Cutback Bitumen MC 250 — Specification, Production & Applications
Cutback Bitumen MC 250 is a medium-curing binder of penetration-grade bitumen cut back with roughly a third of its volume in kerosene-class distillate, bought by cold-mix producers, stockpile patch manufacturers and off-plant maintenance contractors.
Reading the grade
MC 250 is defined by a kinematic viscosity of 250 to 500 mm2/s at 60 C (ASTM D2170) and a distillation residue of at least 67% by volume, so roughly a third of what is delivered is solvent. Its immediate neighbours differ in solvent loading rather than in chemistry: MC 70 leaves only 55% residue, MC 800 leaves 75%. That single step changes behaviour completely. MC 70 is thin enough to soak into a tight granular base and is bought to prime. MC 250 is the lowest MC grade carrying enough body to coat aggregate and hold it, which makes it a mixing binder rather than a penetrating one.
What buyers should know
The flash point is where MC 250 breaks cleanly from the lighter grades. MC 30 and MC 70 are specified at minimum 38 C by Tag open cup (ASTM D3143); MC 250 steps up to minimum 66 C, reflecting a heavier front end in the solvent cut. That changes what a buyer is actually signing for: different tank farm rules, different site fire precautions, different packing group assumptions under UN 1999. Commercially, the point rarely made on supplier pages is that freight, duty, storage and handling are all paid on a volume that is one third solvent, and that solvent is destined for the atmosphere.
How Cutback Bitumen MC 250 is produced
Feedstock and process
MC 250 is a blend, not a conversion product. A penetration-grade base binder is drawn at around 100 to 135 C and a kerosene-class distillate is metered into it under circulation, solvent into hot binder rather than the reverse, in a closed blender held below the flash point of the developing mixture. The base grade is chosen by working backwards from the residue specification: after ASTM D402 distillation the recovered residue must penetrate 120 to 250 dmm at 25 C, hold at least 100 cm ductility at 25 C and be at least 99% soluble in trichloroethylene. Nothing in the process alters the bitumen itself. The asphaltene and maltene balance of the base binder passes through the blend unchanged, which is the fundamental difference between cutting back and air blowing.
What changes in the binder
The letters carry the solvent class. MC means medium curing and is produced by cutting with a kerosene-type distillate boiling roughly 150 to 300 C. RC grades use a naphtha or gasoline-range cut and flash off in hours; SC grades use a heavy gas oil or road oil and cure over months, largely by absorption into the aggregate rather than by evaporation. The number is not a solvent percentage and not a hardness. It is the lower bound of the kinematic viscosity window at 60 C in mm2/s, and every MC grade runs from that figure to double it: 30 to 60, 70 to 140, 250 to 500, 800 to 1600, 3000 to 6000. Volatility of the cut sets the curing class; dosage of the cut sets the number.
Why it is not a paving grade
ASTM D402 distils a 200 mL sample and records the volume recovered at 190, 225, 260 and 316 C, reported as a percentage of total distillate to 360 C, with residue taken by difference. It is a volatility fingerprint, not a cure-time measurement. For MC 250 the correct ASTM D2027 column reads maximum 10% to 225 C, 15 to 55% to 260 C and 60 to 87% to 316 C. The tight ceiling on the light front end is what holds the flash point at 66 C and keeps a stockpiled mix pliable for months; the bulk of the solvent leaving in the middle band is what produces a field cure measured in days to weeks rather than the hours an RC grade gives.
Cutback Bitumen MC 250 specification
Written against the governing standard rather than reproduced from a supplier datasheet, so every limit below can be checked against the published requirement.
| Property | Test method | Unit | Requirement |
|---|---|---|---|
| Kinematic viscosity @ 60 °C | ASTM D2170 | mm²/s | 250–500 |
| Flash point, Tag open cup | ASTM D3143 | °C | min 66 |
| Water content | ASTM D95 | vol % | max 0.2 |
| Distillation to 360 °C — per cent of total distillate | |||
| to 225 °C | ASTM D402 | % | max 10 |
| to 260 °C | ASTM D402 | % | 15–55 |
| to 316 °C | ASTM D402 | % | 60–87 |
| Residue from distillation to 360 °C | ASTM D402 | vol % | min 67 |
| Tests on the distillation residue | |||
| Absolute viscosity @ 60 °C | ASTM D2171 | poise | 300–1200 |
| or penetration @ 25 °C, 100 g, 5 s | ASTM D5 | dmm | 120–250 |
| Ductility @ 25 °C | ASTM D113 | cm | min 100 |
| Solubility in trichloroethylene | ASTM D2042 | wt % | min 99.0 |
Where Cutback Bitumen MC 250 is used
Stockpile cold-patch mixtures
The capped light front end keeps an open pile of coated 6 to 14 mm aggregate workable through a winter. Strength develops only after placement, as traffic kneads the mat and the remaining kerosene works its way out.
Mix-in-place and travel-plant road mixes
At roughly a third solvent the binder film stays mobile enough to wet cold, slightly dusty aggregate on the grade, which a 75%-residue MC 800 will not do reliably at low ambient temperature without heating the stone.
Surface dressing and sand seals in hot, dry conditions
Chosen where a cationic emulsion would break before it has wetted dusty chippings, or where site water supply and emulsion storage temperature control are not available.
Prime coat on coarse, open-textured bases
Used where MC 30 or MC 70 drains away into a very open granular layer and leaves too little residue at the surface to bind the first seal, and in hot climates where lighter grades penetrate excessively.
Cold-weather tack and bond coats
MC 250 does not freeze, needs no above-freezing heated storage to stay homogeneous, and tolerates the sub-zero shoulder seasons that put emulsion tanks and distributor bars out of service.
Remote and off-plant maintenance
Shoulder repair, haul-road patching and airfield edge work where no hot mix plant sits within economic haul distance, and where drummed or IBC material must remain serviceable for months.
Storage, heating and handling
Store in a vented tank at a modest temperature and heat only with low-intensity indirect coils, never with an exposed flame or an element that can run dry. The minimum Tag open cup flash point is 66 C, while spray application temperatures commonly quoted for this grade reach around 105 C, so a vapour space above the flash point is a normal operating condition rather than a fault. Bond and earth all transfer lines, keep ignition sources clear of vents and hatches, and never admit water to a hot tank. When blending or adjusting, add solvent to binder, never binder to solvent.
Regulatory and safety context
Stated plainly, because a buyer who discovers this after purchase has a problem that content cannot fix.
Cutback bitumen is a regulated VOC source and buyers should treat that as a purchasing constraint. In the United States, state implementation plans following the EPA’s 1977 control techniques guideline for cutback asphalt restrict manufacture, storage and application during the ozone season, commonly from mid-April to mid-September, with defined exemptions for long-life stockpile patching mixtures, penetrating prime coats and work at low ambient temperature; exact dates, thresholds and exemption wording differ by state and air district. European practice has moved substantially to emulsions and fluxed binders under the EN 15322 framework. Physically, roughly a third of every tonne of MC 250 is kerosene-class solvent released to atmosphere during cure, which is simultaneously an emissions question, a lost-material cost and an occupational exposure question: kerosene vapour irritates the respiratory tract and skin, and the liquid presents an aspiration hazard. On fire risk, MC 250 is a flammable liquid, transported under UN 1999 (tars, liquid, including road oils and cutback bitumens), Class 3, with the packing group determined by the actual flash point and viscosity of the consignment. Because working temperatures can exceed the minimum flash point, open flames, hot work and unbonded transfer arrangements around storage and distributor equipment are genuine ignition risks rather than theoretical ones.
Available packing
| 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 | Standard for this product class |
| Meltable or kraft bag | 25 / 50 kg | by pallet configuration | Oxidized blocks, direct kettle charging |
| Flexitank / bitutainer | 20–22 MT | 1 unit | Bulk economics without a vessel |
| Bulk vessel | by parcel | heated tanker | Terminal to terminal |
As a Cutback Bitumen MC 250 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 Cutback Bitumen MC 250
Which distillation limits should I hold a supplier to for MC 250?
ASTM D2027 gives MC 250 a maximum of 10% of total distillate to 225 C, 15 to 55% to 260 C and 60 to 87% to 316 C, with residue minimum 67% by volume and residue penetration 120 to 250 dmm at 25 C. Data sheets circulating with max 20% to 225 C and 60 to 90% to 316 C have lifted those figures from the MC 70 column, and a residue penetration of 120 to 300 is not a D2027 limit for any MC grade. Check the certificate against the grade, not against the family.
MC 250 or MC 800?
MC 800 carries around a quarter solvent against MC 250’s third, is sprayed materially hotter, and develops cohesion faster. Choose it where traffic returns quickly, ambient temperatures are high, or wash-off risk is real. Choose MC 250 where mixing happens at ambient temperature, where aggregate is cold or dusty, or where a stockpile must survive months. The trade is symmetrical: MC 800 stiffens a winter pile towards an unworkable block, and MC 250 will not hold a chipping on a hot road as firmly.
Can a bitumen emulsion replace MC 250?
For tack, prime and surface dressing, usually yes, and regulators in several markets require it. Emulsions carry essentially no VOC load, need far less heat and cost less per tonne of residual binder. What they do not replicate is stockpile life. An emulsion cold mix breaks in the pile within weeks and cannot be mixed or placed in freezing weather. That single property is why cutback exemptions for long-life patching material and penetrating primes survive in regulations that otherwise prohibit the product.
How long does MC 250 take to cure in the field?
Days to weeks for a thin spray application in warm dry weather, and months for full solvent loss from a compacted cold-mix layer. The distillation curve indicates the rate but cannot predict it. Film thickness, aggregate absorption and porosity, ambient temperature, wind and rainfall all matter more than the laboratory numbers. Plan on a curing window, not a curing time, and expect a road-mix layer to hold measurable solvent, and therefore reduced stiffness, well into its first season.
Where is MC 250 restricted?
Across much of the United States cutback asphalt use is prohibited during the ozone season under state implementation plans derived from the EPA’s 1977 control techniques guideline, with carve-outs for long-life stockpile patching material, penetrating prime coats and low-ambient-temperature work. Dates and exemption wording vary by state and air district. European road authorities have largely displaced cutbacks with emulsions and fluxed binders framed by EN 15322. Confirm the destination rule before ordering, because the restriction usually falls on use and application, not only on manufacture.
Related grades and overviews
Speak to a Cutback Bitumen MC 250 supplier
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