Bitumen Grade Equivalence Chart

There are three fundamentally different ways to classify a paving binder, and national systems pick one:

• By penetration — how far a needle sinks into the binder at 25 °C. Used by ASTM D946, EN 12591, Chinese JTG F40 and Russian GOST 22245, though each expresses it differently.
• By viscosity — how stiff the binder is at 60 °C, closer to real hot pavement temperature. Used by Indian IS 73:2013 and Australian AS 2008.
• By performance — whether the binder passes tests at the actual maximum and minimum pavement temperatures of the site. Used by Superpave PG grading.

Within the penetration family, conversion is usually straightforward because everyone is running the same ASTM D5 test. Between families it is not, and this is where most specification confusion in bitumen trade comes from. A viscosity number and a penetration number are not two ways of saying the same thing — they are measurements of different properties at different temperatures.

The naming conventions, decoded

• ASTM D946: the two numbers are the penetration range. 60/70 means penetration 60–70 dmm.
• EN 12591: same convention. 50/70 means penetration 50–70 dmm.
• Chinese JTG F40: a single number with a hash, such as 70#, is the nominal midpoint of a penetration band. 70# covers penetration 60–80 dmm.
• Russian GOST 22245: BND stands for viscous road petroleum bitumen. BND 60/90 is a penetration band of 60–90 dmm — a wider band than the ASTM equivalent.
• Indian IS 73:2013: VG-30 refers to a viscosity band at 60 °C, not penetration. The number is not a penetration value at all.
• Superpave: PG 64-22 means the binder passes its high-temperature criteria at 64 °C and its low-temperature criteria at -22 °C pavement temperature.

The word equivalent does a great deal of unearned work in bitumen trade. It suggests that two grade names describe the same material under two labels. They do not. They describe two specifications, written by different committees, that measure different properties, at different temperatures, on material aged by different laboratory procedures. Two cargoes can sit inside the same penetration band and one of them can fail the other system’s specification outright, with nobody having made a mistake. Here is how that happens.

1. The systems measure different properties

Penetration is an indentation test: a 100 g needle assembly, five seconds, 25 °C, result in tenths of a millimetre, under ASTM D5, EN 1426 or IS 1203. Absolute viscosity is a flow test at 60 °C in a vacuum capillary, under IS 1206 (Part 2) or ASTM D2171, reported in poise. Kinematic viscosity at 135 °C, under IS 1206 (Part 3) or ASTM D2170, is a flow test at mixing temperature, reported in centistokes. Performance grading is an oscillatory shear measurement in a dynamic shear rheometer (ASTM D7175) and a flexural creep measurement in a bending beam rheometer (ASTM D6648) at the design temperatures of the site.

None of those results can be computed from any of the others. A relationship between them exists for any one binder, but it is a property of that binder and its crude source, not a constant of the material. That is the fundamental reason the columns of the chart above are neighbours rather than equals.

2. They measure at different temperatures, and binders diverge as they warm

Penetration is measured at 25 °C. Softening point lands between roughly 30 and 63 °C depending on grade. Absolute viscosity is measured at 60 °C, close to real hot-pavement temperature. Kinematic viscosity is measured at 135 °C, close to mixing temperature. Two binders identical at 25 °C need not be identical at 60 °C, because they can differ in how fast they soften as they warm — their temperature susceptibility.

That susceptibility is quantified by the penetration index, from the Pfeiffer and Van Doormaal relation, which needs only two numbers already on the certificate: penetration P in dmm at 25 °C and ring-and-ball softening point T in °C.

• A = (log 800 – log P) / (T – 25)
• PI = (20 – 500A) / (1 + 50A)

Run it on two cargoes that both report penetration 65 dmm. The first has a softening point of 48 °C: A = 0.0474 and the penetration index is about -1.1. The second has a softening point of 54 °C: A = 0.0376 and the penetration index is about +0.4. Both sit inside ASTM 60-70 on penetration and inside EN 50/70 on both penetration and softening point. They are not the same binder, they will not carry the same load at 60 °C, and the difference is visible for free on paperwork you already hold. The penetration index is an engineering consistency indicator rather than a requirement of any of these specifications; straight-run paving bitumens usually compute to somewhere between -1 and +1.

3. They age the material differently before they judge it

Every one of these specifications sets limits on the binder after a laboratory ageing step meant to represent what happens in the mixing plant. They do not use the same step and they do not express the result the same way.

• ASTM D946 uses the thin film oven test, ASTM D1754: a static 50 g film in a shallow dish, five hours at 163 °C. The requirement is a minimum retained penetration — 52 % for grade 60-70.
• EN 12591 uses the rolling thin film oven test, EN 12607-1: a moving film continuously exposed to fresh air at 163 °C. The requirements are a maximum change of mass, a minimum retained penetration and a maximum increase in softening point.
• IS 73:2013 uses a rolling thin film oven test and expresses the requirement as a viscosity ratio at 60 °C after ageing, maximum 4.0 — a ratio of two viscosities, not a penetration at all.
• JTG F40 permits either the thin film oven test or the rolling thin film oven test, with limits on mass loss, retained penetration ratio and residual ductility.
• GOST 22245 expresses ageing as a maximum increase in softening point after heating.

A static film skins over and shields the material beneath it. A rolling film keeps presenting fresh surface to fresh air. The two procedures do not produce the same residue from the same binder, and the numbers they generate are not interchangeable. A certificate showing 54 % retained penetration after ASTM D1754 is not evidence of anything under EN 12591, and a viscosity ratio of 3.2 says nothing whatever about retained penetration. Where a cross-system supply is contemplated, the ageing test named in the destination specification has to be run, not converted.

4. The property that is not required is the property that fails

This is the clearest single demonstration that the chart is approximate. ASTM D946 sets no softening point requirement. Its table covers penetration, flash point, ductility, solubility and the thin film oven test residue. The 49–56 °C softening point band that appears on almost every export data sheet for 60/70 is commercial practice on refinery data sheets, not a requirement of the standard.

EN 12591 requires a softening point band for every grade. For 50/70 it is 46–54 °C. So a cargo measuring 68 dmm with a softening point of 45 °C — a penetration index of about -1.8, unusual but entirely real with some crude sources — is a fully compliant ASTM D946 60-70 and a failed EN 12591 50/70. Nothing was mis-tested and nobody was dishonest. The property that decided the outcome is simply not part of the specification the cargo was made to, so nobody had any reason to control it. This is what people mean, without knowing it, when they say a grade is equivalent but not interchangeable.

The same asymmetry runs in every direction. EN 12591 requires a Fraass breaking point by EN 12593, which no ASTM penetration grade measures. The GOST BND series carries low-temperature requirements that the plain BN series does not. JTG F40 caps wax content by distillation, and the cap differs between the A, B and C sub-grades. IS 73:2013 imposes both a viscosity band and a minimum penetration. Every one of those is a line the chart above cannot show, and every one of them has rejected a cargo that matched on penetration.

5. Band edges are softer than they look

A grade band has hard edges on paper and a measurement has a spread. Every ASTM and EN test method publishes a precision and bias section giving repeatability — the spread expected between two results by one operator on one apparatus — and reproducibility, the wider spread expected between two laboratories. A cargo whose true penetration is near 70 dmm can report inside 60-70 at the load port and outside it at destination, with neither laboratory wrong. Any mapping that depends on a value sitting at the very edge of a band is fragile for that reason alone, which is why the narrow ASTM bands map into wide GOST and EN bands more safely than the reverse. ASTM D3244 is the published practice for combining a supplier’s result and a receiver’s result into an assigned test value using the precision statement of the method concerned; naming it in the contract turns an argument into a calculation.

What the chart is genuinely for

None of this makes the chart useless. It tells you where to look for supply, which grades are worth testing against a specification, and which requests are hopeless before anyone spends money drawing a sample. What it does not do is close a specification. The chart narrows the search; the Certificate of Analysis, read line by line against the destination standard, is what closes it.

A performance grade such as PG 64-22 is not a description of the binder in isolation. It is a statement that the binder was tested and passed at two specific temperatures: it met its rutting criteria at a 64 °C high pavement temperature, and its cracking criteria at a -22 °C low pavement temperature.

Penetration at 25 °C carries no information about either of those temperatures. Two 60/70 binders from different crude sources and different processing routes can test as PG 64-16 and PG 64-22 — same penetration grade, materially different low-temperature performance. The difference only appears when you run the bending beam rheometer, and no amount of arithmetic on the penetration value will reveal it.

What this means in practice

• If a project specification is written in PG, ask for the actual DSR and BBR test report for the binder being offered. Not a claimed grade — the report.
• A supplier who asserts a PG grade without test data is asserting something nobody has measured.
• Conversion tables that map penetration grades to PG grades exist and circulate widely. Treat them as a starting hypothesis for sourcing, never as a compliance document.
• The same logic applies in reverse: holding a PG-graded binder does not let you claim a penetration grade unless the penetration test was actually run.

Penetration, viscosity and softening point are all answers to the same question: how stiff is this binder. None of them answers how it behaves with the aggregate it will be mixed with, how fast it hardens in service, or what it does in a hot tank between arrival and use. Four properties sit outside every chart on this page, and each of them has failed a job that matched on grade.

• Adhesion to the local aggregate. Stripping is an interaction between a particular binder and a particular stone, not a property of either alone. Two cargoes with identical penetration can behave differently against the same siliceous aggregate. It is measured on the actual pair — boiling water stripping by ASTM D3625, or retained tensile strength on a compacted specimen by AASHTO T 283 — and an anti-stripping additive is specified against that result, never against a grade name.
• Wax content. JTG F40 caps it and GB/T 15180 caps it. No ASTM or EN paving grade requires it to be measured at all, so an origin certificate written to ASTM will normally be silent on it, and a cargo that matches a Chinese specification on every penetration line can still be rejected on wax alone. This is the clearest case on the page of a destination requirement that the origin standard never asked anyone to control.
• Ageing behaviour. Two binders at the same penetration can lose very different amounts of it in the mixing plant. Retained penetration, change of mass and viscosity ratio are the only lines on a certificate that speak to it, and as section three above sets out, each system measures them by a different oven procedure and reports them in a different quantity. A grade match tells you nothing here.
• Storage stability. Chiefly a modified-binder question, where separation in a hot storage tank is a real failure mode that no penetration figure predicts. It matters most when the substituted material is polymer modified and the specified material was not, or the reverse — a difference the grade names on both sides can hide completely.

Where a project is large enough for any of these to decide the outcome, the answer is not a better chart. It is a mix design run with the actual binder and the actual aggregate, closed before the grade question is closed rather than after the cargo has sailed. The chart narrows the field to a handful of candidates worth testing; the mix design chooses between them. The next section sets out how to write that result into an enquiry and then into a contract, when the enquiry itself arrives written in a system you cannot supply.