CRS-2 Bitumen Emulsion: Specification, Chip Seal Use and Handling

CRS-2 is a cationic rapid-setting bitumen emulsion: paving bitumen torn into droplets typically quoted in the range of about 1 to 20 µm in a high-shear colloid mill and held in suspension in water by a positively charged emulsifier, so that a binder which will not pour at ambient temperature can be sprayed cold from a distributor bar. It is specified under ASTM D2397, Standard Specification for Cationic Emulsified Asphalt, and under the mirroring AASHTO M208. What is on the road twenty-four hours later is not the emulsion; it is the residue, the continuous bitumen film left behind once the emulsion has broken and the water has gone. The emulsion is the delivery system, and the residue is the product. Every commercial and technical judgement about CRS-2 follows from keeping those two things apart.

The general question of what an emulsion is, how a colloid mill makes one and why two compliant emulsions of the same designation can behave differently is covered on the bitumen emulsion hub page, and the full naming logic across every traded grade sits on bitumen emulsion grades. This page is about one grade, and about the operation that consumes most of it.

C — the sign of the charge

The leading C means cationic. The emulsifier is a fatty amine — a diamine, an amido-amine, an imidazoline or a quaternary ammonium compound — neutralised with hydrochloric acid. The amine head sits out in the water phase carrying a positive charge, the hydrocarbon tail buries itself in the bitumen droplet, and every droplet in the tank therefore wears the same positive charge. Like charges repel, and that mutual repulsion is the only thing holding the product together.

Two consequences follow immediately. The first is technical and is the reason the grade dominates world trade: a positively charged droplet is electrostatically attracted to the negatively charged surface of siliceous aggregate, which is most road stone. That is the subject of the next section. The second is practical and catches out buyers commissioning second-hand tankage. A cationic emulsion is acidic — typically in the region of pH 2 to 4, which is a characteristic of the product family rather than a limit ASTM D2397 places on it — and it attacks aluminium, zinc, galvanised coatings and copper alloys. Mild steel or stainless steel from the tank through the pump, the valves and the hose to the coupling, with no exceptions for a convenient brass fitting.

The charge is not asserted; it is measured. Particle charge to ASTM D244 passes a direct current between two electrodes in the emulsion and records which one the bitumen deposits on. Migration to the cathode means positively charged droplets and the result is reported positive. ASTM D7402 is the corresponding practice for identifying cationic emulsified asphalts. This is the only test that proves the family, and the difference between a cationic and an anionic emulsion is invisible in the drum and catastrophic in the tank.

RS — the setting class

RS means rapid setting. The grade is deliberately under-stabilised: it carries only as much emulsifier as it needs to survive manufacture, storage and transport, so that when it meets a mineral surface it gives up its charge and coalesces almost at once. That eagerness is quantified by demulsibility to ASTM D6936, in which 35 mL of 0.8 % sodium dioctyl sulfosuccinate solution is added to a measured quantity of emulsion and the proportion of bitumen that coagulates is weighed. ASTM D2397 requires a minimum of 40 % for the cationic rapid-setting grades. It is the defining test of the class, and on a slow-setting certificate the same result would be meaningless.

The consequence is that CRS-2 is a spray grade and nothing else. It is not designed to be mixed with aggregate in a plant, and it will not survive the attempt: put CRS-2 into a pugmill or a concrete mixer and it breaks in the mixer, leaving lumps of coagulated bitumen and free water. The mixing grades are the medium-setting CMS-2 and CMS-2h; the grades that tolerate fine material and cement are the slow-setting CSS-1 and CSS-1h.

2 — the body of the emulsion

The digit is an index of body and binder content. It is not a percentage and not a quality ranking, and reading it as either is the most common misreading of an emulsion designation. Against CRS-1, the number 2 grade buys two things:

• Viscosity. CRS-2 is required to fall between 100 and 400 Saybolt Furol seconds at 50 °C to ASTM D7496; CRS-1 falls between 20 and 100 SFS at the same temperature. A thin emulsion sprayed onto a cambered road runs to the edges and pools in the wheel paths before the chippings arrive, and the seal is rich where it should be lean and bare where it should be rich. The extra body is what holds a sprayed film in position on a crossfall for the seconds that matter.
• Residue. CRS-2 must carry a minimum of 65 % residue by mass by distillation to ASTM D6997, against 60 % for CRS-1. That is the binder you are buying and the binder the seal depends on. On a 14.4 MT container the difference between a 65 % and a 60 % emulsion is about 0.72 MT of binder, before anyone discusses price.

The grades CRS-2 is confused with

• CRS-1 — the same charge and the same setting class, thinner and leaner. It belongs to sand seals and light spray work where a very fast break is wanted from a thinner-bodied emulsion. It is not a substitute for CRS-2 on a chip seal, because thinning the binder film is exactly what a chip seal cannot tolerate.
• RS-2 — the anionic rapid-setting grade under ASTM D977, with negatively charged droplets, an alkaline product, 75–400 SFS at 50 °C, a minimum 63 % residue, a residue penetration band of 100–200 dmm and a demulsibility minimum of 60 % using 0.02 N calcium chloride. It is not a variant of CRS-2; it is the opposite charge. On siliceous stone it has no electrostatic driving force at all and depends far more on the weather. The two must never share a tank, a line or a pump.
• CSS-1h and CMS-2 — the same cationic family, different setting classes and different jobs. CSS-1h is the tack coat and slurry seal grade; CMS-2 is the cold mix grade. Neither will seal a road under chippings.
• CRS-2P and similar — polymer or latex modified versions. ASTM D2397 does not cover modified emulsions, so a CRS-2P is bought against AASHTO M316 or against the agency specification that defines it, and its residue is normally recovered by the low-temperature route in ASTM D7497 rather than by distillation at 260 °C, which degrades the polymer.
• An RS-2 written under IS 8887 — the Indian standard for cationic bitumen emulsions uses RS, MS and SS designations with no C prefix, because every grade in its scope is cationic. An RS-2 on an Indian project document and an RS-2 on an ASTM D977 certificate are opposite charges. Where a grade name arrives without a standard number beside it, ask which standard it is written against before pricing it.

What CRS-2 is not for

• Not a tack coat. A bond coat needs a very light, uniform residual film, which means a slow-setting grade diluted with water. CRS-2 is heavy bodied and cannot be diluted, so it cannot be spread thinly enough or evenly enough. See prime coat vs tack coat.
• Not a prime coat. A prime has to penetrate into a granular base. A rapid-setting emulsion breaks at the surface and bridges it. Emulsion primes use diluted slow-setting grades or purpose-formulated penetrating primes, and on the tightest bases a kerosene-cut cutback still penetrates better.
• Not a mixing grade. Cold plant mix, road mix and stockpile patching are CMS territory.
• Not a material to dilute. Adding water to CRS-2 reduces the residual binder per litre sprayed, and a chip seal short of binder sheds its chippings. Rapid-setting grades are used neat.

Breaking and curing are two different events, and confusing them is what loses a seal

An emulsion works by failing in a controlled way. Breaking is the moment the emulsifier is stripped off the droplets and adsorbed onto the mineral surface, the electrostatic repulsion holding the droplets apart collapses, and the bitumen coalesces into a continuous film. It is visible from the cab: the sprayed film turns from brown to black. Curing or setting is what happens next — water is expelled from the film and evaporates, and the binder develops its cohesion and its bond to the substrate.

Break tells you the emulsion has committed. Cure tells you the pavement is ready. A chip seal can break within seconds and still be nowhere near able to hold chippings against a braking tyre. Most premature chip seal failures are failures to respect that gap: the surface looked black, so the cones came off.

What happens at the stone surface

Granite, quartzite, rhyolite, basaltic and siliceous river and pit gravels — the crushed hard rock most road aggregate is won from — are siliceous. In contact with water the silanol groups at the mineral surface give up protons, and the surface carries a net negative charge across the whole range of pH values encountered on a road job. A CRS-2 droplet carries a positive charge.

Presented to that surface, the droplet is electrostatically attracted to it rather than repelled by it. The amine head of the emulsifier adsorbs onto the mineral, which does two things at once: it anchors the droplet to the stone, and it removes from the water phase the very charge that was keeping the droplets apart. Stripped of their charge, the neighbouring droplets coalesce, first onto the aggregate and then into one another, and within a short time the sprayed film is a continuous bitumen layer keyed to the surface of every chipping standing in it.

This is a chemical break, driven by charge, and its timing is far less dependent on humidity, wind and ambient temperature than an evaporative one. That predictability is the commercial argument for cationic emulsion and the reason nearly every modern national specification is written around it.

Why cationic works where anionic struggles

An anionic emulsion under ASTM D977 carries a negative charge on the droplet. Presented to negatively charged siliceous stone, like meets like and the two repel. There is no chemical driving force pulling the binder onto the aggregate, so the break has to wait for water to leave by evaporation — which makes it a function of the weather forecast rather than of the chemistry. Three things follow, and all three are commercial:

• Speed and predictability. A charge-driven break happens in seconds to minutes on the stone. An evaporation-driven break is slower and much more variable, and on a chip seal that difference decides whether traffic returns the same afternoon or the road stays closed overnight.
• Resistance to stripping. A bond formed by an adsorbed cationic emulsifier survives water far better than a bond that formed only because the water happened to dry out. Stripping is the dominant durability failure of surface treatments in wet climates, which is why the adhesion and anti-stripping question sits behind every emulsion selection.
• Tolerance. Cationic grades also work acceptably on limestone, dolomite and other electropositive stone, so where the aggregate source is not fully known in advance — a normal situation on an export project — CRS-2 is simply the lower-risk purchase. Anionic RS-2 keeps its place where limestone dominates the local supply and where a long-standing specification names it.

Two things the charge argument does not license. A cationic emulsion is not an anti-stripping additive: the chemistry works at the emulsion-to-aggregate interface in a cold-applied operation and does nothing for a hot binder in a hot mix, which is a different problem with a different solution. And charge affinity does not excuse dirty stone. Dust on the chippings defeats a cationic emulsion exactly as reliably as it defeats an anionic one, because the binder then bonds to a dust layer that is itself bonded to nothing.

The window, and why the whole operation is built around it

The practical rule on a chip seal is that the chippings must be down while the binder is still brown. Once the film has begun to turn, the surface of it is coalescing into a skin; a chipping dropped onto a skinned film sits on top of it instead of wetting into it, and the contact area that should have been most of the lower third of the stone becomes a point. That stone will be in the gutter within a week.

Everything in the operation exists to protect that window:

• The chip spreader follows the distributor closely. On a well-run seal the spreader is working within a very short distance of the spray bar, and specifications commonly express the requirement as spreading immediately after spraying rather than as a stated number of seconds. The bar must never out-run the spreader — if the spreader stops, the bar stops.
• Rolling starts immediately and follows the spreader. Pneumatic-tyred rollers press each chipping into the film while it is still mobile enough to flow up around the stone. Rolling after the break embeds nothing; it just polishes the top of the chippings.
• The run length is planned to the truck. A distributor load, a spreader load and a chipping supply that do not match one another produce a gap in the sequence, and the gap always lands on the binder.
• Nobody sprays what cannot be covered. Sprayed binder that cannot be chipped inside the window is a defect to be dealt with, not a section to be caught up on later.

What else breaks the emulsion, and when it is unwelcome

Aggregate is the intended trigger. Several unintended ones will do the same job at the wrong moment:

• Water loss. Evaporation from a thin film on a hot pavement concentrates the emulsion and eventually breaks it with or without stone. On a very hot, dry, windy day the window shortens by itself.
• Fines, cement and dust. Very high surface area material breaks a rapid-setting grade on contact. An unswept surface carrying dust and detritus starts breaking the film the instant it lands, and the binder then bonds to the dust rather than to the road.
• Mechanical shear. A high-shear pump, a cavitating suction line, or a return line discharging above the liquid surface all tear droplets and entrain air. A centrifugal pump run against a closed valve will break a tank of CRS-2 in minutes.
• Freezing. Ice crystals mechanically rupture the emulsifier film around each droplet. The break is permanent and no grade is exempt.
• Contamination with the other charge family, with cutback or with hot binder. Cationic meeting anionic neutralises both charges and coagulates the bitumen on the spot.

Reading the break on site

The colour change from brown to black is the primary field indicator, and it is read across the whole sprayed width rather than at one point, because a run that is breaking unevenly is telling you something about the bar, the temperature or the surface. Two supporting checks are worth knowing. The sweep test to ASTM D7000 is a laboratory method that measures how much aggregate a curing emulsion chip seal sample retains under a brushing action, and it is used to compare emulsions for early chip retention rather than as an ASTM D2397 acceptance requirement. In European practice the Vialit plate shock test to EN 12272-3 serves a comparable purpose for binder–aggregate adhesivity in surface dressing. Neither is a substitute for a trial section with the actual emulsion and the actual stone, which remains the only honest way to find out how a particular consignment behaves on a particular aggregate at the temperature the job will run at.

The chippings are half the seal

The aggregate in a chip seal is not a filler; it is the wearing surface, the skid resistance and the load path. It has to be single-sized, because a graded aggregate produces a layer of variable thickness that no single binder rate can suit — the fines flush and the coarse stone whips off. It has to be low in flakiness, because a flaky chipping lies flat, buries itself in the binder and bleeds. It has to be clean, because dust intercepts the bond. And it has to be dry or only lightly damp: unlike a hot binder, a cationic emulsion tolerates and in some practice benefits from slightly damp stone, and pre-wetting the chippings is used in some markets to help the binder wet the surface — but that is a controlled dampness, not wet stone and not free water.

Average least dimension and the single stone layer

The aggregate spread rate is not chosen by eye. It is set so that the chippings, once rolled, form one stone layer in which the great majority of particles are in contact with the binder and with each other, shoulder to shoulder, standing on their smallest dimension. The controlling geometric property is therefore the average least dimension (ALD) of the aggregate — the average of the smallest dimension of the particles — rather than the nominal sieve size, because it is the least dimension that determines how deep the stone layer will be once it has been rolled down.

Get this wrong in either direction and the seal fails in a predictable way. Too little stone and there is exposed binder between the chippings, which bleeds and picks up. Too much stone and the surplus cannot reach the binder at all: it sits as a loose second course, is swept up or thrown by traffic, and the seal ends up grey and under-stoned where the surplus took chippings with it.

What the design methods calculate, and why this page does not publish a rate

The binder rate is calculated from the same geometry. Once the stone layer depth is known from the ALD, the void space within that layer is known, and the design fixes the residual binder rate as a target proportion of that void space — enough to hold the stone, not so much that it fills the voids and flushes to the surface in hot weather. Published design procedures then apply corrections for the texture of the existing surface (a hungry, coarse surface absorbs binder that a flushed one does not), for traffic volume and speed, for aggregate absorption, and for wastage in spreading.

The procedures in general use include McLeod’s method as published by the Asphalt Institute in the Basic Asphalt Emulsion Manual (MS-19), the design guidance in TRL Road Note 39 for surface dressing in the United Kingdom, and the Austroads sprayed seal design guidance used in Australia and New Zealand. They share the geometry and differ in the correction factors and in the target proportion of voids filled, with figures in the region of seventy percent of the void space commonly quoted for a new seal. That is exactly why this page will not publish a design rate as though it were a specification value: ASTM D2397 does not set an application rate at all, national specifications differ materially, and a rate quoted without its design method and its correction factors is not a rate, it is a number.

Work in residual binder, not in litres

The seal is designed on the binder that stays on the road, and the emulsion is only the vehicle that delivers it. The conversion is straightforward and it should be done before any offer is compared or any quantity is ordered.

Take a CRS-2 at its ASTM D2397 minimum of 65 % residue, with an emulsion density taken as 1.0 kg per litre for the illustration — cationic emulsions typically run in the region of 1.00 to 1.05 kg per litre, a physical property of the product rather than a limit in ASTM D2397, so take the figure for the consignment from the batch certificate or the supplier data sheet rather than assuming it. Sprayed at 1.4 litres per square metre — a mid-band figure taken from typical published chip seal practice and used here purely to demonstrate the calculation, not as a rate for any particular job — that places roughly 0.91 kg of residual binder per square metre. Now suppose the delivered emulsion tests at 60 % residue instead of 65 %. The same 1.4 litres per square metre now places about 0.84 kg, roughly eight percent less binder, and the seal is under-binder at every point on the road. Either the rate is corrected upward or the chippings come off. This is the single most common way a technically compliant delivery produces a failed seal, and it is invisible unless somebody reads the residue line on the certificate and does the arithmetic.

The same arithmetic settles the dilution question permanently. Diluting CRS-2 with water reduces the residual binder per litre in direct proportion, so a diluted rapid-setting emulsion sprayed at the design rate delivers a seal that is short of binder by exactly the dilution ratio. Rapid-setting grades are used neat. Dilution belongs to the slow-setting grades and to the operations — tack coat, fog seal, dust control — where the target residual film is so thin that dilution is the only way to spread it uniformly.

Typical bands, clearly labelled

The table that follows gives the bands that appear in general published practice for planning quantities and for sanity-checking a specification. They are typical practice, not specification requirements, and every one of them is subordinate to the project specification, the design method and a trial section. Use them to work out how many drums to order and to notice when a submitted rate is implausible; do not use them to spray a road.

The trial section is not optional

Two compliant CRS-2 emulsions from two plants can break at noticeably different speeds on the same aggregate, because the designation is a performance envelope rather than a recipe: base binder hardness, emulsifier chemistry and dose, acid dose and final pH, water quality and mill settings are all the manufacturer’s choices within it. Run a trial with the actual emulsion, the actual chippings, the actual spray temperature and the plant that will do the work, read it after traffic has been on it, and record the rate, the temperature and the conditions in the method statement. Re-run it if the aggregate source changes, if a new batch with a different certificate arrives, or if the weather moves substantially.

It must never freeze, and this rule admits no exception

The continuous phase is water. Below 0 °C ice crystals grow through the emulsion and mechanically rupture the emulsifier films around the droplets. The droplets merge, and what thaws is a layer of coagulated bitumen under a layer of dirty water. The change is irreversible. No amount of heating, stirring or recirculation restores it, and there is no cold-climate version of CRS-2 to switch to.

The practical floor is not 0 °C but about 4 °C, and the reason is measurement rather than chemistry: the coldest part of a consignment is never the part anybody measures. The windward drum in a stack, the top of a part-filled tank, the outer container in a stow and the drum standing on cold concrete all run below the bulk temperature. A four-degree margin covers the gap between the thermometer and the worst-off drum. This floor is industry practice and manufacturer guidance, not a requirement of ASTM D2397, which sets no storage temperature at all.

For an export shipment this is a decision taken before the cargo sails, not after it lands. Insulated or heated storage for a winter destination has to be arranged in advance, and emulsion should not be left standing on an open quay in a cold month. Freezing is the single most common way an emulsion shipment is lost, and it usually happens after the material has been accepted.

The upper limit, and how to heat

Above roughly 85 °C water begins to flash off at the surface, a skin forms, the emulsion thickens and eventually it breaks. CRS-2 is one of the heavier-bodied grades formulated to be handled warm, and the storage and working window commonly quoted for it is about 50 to 85 °C — again manufacturer guidance and common practice rather than a requirement of the standard. Confirm the window against the supplier’s technical data sheet for the grade actually delivered; where the two disagree, the data sheet governs.

• Low-intensity, fully submerged coils only. Hot oil or steam. A high coil surface loading boils the water film against the metal, the emulsion breaks locally and cakes onto the heating surface, and the caked layer then insulates the coil so it heats harder still.
• Never heat a tank or drum with an open flame, and never use a bare electric element. This is not only a product-quality rule. Both produce exactly the local overheating described above, and because ASTM D2397 permits the CRS grades to carry up to 3 % petroleum distillate solvent, the vapour space above a warm drum of CRS-2 may be flammable. Bottle burners, torches, brazier fires and open kettles must never be brought to an emulsion drum or tank — a habit carried over from bringing paving-grade drums up to temperature will not announce itself before it goes wrong.
• Circulate gently before applying heat so hot spots cannot develop, and follow the tank builder’s stated maximum coil surface loading. General tank practice is on the bitumen storage tanks page.
• Heat what the day needs. A tank held warm for weeks loses water at the surface, skins, and drifts up the viscosity band with nothing appearing on any delivery note.

Circulate to prevent settlement — and circulate gently

Bitumen droplets are slightly denser than water and drift downward given time, so an emulsion left standing develops a richer bottom and a leaner top. That is what the settlement and storage stability tests to ASTM D6930 predict, and it is why gentle recirculation every few days keeps a stored tank uniform.

The word gentle is doing real work. The same shear that a colloid mill uses to make an emulsion will destroy one:

• Return lines discharge below the liquid surface. A return falling through air entrains it and shears droplets on impact.
• No high-shear or cavitating pumps. A centrifugal pump run against a closed valve will break a tank of CRS-2 in minutes. Positive displacement pumps at modest speed are the normal choice.
• Recirculate, do not agitate violently. The aim is to redistribute a slight density gradient, not to mix a slurry.
• Settlement is recoverable; coagulation is not. If a stored consignment fails settlement but still passes the sieve test, gentle recirculation will usually bring it back. If the sieve result has climbed as well, droplets have already merged and no amount of circulation will undo it.

Do not mix grades in a tank

This rule runs at three levels of severity and all three are worth stating separately, because crews routinely observe the first and ignore the others.

• Never mix cationic with anionic. Combining the two charge families neutralises both and coagulates the bitumen on the spot. This includes pumping one through a line, hose or pump that still holds a film of the other. Changing charge family means flushing every tank, line, pump and hose properly, not rinsing them.
• Do not mix different cationic grades either. CRS-2 and CSS-1h are both cationic, but they are built on different emulsifier systems at different doses to break at completely different speeds. Blending them produces a product that matches neither specification, breaks unpredictably and belongs to no grade a laboratory can test against. A tank is dedicated to one grade, and a part-empty tank is emptied and cleaned before a different grade goes into it — not topped up.
• Never let emulsion meet hot binder or a hot vessel. Water flashing to steam expands more than a thousandfold. Emulsion pumped into a tank, tanker or line still above 100 °C, or onto a residue of hot bitumen, can eject the contents through the hatch. Confirm every receiving vessel is cool, drained and free of hot binder before transfer, and never steam-clean a line into a live emulsion tank.

Storage life, and why the date belongs on the certificate

Neither ASTM D2397 nor ASTM D977 sets a shelf life, and no grade is formulated to last longer than another. What can be said honestly is that emulsion is the one bitumen product family whose properties move measurably while it sits, and that its practical life is weeks to a few months rather than the years a drum of penetration grade bitumen will keep. Every temperature excursion shortens it.

Three practical consequences. Insist that the manufacturing date and batch number appear on the Certificate of Analysis, because a certificate without a date cannot be interpreted. Plan the voyage and the destination storage so the material is used soon after arrival rather than held as buffer stock. And re-run the sieve test to ASTM D6933 at destination before committing an aged consignment to a day’s spraying — it is the quickest and simplest test on the list and it finds coagulum that would otherwise be found by a blocked spray bar in the middle of a run. The product-family view is on the bitumen shelf life and storage page.

Metallurgy, and what a failed sieve test is really telling you

Because the cationic family is acidic, everything the emulsion touches must be mild steel or stainless steel: tank, coil, pipework, pump, valves, hoses, couplings and drums. Aluminium couplings, brass valves, galvanised fittings and zinc-coated pipework corrode, and the dissolved metal ions destabilise the emulsion as they go. The first symptom is therefore often a failed sieve test rather than a visible leak, which makes it easy to blame the supplier for damage the receiving equipment did. Buyers commissioning second-hand tankage for their first emulsion consignment should audit the wetted materials before the cargo arrives.

Health and physical hazards

CRS-2 does not carry the Class 3 flammable liquid case that governs a cutback, but that is a difference of degree in the fire risk and not an exemption from it: the CRS grades are permitted a petroleum distillate fraction and a warm drum of one is not an inert vessel. The rest of the hazard set is routinely underestimated because the product looks like brown paint.

• Chemical burns and eye damage. The product is acidic, typically pH 2 to 4, and the amine emulsifiers are skin irritants and potential sensitisers. Goggles or a face shield, chemical-resistant gloves and long sleeves at every transfer point, and an eyewash within reach of the coupling rather than back at the site office.
• Thermal burns. CRS-2 at 80 °C will scald. Spray temperature is not a warm temperature.
• Steam eruption is the serious physical risk, as set out above.
• A petroleum distillate solvent fraction is permitted, so treat CRS-2 as a material with a flash point until the batch documents prove otherwise. ASTM D2397 allows up to 3 % oil distillate by volume in the CRS grades. That is a light petroleum distillate, not an inert oil, and it partitions into the vapour space of a warm drum or tank. Three rules follow and none of them is satisfied by a general instruction to consult the Safety Data Sheet. First, get the measured flash point for the batch, and read it as what it is: for a solvent-containing bituminous product the flash point is a Tag open-cup figure (ASTM D1310 for liquids generally, ASTM D3143 for cutback asphalts), not the Cleveland open-cup ASTM D92 figure printed on paving-grade certificates. A Cleveland figure quoted against a solvent-containing product overstates the safe temperature and must be challenged, not filed. Second, the material must never be heated with an open flame and never with a bare electric element — indirect low-intensity submerged coils only, hot oil or steam. Third, drums and tanks must be stored away from every ignition source: no smoking, no hot work, no welding, cutting or grinding on or near a vessel that has held the product even if it looks empty, no bitumen kettle or burner alongside an emulsion stack, and bonded and earthed transfer equipment with the bonding verified rather than assumed.
• Spillage must be contained and never flushed to a drain. The emulsion breaks in the drain and deposits bitumen that then has to be dug out.

Shipping and documentation

Bitumen emulsions are commonly not classified as dangerous goods for sea freight, but the classification follows the specific formulation rather than the grade name — confirm it against the Safety Data Sheet for the product you are buying before booking, and be particularly careful where a solvent fraction is present. Beyond the standard export set covered on quality control and export documents, an emulsion order should specify four things on the purchase order: the grade and the standard with its current edition, the tests required on the batch certificate including the five-day settlement result that the standard allows to be waived, the manufacturing date, and the storage conditions at destination, so that the freezing risk and the shelf life are settled before the cargo sails rather than after it arrives.