Bitumen 50/70 — Specification, Production & Applications
Bitumen 50/70 is the European reference paving grade, specified across a wide band of temperate and warm climates for general road construction.
Where Bitumen 50/70 sits among the penetration grades
Penetration is measured as the depth in tenths of a millimetre that a standard needle penetrates the binder in five seconds at 25 °C under a 100 g load, to ASTM D5. A lower number means a harder binder. The scale above runs from hard on the left to very soft on the right.
What defines Bitumen 50/70
Penetration of 50 to 70 at 25 °C places it marginally harder than 60/70 while overlapping it substantially. In practice the two are close substitutes, and which one a tender names is more often a matter of which standard the specifying authority follows than of any real difference in the material.
The values that matter
The 58 per cent retained penetration requirement after the thin film oven test is the value that separates a durable 50/70 from a marginal one. It measures how much of the original softness survives short-term ageing during mixing and laydown. A binder that passes the fresh penetration window but retains less than 58 per cent will harden fast in service.
How Bitumen 50/70 is produced
Refining route
Bitumen 50/70 is straight-run vacuum residue taken at a conventional cut depth. Crude is fractionated at atmospheric pressure, the long residue goes to a vacuum column, and the residue remaining after the heavy gas oils are stripped is the base binder. For most conventional crude slates this lands close to the 50/70 window without further processing.
Blend and release control
Where a single stream falls outside the window, the correction is tank blending: a harder and a softer residue are circulated together until the penetration and softening point both fall inside the envelope, then the blend is re-tested. The certificate applies to the blended product as loaded, not to the component streams.
Bitumen 50/70 specification
| Property | Test method | Unit | Requirement |
|---|---|---|---|
| Density @ 25 °C | ASTM D70 | g/cm³ | 1.01–1.06 |
| Penetration @ 25 °C, 100 g, 5 s | ASTM D5 | ×0.1 mm | 50–70 |
| Softening point, ring and ball | ASTM D36 | °C | min 52 |
| Ductility @ 25 °C | ASTM D113 | cm | min 100 |
| Loss on heating | ASTM D6 | wt % | max 0.8 |
| Retained penetration after heating | EN 1426 | % | min 58 |
| Solubility in trichloroethylene | ASTM D2042 | wt % | min 99 |
| Flash point, Cleveland open cup | ASTM D92 | °C | min 250 |
| Spot test | AASHTO T102 | — | negative |
A certificate of analysis accompanies every shipment. Independent inspection by SGS, Intertek or an equivalent surveyor can be arranged at the buyer instruction and account.
Where Bitumen 50/70 is used
General road construction
Wearing and binder courses across temperate and warm climates, the highest-volume application for this grade.
Asphalt plant supply
Continuous supply to hot mix plants producing dense-graded and stone mastic mixtures.
Surface dressing
Chip seal and surface treatment work where a mid-range binder gives the required adhesion and flexibility.
Pavement rehabilitation
Overlays and structural repairs on existing road networks.
Airport pavements
Runway and taxiway surfacing where the specifying standard is written in penetration terms.
Municipal works
City and provincial road programmes procured against European or equivalent standards.
Handling and application temperatures
Working temperatures follow the binder viscosity rather than the grade designation alone. The ranges below are typical starting points for Bitumen 50/70 and should be confirmed against the mix design.
| Operation | Typical range | Control note |
|---|---|---|
| Bulk storage | 150–170 °C | Circulate to avoid local overheating at the coils |
| Pumping and transfer | 150–170 °C | Confirm line tracing before transfer begins |
| Hot mix asphalt mixing | 150–165 °C | Per mix design, not per binder alone |
| Compaction | 130–150 °C | Cease rolling below the lower figure |
| Maximum sustained heating | below 180 °C | Above this, oxidative hardening accelerates sharply |
Drummed material should be reheated in a controlled oven or hot room rather than by direct flame. Localised overheating hardens the binder at the drum wall and can take a compliant parcel out of specification before it reaches the mixer.
Available packing for Bitumen 50/70
| Packing | Net weight | Loading per 20 ft FCL | Typical use |
|---|---|---|---|
| New steel drum | 150 / 180 / 185 / 200 kg | 110 drums, 20.35 MT at 185 kg | Smaller parcels, sites without bulk storage |
| Jumbo bag | 1 MT | 20 MT | Lower packing cost, requires melting facility |
| Flexitank / bitutainer | 20–22 MT | 1 unit | Bulk economics without a bulk vessel |
| Bulk vessel | by parcel | heated tanker | Terminal to terminal, largest volumes |
As a Bitumen 50/70 supplier Bitumen Asphaltive ships on CFR, CIF and FOB terms with commercial invoice, packing list, bill of lading, certificate of origin and certificate of analysis.
Questions about Bitumen 50/70
What is the practical difference between 50/70 and 60/70?
Very little in service. The windows overlap across 60 to 70, so a single parcel can satisfy both specifications. The distinction is largely which standard the buyer works to. If a tender permits either, ask for both prices, because availability rather than performance usually decides which is cheaper in a given month.
Why is retained penetration after heating specified at 58 per cent?
Because it measures ageing resistance rather than fresh consistency. During mixing and laydown the binder is held near 160 °C in a thin film with air present, and it hardens. Requiring at least 58 per cent of the original penetration to survive that ensures the binder reaching the road is not already substantially aged.
Is 50/70 suitable for cold climates?
It is more tolerant than the harder grades, but penetration grading does not certify low-temperature behaviour at all. If winter cracking is a design concern, a performance grade with an explicit low-temperature limit gives a defensible specification where a penetration grade does not.
What loss on heating is acceptable?
A maximum of 0.8 per cent by mass under ASTM D6. A higher figure indicates volatile content that will be lost in the mixer, changing the binder consistency between the certificate and the road.
The penetration grade range
Penetration windows overlap between adjacent grades, so a single parcel can sometimes satisfy two specifications. Ageing limits and softening point are what separate them.
| Grade | Penetration @ 25 °C | Character |
|---|---|---|
| Bitumen 20/30 | 20–30 × 0.1 mm | Hard |
| Bitumen 30/40 | 30–40 × 0.1 mm | Hard |
| Bitumen 40/50 | 40–50 × 0.1 mm | Medium hard |
| Bitumen 50/70 | 50–70 × 0.1 mm | Medium hard |
| Bitumen 60/70 | 60–70 × 0.1 mm | Medium hard |
| Bitumen 70/100 | 70–100 × 0.1 mm | Medium soft |
| Bitumen 80/100 | 80–100 × 0.1 mm | Medium soft |
| Bitumen 85/100 | 85–100 × 0.1 mm | Medium soft |
| Bitumen 120/150 | 120–150 × 0.1 mm | Soft |
| Bitumen 200/300 | 200–300 × 0.1 mm | Very soft |
Speak to a Bitumen 50/70 supplier
Send quantity in metric tonnes, required packing, destination port and preferred Incoterm. Offers are normally returned within one working day.