Oxidized bitumen 105/35 occupies the most useful position in the blown bitumen range: a softening point around 105 °C with a penetration of roughly 35 dmm. That combination is unusual and it is the whole point of the grade. Most binders that resist 105 °C are brittle at ambient temperature. This one is not. It is the grade specified when a membrane has to survive a summer roof without flowing, and a winter without cracking.
RAHA Gilsonite supplies oxidized bitumen 105/35 against ASTM D312 or against a buyer’s own specification where a project standard applies. This page sets out the specification, why the softening point to penetration ratio matters more than either figure alone, the melting and application temperatures, and how the grade compares with the alternatives either side of it.
What is oxidized bitumen 105/35?
Oxidized bitumen, also called blown bitumen or blown asphalt, is produced by blowing air through hot penetration grade bitumen at around 240 to 260 °C. Oxygen reacts with the maltene fraction and converts it toward asphaltenes. The binder becomes harder, the softening point climbs and the penetration falls.
Reading the grade designation
The designation reads softening point over penetration. In oxidized bitumen 105/35, the 105 is the ring and ball softening point in degrees Celsius and the 35 is the penetration at 25 °C in tenths of a millimetre. Both carry a tolerance, which is why the specification below shows ranges rather than single figures.
Why the ratio matters more than either number
Two grades can share a softening point and behave completely differently. Oxidized bitumen 105/15 has the same 105 °C softening point as 105/35, but a penetration of only 15 dmm. It is much harder and much less forgiving of movement.
The gap between those two numbers describes the binder’s temperature susceptibility — how much its consistency changes as temperature changes. A grade with a high softening point and a relatively soft penetration has been blown in a way that raises heat resistance without destroying low-temperature flexibility. That is what makes 105/35 the preferred grade for membrane manufacture, and why substituting 105/15 into a membrane formulation produces sheets that crack at the fold.
The practical test. If your application involves any movement — a roof that expands and contracts, a membrane that gets rolled and unrolled, a joint that opens in winter — the penetration figure matters as much as the softening point. If the application is static and only needs heat resistance, a harder grade will do and usually costs less.
Oxidized bitumen 105/35 specification
| Property | Unit | Specification | Typical result | Test method |
|---|---|---|---|---|
| Softening point (ring & ball) | °C | 100–110 | 105 | ASTM D36 |
| Penetration @25 °C, 100 g, 5 s | dmm | 30–40 | 35 | ASTM D5 |
| Loss on heating | wt % | 0.5 max | 0.2 | ASTM D6 |
| Flash point (Cleveland open cup) | °C | 250 min | 280 | ASTM D92 |
| Solubility in trichloroethylene | wt % | 99 min | 99.5 | ASTM D2042 |
| Specific gravity @25 °C | — | 1.00–1.06 | 1.03 | ASTM D70 |
| Ductility @25 °C | cm | Report | 2–4 | ASTM D113 |
| Ash content | wt % | 0.5 max | 0.2 | ASTM D2939 |
Unlike the harder blown grades, 105/35 retains measurable ductility and it is worth having on the certificate for membrane applications. Full test method definitions are maintained by ASTM International. Where a project specification differs from the values above, send us the specification rather than the grade name and we will confirm what meets it.
Applications of oxidized bitumen 105/35
The applications below all need heat resistance combined with some retained flexibility. That is a narrower requirement than it sounds, and it is why this grade sells in volume.
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Roofing felt and membrane
The largest single use. Coating and impregnation compound for bitumen felt, torch-on membrane and built-up roofing systems. High softening point prevents summer flow; retained penetration prevents winter cracking.
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Waterproofing compounds
Below-grade waterproofing, tanking, basement and foundation protection where the substrate may move.
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Damp proof course
DPC sheet manufacture, where the material must be rolled, unrolled and laid without fracturing.
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Adhesives and bonding compounds
Bituminous adhesives for membrane laying, board bonding and general construction use.
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Joint and crack sealing
Pourable sealants for pavement joints and building expansion joints where the joint opens and closes seasonally.
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Construction mastics
Filling and jointing compounds for tanks, ducts, flooring and industrial substrates.
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Pipe coating
Hot-applied enamel for buried pipe, usually at the softer end of the range where the pipe will flex during laying.
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Sound damping and undersealing
Automotive and appliance damping compounds where the panel vibrates and a brittle compound would delaminate.
Where a different grade is the better answer
If the application is static and only needs heat resistance — electrical potting compound, battery sealing, briquette binder — a harder grade such as 115/15 or 150/5 does the job and usually costs less per tonne of performance. If the climate is cold and the roof is exposed, 90/40 or 85/40 give more flexibility at the price of some heat resistance. Tell us the climate and the substrate at the enquiry stage and we will say which fits.
How 105/35 compares with the other oxidized grades
Reading down this table is the quickest way to confirm whether 105/35 is really the grade your specification needs.
| Grade | Softening point | Penetration | Class | Principal use |
|---|---|---|---|---|
| 150/5 | 145–155 °C | 0–10 dmm | Hardest | Electrical compounds, battery sealing, pipe enamel, rubber |
| 115/15 | 110–120 °C | 10–20 dmm | Hard | Waterproofing, adhesives, sealing compounds, pipe coating |
| 105/35 | 100–110 °C | 30–40 dmm | Medium | Roofing felt, membrane, waterproofing, general adhesive work |
| 105/15 | 100–110 °C | 10–20 dmm | Hard | Sealing, jointing, industrial mastics. Same heat resistance, far less flexible |
| 95/25 | 90–100 °C | 20–30 dmm | Medium | Roofing membrane, damp proofing |
| 90/40 | 85–95 °C | 35–45 dmm | Softer | Roofing felt, membrane manufacture in cooler climates |
| 90/15 | 85–95 °C | 10–20 dmm | Medium | Adhesive and sealing work |
| 90/10 | 85–95 °C | 5–15 dmm | Hard | Pipe coating, industrial compounds |
| 85/40 | 80–90 °C | 35–45 dmm | Softer | Membrane, roofing, damp proof course |
| 85/25 | 80–90 °C | 20–30 dmm | Medium | The volume roofing grade worldwide |
| 75/35 | 70–80 °C | 30–40 dmm | Softest | Damp proofing, low-temperature climates |
| 75/25 | 70–80 °C | 20–30 dmm | Softest | General waterproofing, jointing |
The full range is listed on our oxidized bitumen grades page.
105/35 against 85/25, the volume roofing grade
85/25 is the most widely sold roofing grade in the world and the natural comparison. The difference is 20 °C of softening point. In temperate climates 85/25 is entirely adequate and costs less. In the Gulf, North Africa, South Asia or anywhere a dark roof surface exceeds 80 °C in summer, 85/25 will soften and flow at the laps, and 105/35 is the correct specification. If your membrane is being sold into a hot market, this is the grade upgrade that prevents warranty claims.
Melting and application temperatures
| Operation | Temperature | Notes |
|---|---|---|
| Melting | 170–195 °C | Indirect heating. Melt the full charge and homogenise before drawing off |
| Pumping | 180–200 °C | Lines heat traced. The grade sets quickly in cold pipework |
| Coating / application | 190–215 °C | Membrane coating lines typically run at the upper end for even film thickness |
| Absolute maximum | 230 °C | Above this the softening point drifts upward and the penetration falls — you lose the property you bought the grade for |
| Hot holding | Limit to a working shift | Prolonged holding hardens the grade further. Melt per batch where possible |
Overheating this grade is self-defeating. The reason to buy 105/35 rather than 105/15 is the retained penetration. Holding it above 230 °C for a shift can drop the penetration by several points, at which stage you have paid for 105/35 and are running 105/25 through your coating line. Log the tank temperature and check the penetration on the finished sheet, not only on the incoming material.
Safety
The flash point is 250 °C minimum, so there is margin against the working range, but fume generation and thermal burn risk are real at these temperatures. If the material foams, spits or crackles as it heats, water is present — stop heating rather than trying to drive it off. Handling guidance for bituminous binders is published by Eurobitume and the Asphalt Institute.
Packing, storage and shipping
| Packing | Unit weight | Per 20′ container | Notes |
|---|---|---|---|
| Kraft paper bag | 25 kg | Up to 25 MT palletised | Most common. Meltable bag options available so the bag goes into the melter |
| Carton | 25 kg | Up to 22 MT | Better protection for long transit and rough handling |
| New steel drum | 180–190 kg | 80 drums ≈ 15 MT | Requires cutting or a drum melter at destination |
| Jumbo bag | 1,000 kg | Up to 22 MT | Lowest packing cost per tonne where handling equipment exists |
Storage and shelf life
Two to three years in sealed packing kept dry and out of direct sun. Because the material is already blown there is little left for atmospheric oxygen to react with, so chemical ageing runs slowly.
The realistic problem with 105/35 is physical and it is worse than with the harder grades. At a penetration of 35 dmm the blocks are softer, and in hot climates a stack under pressure will fuse into a single mass that has to be broken up before it can be charged into a melter. Store on pallets, under cover, no more than two tiers high, and avoid leaving pallets in direct sun in Gulf or equatorial conditions.
Customs classification
The grade falls under HS 2713.20, petroleum bitumen. Bagged and drummed material at ambient temperature is generally not classified as dangerous goods for sea carriage, although most shipping lines and destination customs still require the safety data sheet with the booking.
Quality control and certification
Every shipment leaves with a batch certificate of analysis stating the lot number, the production date, the standard tested against and each test with its method and measured result. We accept third-party inspection at loading by SGS, Bureau Veritas, Intertek or any surveyor named in your contract.
What to check on the certificate for this grade specifically
Read softening point and penetration together, and check both against the batch rather than against the grade range. A binder that comes in at 109 °C softening point with 31 dmm penetration technically passes 105/35, but it is at the hard corner of the specification and will behave more like 105/15 in a membrane line. If your process is sensitive, ask for a tighter window in the contract — for example 103–107 °C with 33–38 dmm — rather than accepting the full range.
Frequently asked questions about oxidized bitumen 105/35
What does 105/35 mean in oxidized bitumen?
The first number is the ring and ball softening point in degrees Celsius, so approximately 105 °C. The second is the penetration at 25 °C in tenths of a millimetre, so approximately 35 dmm. The specification runs 100–110 °C for softening point and 30–40 dmm for penetration.
What is oxidized bitumen 105/35 used for?
Principally roofing felt and membrane manufacture, plus waterproofing compounds, damp proof course sheet, bituminous adhesives, joint and crack sealants, construction mastics, pipe coating and sound damping compounds. What these share is a need for heat resistance combined with retained flexibility.
What is the difference between 105/35 and 105/15?
They share the same softening point of around 105 °C but not the same penetration — 30 to 40 dmm against 10 to 20 dmm. 105/35 stays flexible enough to be rolled, folded and laid without cracking, which is why it is used for membrane. 105/15 is much harder and belongs in static applications such as sealing compounds and industrial mastics. They are not interchangeable in a membrane formulation.
Can I use 105/35 instead of 85/25 for roofing?
Yes, and in hot climates you should. 85/25 is the global volume roofing grade and works well in temperate conditions, but its softening point of 80 to 90 °C is not enough where a dark roof surface exceeds 80 °C in summer. In the Gulf, North Africa, South Asia and similar markets, 105/35 prevents softening and flow at the laps.
What temperature do I melt oxidized bitumen 105/35 at?
Melt at 170 to 195 °C, pump at 180 to 200 °C and coat or apply at 190 to 215 °C, using indirect heating. Do not exceed 230 °C. Overheating drives the penetration down, which removes the flexibility that distinguishes this grade from the harder ones.
Is oxidized bitumen 105/35 the same as blown asphalt 105/35?
Yes. Oxidized bitumen, blown bitumen and blown asphalt all describe the same product — penetration grade bitumen air-blown at high temperature to raise the softening point and reduce the penetration. The naming varies by region rather than by product.
What is the shelf life of oxidized bitumen 105/35?
Two to three years in sealed packing kept dry, on pallets and out of direct sun. Chemical ageing is slow because the material is already blown. The practical limit is physical: at 35 dmm penetration the blocks are soft enough to fuse together under stacking pressure in hot climates, so limit stacks to two tiers and keep pallets shaded.
Does 105/35 have measurable ductility?
Yes, typically 2 to 4 cm at 25 °C, unlike the harder blown grades where ductility is not specified because the material fractures rather than stretches. For membrane applications it is worth having the figure on the certificate, since it is a direct indicator of whether the sheet will crack when folded.
What is the HS code for oxidized bitumen?
HS 2713.20, petroleum bitumen, which covers all oxidized and penetration grades. National tariffs add further digits, so confirm the full code with your customs broker. Note that gilsonite and other natural bitumen fall under a different heading.
What is the minimum order quantity?
One full 20′ container, roughly 22 to 25 MT depending on packing. Mixed grades in one shipment are accepted provided each grade reaches one full container. Loading is from Jebel Ali, Mersin or Bandar Abbas on FOB, CFR or CIF terms.
Can you supply against a tighter specification than the standard range?
Yes. Where your process is sensitive to where the material sits within the 100–110 °C and 30–40 dmm windows, we can contract to a narrower band. Say so at the enquiry stage rather than after the first shipment, since it affects which production batch is allocated.
Related grades and technical pages
Adjacent grades: oxidized bitumen 115/15 and 105/15 for harder work, 95/25, 90/40 and 85/25 for softer or cooler-climate membrane. The complete list is on the oxidized bitumen grades page.
Where a compound needs additional hardness, gloss or a higher softening point than blown bitumen alone can deliver, gilsonite is frequently blended in — see gilsonite specification, gilsonite in paint and gilsonite in asphalt. For the difference between air-blown and naturally occurring hard bitumen, see natural bitumen and gilsonite bitumen.
Request a quotation for oxidized bitumen 105/35
Send us the quantity, packing, discharge port and the specification your contract names. Tell us the climate the finished product will serve and we will confirm whether 105/35 is the right grade or whether something either side of it suits better. Batch certificate of analysis with every shipment, third-party inspection accepted at loading.
Dubai: No. 2305, Burlington Tower, Business Bay — +971 4 566 4998
Ankara: Karşıyaka District, 749 Street No. 30, Gölbaşı 06830 — +90 312 544 5481
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