mastic asphalt

   • Thin layers (<40 mm) on heavy traffic often require SMA with PMB or a very stable mix.

6. Validate with mix design and lab testing

   • Marshall / Superpave stability and flow

   • Wheel-tracking or rutting tests for critical stretches

   • Fatigue tests for long-life pavements and perpetual pavement designs

7. Confirm compliance with MoRTH + IRC + BIS

   • Verify that binder type and viscosity/penetration/emulsion grade match the latest MoRTH specifications and relevant IRC special publications.

8. Plan field controls

   • Storage temperature, mixing temperature, and compaction temperature windows

   • Batch-type hot-mix plants are now mandated on NH works for quality control

Table 2 – Simplified Bitumen Grade Selection Matrix

Micro Tutorial: Two Realistic Scenarios

1) Four-lane freight corridor in Rajasthan

• Climate: Very hot summers, modest rainfall

• Traffic: 30 msa, high proportion of multi-axle trucks

• Practical choice:

  • DBM with VG-40

  • BC and SMA wearing course with PMB as per BIS 15462 service category

  • WMA technology if haul distances are long, to retain workability

2) Upgraded PMGSY road in coastal Kerala

• Climate: High rainfall, moderate temperatures, potential waterlogging

• Traffic: 1–3 msa, passenger vehicles and light goods

• Practical choice:

  • Emulsion-based macadam and DBM/BC with VG-30

  • Strong tack coat and drainage design to avoid stripping

  • Optionally use waste plastic-modified wearing course on steeper gradients for durability, following IRC:SP:98.

On-Site Lessons: Indian Case Studies

Case 1 – High-speed highway with recycled materials

On the Ghaziabad–Aligarh Expressway, contractors laid 100 lane-km of bituminous concrete in 100 hours while using Cold Central Plant Recycling to reuse about 90% milled material. For such projects, using VG-40 or PMB in the wearing course is crucial to resist deep rutting and shear stresses from high-speed, heavy traffic.

Practical lessons:

• Stiffer binders need careful temperature control to avoid poor compaction.

• Recycled mixes with reclaimed asphalt pavement (RAP) benefit from WMA additives to reduce aging and maintain workability.

Case 2 – Rural plastic-bitumen roads

MoRTH and IRC guidelines allow the dry process addition of about 6–8% shredded waste plastic by weight of bitumen in wearing courses, particularly for service roads and rural links. Cities such as Delhi, Kolkata, and Ahmedabad are piloting and scaling plastic-modified roads to improve durability and manage waste simultaneously.

Key takeaways:

• The base binder must still meet VG specifications; plastic supplements, not replaces, bitumen.

• Temperature control (<180°C) prevents harmful emissions.

Case 3 – Municipal waste and highways

NHAI has already used around 80 lakh tonnes of municipal waste in various highway projects, including the Delhi–Mumbai corridor. While much of this waste goes into embankments and sub-base, it changes binder selection strategy:

• Heavier use of PMB or VG-40 in surfacing layers to compensate for heterogeneous lower layers

• More emphasis on crack-resistant binders and reflective-cracking control (e.g., interlayers + PMB BC)

Common Pavement Failures and the Role of Bitumen

Even well-designed Indian roads can fail early if binder choice and construction control don’t match the environment.

Table 3 – Typical Distresses and Bitumen-Related Remedies

On-site controls that protect binder performance:

• Strict plant temperature monitoring (overheating accelerates aging)

• Timely compaction within temperature window

• Correct tack coat rate and coverage to avoid slippage and delamination

• Periodic core cutting and density checks for QA

Emerging Trends: Greener, Smarter Bituminous Roads

Plastic-modified and waste-based roads

Beyond shredded plastic in wearing courses, India is piloting plastic geocells for difficult terrains, where 3D honeycomb cells made from waste plastic confine soil and aggregates to stabilise weak subgrades.

Guidelines such as IRC:SP:98 and related MoRTH circulars formalise waste-plastic use, and large volumes of municipal waste are also moving into road embankments, cutting landfill demand.

Warm mix asphalt (WMA) and energy-efficient construction

IRC’s interim guidelines on WMA recognise additives and foaming technologies that reduce mixing and compaction temperatures by about 20–40°C, lowering fuel use and emissions while improving workability.

For busy highway projects and urban night works, WMA paired with PMB offers:

• Faster opening to traffic

• Longer haul distances without cold spots

• Reduced fumes and better working conditions

Bio-bitumen and alternative binders

Several developments point toward a future where bitumen is partially renewable:

• Sugarcane molasses-based bio-bitumen has already paved a 650 m trial section on NH 709AD (Muzaffarnagar–Shamli) where up to 30% of the binder came from molasses, with good performance after monsoon exposure.

• A lignin bio-bitumen section on the Nagpur–Mansar bypass (NH 44) shows potential for up to 15% replacement of fossil bitumen and around 70% GHG reduction for that portion of the binder.

• Government-backed plans aim to scale biomass-derived bio-bitumen and reduce imported bitumen dependency over the coming decade.

For designers and buyers, this means binder specifications will increasingly include renewable content and carbon metrics, not just viscosity and softening point.