Bitumen looks like a single, uniform material — the black binder that holds asphalt roads together — but it is sold in dozens of distinct grades, and choosing the wrong one is an expensive mistake. Too soft, and a road ruts and bleeds in summer heat; too hard, and it cracks in winter cold. To make the choice systematic, the industry grades bitumen in three main ways: by penetration, by viscosity, and by performance. They are not competing products so much as three languages for describing the same petrochemical binder. This explainer walks through each system, shows how to read the numbers, and sets out how buyers match a grade to the job.
The short version
Penetration grade (e.g. 60/70) ranks bitumen by how far a needle sinks at 25°C — higher number, softer binder. Viscosity grade (VG10, VG30, VG40) ranks it by thickness at 60°C — higher number, stiffer binder. Performance grade (e.g. PG 64-22) brackets the actual high and low road temperatures the binder must survive. All three describe hardness and temperature behaviour; they just measure it differently.
Penetration grade: the needle test
Penetration grading is the oldest and still the most widely used system across the Middle East, Europe and much of Asia. The test is delightfully simple: a standard 100-gram needle is allowed to sink into a sample of bitumen for five seconds at 25°C, and the depth it reaches is measured in tenths of a millimetre, or dmm. A grade written as 60/70 means the needle penetrates between 60 and 70 dmm. The logic follows directly: a higher penetration number means a softer binder, and a lower number a harder one. So 40/50 is a hard grade for hot climates and heavy loads, 60/70 a general-purpose paving grade for moderate conditions, and 80/100 or 100/150 softer grades better suited to cold regions where flexibility and crack resistance matter. Penetration grades are usually paired with a softening point — commonly in the 49–56°C range for paving grades — under standards such as EN 12591 and the relevant ASTM methods.
"Higher penetration means softer bitumen; higher VG or PG means stiffer. Every grading system is really answering one question — how will this binder behave hot and cold?"
Viscosity grade: measuring the flow at 60°C
Viscosity grading was introduced to describe bitumen by a more fundamental engineering property — how it flows at the high service temperature of a road. Under the Indian standard IS 73, which moved from penetration to viscosity grading in 2006, bitumen is graded by its viscosity at 60°C, with the number giving the value in decapoise. The common grades tell a clear story of increasing stiffness: VG10 is the softest, used for prime and tack coats and for spray applications in cooler conditions; VG30 is the workhorse heavy-duty paving grade, well suited to hot and rainy climates; and VG40 is the stiffest, chosen for high-stress locations such as intersections, toll plazas and truck-parking areas, where a stiffer mix resists shoving and rutting under slow, heavy traffic. Because viscosity is measured at the temperature a road actually reaches in service, VG grading correlates better with in-service behaviour than a room-temperature needle alone.
Performance grade: bracketing the climate
Performance grading is the most modern system, developed out of the American SHRP research programme and its Superpave (Superior Performing Asphalt Pavements) framework. Instead of one number at one temperature, a performance grade brackets the whole climate the pavement will face. A grade such as PG 64-22 means the binder is engineered to resist rutting up to a 64°C pavement temperature and thermal cracking down to −22°C. Engineers therefore select a PG grade directly from the hottest and coldest pavement temperatures expected at the site, often with a safety margin for heavy or slow traffic. This is why PG binders — frequently polymer-modified — dominate demanding highway and airfield work: the grade is a promise about real-world performance across the temperature range, not just a single lab reading.
The three systems side by side
The table below summarises how the systems differ. In practice a buyer rarely converts between them precisely — a 60/70 penetration binder is broadly comparable to VG30, but the systems test different things and are not exactly equivalent, so the safe approach is to specify to the grade your project's standard actually calls for.
| System | What it measures | Example grades | Typical use |
|---|---|---|---|
| Penetration | Needle depth at 25°C (dmm); higher = softer | 40/50, 60/70, 80/100 | General paving bitumen; Middle East, Europe, Asia |
| Viscosity (VG) | Viscosity at 60°C (decapoise); higher = stiffer | VG10, VG30, VG40 | Road works graded by climate & traffic (India, IS 73) |
| Performance (PG) | High & low pavement temperature limits | PG 64-22, PG 70-10 | Highways, airfields; climate-matched, often modified |
| Oxidised / blown | Softening point & penetration (e.g. R 85/25) | 85/25, 90/40, 115/15 | Roofing, waterproofing, industrial — not paving |
How buyers choose the right grade
The decision comes down to two questions — how hot and cold does the site get, and how heavy is the traffic — followed by a third: which standard governs the project. Hot climates and heavy, slow-moving loads point to a harder, stiffer binder (a lower-penetration grade, a higher VG, or a higher upper-PG number) to resist rutting; cold climates point to a softer binder that stays flexible and resists thermal cracking. Then the grade is written in the language the local specification uses — penetration across much of the GCC and Europe, VG in India, PG in the United States. Whichever system applies, the discipline is the same: buy against a datasheet that states penetration or viscosity, softening point and ductility, and confirm each shipment with a certificate of analysis. Off-spec bitumen is a false economy — it shortens pavement life and voids warranties. Verifying supplier certificates against the grade is exactly the role of our quality assurance teams, backed by the global sourcing and logistics network that moves temperature-sensitive bitumen reliably to site.
Frequently asked questions
What does a bitumen grade like 60/70 actually mean?
It is a penetration grade. A standard 100-gram needle is allowed to sink into the bitumen for five seconds at 25°C, and the depth is measured in tenths of a millimetre (dmm). A 60/70 grade means the needle penetrates between 60 and 70 dmm. A higher number means a softer binder and a lower number a harder one, so 40/50 is harder than 60/70, which in turn is harder than 80/100.
What is the difference between penetration, viscosity and performance grading?
They are three ways of describing the same product. Penetration grading ranks bitumen by how far a needle sinks at 25°C. Viscosity grading (VG) ranks it by how thick it is at 60°C, in decapoise. Performance grading (PG, from the Superpave system) is the most modern: it tests the binder at the high and low temperatures the road will actually see, so the grade is tied to climate rather than to a single lab number.
What do VG10, VG30 and VG40 mean?
They are Indian-standard viscosity grades (IS 73) measured at 60°C, with the number giving viscosity in decapoise. VG10 is the softest, used for prime and tack coats and colder conditions; VG30 is the general-purpose heavy-duty paving grade for hot and rainy climates; VG40 is the stiffest, chosen for high-stress locations such as intersections, toll plazas and truck-parking areas where resistance to rutting matters most.
How do I read a performance grade such as PG 64-22?
The first number is the high-temperature rating and the second the low. PG 64-22 means the binder is designed to resist rutting up to a 64°C pavement temperature and to resist thermal cracking down to −22°C. Because PG grades bracket the climate directly, engineers pick them from local high and low pavement temperatures rather than from a needle or viscosity value.
Which bitumen grade should I buy?
Start from climate and traffic. Hot climates and heavy traffic call for a harder, stiffer binder (a lower-penetration grade, a higher VG, or a higher-temperature PG) to resist rutting; cold climates need a softer binder that stays flexible and resists cracking. Then match the grade to the local specification — penetration in much of the Middle East and Europe, VG in India, PG in the United States — and always buy against a datasheet with penetration or viscosity, softening point and, ideally, a certificate of analysis.
Sourcing bitumen and petrochemicals with Arian Holding
Bitumen sits within Arian Holding's wider petrochemicals and chemicals line, alongside urea, sulphur, methanol and base oils — and next to the aggregates that go into the asphalt mix and the steel and polymer products that meet it on major infrastructure projects. Our trade desk helps buyers translate a road or waterproofing specification into a precise, certified order: the right penetration, VG or PG grade, verified against the governing standard and delivered on schedule through our logistics network. Explore the range in our Petrochemicals catalogue, part of our Industrial Products & Commodities sector, then request a quote with your grade, volume and destination.
Sources: ASTM & EN 12591 penetration-grade bitumen specifications; Bureau of Indian Standards IS 73:2013 (viscosity grades); AASHTO / Superpave (SHRP) performance-grade binder specification; Bitumen grades VG10/VG30/VG40 overview; Penetration grade 60/70 vs 80/100; Bitumen VG vs PG grading. Grade values are indicative and provided for general information only; always confirm against the current standard edition and the product datasheet — this is not engineering or trading advice.