沥青A级B级C级的区别 · Bitumen Quality Classes A, B and C in China

A级、B级、C级是JTG F40-2004对道路石油沥青的质量等级划分，ASTM和EN没有对应概念。三级针入度完全相同，无法从标号看出等级。区分等级的是蜡含量（2.2%、3.0%、4.5%）、10℃延度、针入度指数和老化后残留指标。等级同时限定适用的公路等级与路面层次，因此合格的70号沥青仍可能因是B级而被A级规格拒收。

A级, B级 and C级 are the quality classes that JTG F40-2004《公路沥青路面施工技术规范》 applies to road petroleum asphalt (道路石油沥青). There is no counterpart in ASTM or EN. The penetration band is identical across all three classes, so the class cannot be read off the grade number — 70# is 60–80 (0.1 mm) in every class. What separates them is wax content (蜡含量), at a maximum of 2.2 %, 3.0 % and 4.5 % respectively, together with ductility at 10 °C (延度), the penetration index (针入度指数) and the requirements on the residue after ageing. The class also fixes permitted use by highway class and pavement layer. The commercial consequence follows directly: a cargo that satisfies every line of the 70# requirement table can still be rejected because it is B级 material offered against an A级 specification, and nothing is wrong with the bitumen.

它不是等级评定，也不是品牌 · It is not a supplier rating

A quality class in JTG F40 is not a commercial tier, not a certification a company holds, and not a description of a refinery. It is an attribute of a specific batch of bitumen, determined by test results on that batch. A supplier does not become an A级 supplier; a particular cargo either meets the A级 limits or it does not, and the next cargo from the same source is assessed again from scratch. Any offer that presents the class as a company credential rather than a batch result has misunderstood the system, and a Chinese buyer will read it that way.

标号与等级是两个独立坐标 · Grade and class are two independent coordinates

Every numbered grade in the JTG F40 series carries the same three-way class subdivision. The standard defines road petroleum asphalt in 160#, 130#, 110#, 90#, 70#, 50# and 30#, and each of those is available as A级, B级 or C级. So 70# B级, 90# A级 and 50# C级 are all valid, complete designations, and 70# on its own is an incomplete one.

Think of it as two axes that do not communicate with each other:

• The grade axis answers how stiff is this binder, and is set by penetration at 25 °C. It is selected from the climate and the traffic loading at the project site.
• The class axis answers how clean, how temperature-stable and how durable is this binder, and is set by wax content, low-temperature ductility, penetration index and the ageing residue block. It is selected from the importance of the position the binder is going into.

Because the two axes are independent, no amount of information about one tells you anything about the other. This is the single sentence to take away: the class cannot be read off the grade number. A trader who receives an enquiry for 70# and quotes 70# has answered half the question, and it is not obvious from the reply which half.

等级是一种许可 · The class is a permission, not a preference

The most useful way to hold the concept is that JTG F40 does not merely describe the three classes — it states what each one is allowed to be used for, by highway class (公路等级) and by pavement layer (路面层次). A级 is permitted for all grades and all pavement layers on every class of highway. B级 is permitted for the lower layers of expressways (高速公路) and class-1 highways (一级公路), and for all layers of highways of lower class. C级 is for class-2 highways (二级公路) and below.

Holding the concept that way reorders the whole enquiry. A permission is attached to a position in a road, not to a cargo in a tank, so the specification is derived by working outward from the position: the layer fixes the class, the class fixes which set of limits applies, and only then does the grade number acquire a meaning that can be checked. An enquiry that opens by naming a class has skipped the derivation and is asserting a conclusion. An enquiry that opens by naming the highway class and the layer can be worked through against the standard by either party independently, and arriving at the same answer separately is what makes the resulting offer defensible rather than merely agreed.

最弱一项决定等级 · A cargo takes the class of its weakest line

The class is not awarded on balance or on average. Every class-linked property has to meet the limit for the class being claimed, and the lowest line governs the outcome. Take a 70# that clears the A级 wax limit with room to spare and satisfies both ductility lines, then returns a retained penetration ratio of 58 % on the aged residue against the 61 % floor that A级 applies at 70#. That cargo does not carry the A级 permission at all, and the observation that every other line passed has no standing in an acceptance clause. There is no partial credit and no offsetting of a strong line against a weak one, and a certificate that quietly leaves the weak line off the page does not change the outcome — it moves the discovery to the destination laboratory.

GB/T 15180 没有等级 · The second standard has no classes at all

This is a specific trap worth naming, because it appears in real enquiries, and the reason it exists is that the two documents are different kinds of object. JTG F40-2004《公路沥青路面施工技术规范》 is an industry standard (行业标准) issued by the transport ministry, and it governs how an asphalt pavement is built. The class system lives inside it precisely because that document is concerned with what goes into a particular layer of a particular road. GB/T 15180《重交通道路石油沥青》 is a national product standard (国家标准) for heavy-traffic road petroleum asphalt, and it describes the material without reference to where it will be laid — so there is nothing for a permission to attach to. That is the whole reason one carries classes and the other does not. GB/T 15180 grades the same material with AH- designations — AH-130, AH-110, AH-90, AH-70, AH-50, AH-30 — and carries no A/B/C class structure whatsoever. It has one limit set per designation.

Consequently, a request for AH-70 A级 is asking for something that does not exist. It usually means one of two things: the buyer wants AH-70 to GB/T 15180 and has added the class out of habit, or the buyer actually wants 70# A级 to JTG F40 and has picked up the AH designation from a domestic price report. Those are different specifications with different limits on solubility, softening point, wax content and post-ageing mass change. The gap has to be closed before pricing, not after loading, and the way to close it is to ask which document the project will be accepted against.

为什么西方规格里没有这个概念 · Why ASTM and EN have no equivalent

ASTM D946 and EN 12591 both control consistency and, to a degree, ageing, and they leave purity and temperature susceptibility largely to the market and to the specifying engineer. Neither sets a wax content limit at all. Chinese practice took the opposite route: it wrote purity and durability into the acceptance table, then tied the resulting classes to permitted use so that the most demanding positions in the network are reserved for the cleanest material. Whether that is the better approach is not the point. The point is that a specification written in one system carries no information about the other, and an exporter cannot infer a class from an ASTM certificate — the properties that decide the class were never measured.

针入度为什么不参与分级 · Why penetration is excluded

Penetration is a single measurement at a single temperature. A needle under 100 g sinks into a conditioned sample for five seconds at 25 °C, and the depth in tenths of a millimetre is the result. It is an excellent way to sort binders by stiffness, which is exactly what a grade designation is for. It is a poor way to sort them by anything else.

Two binders with identical penetration can differ in how much crystalline wax they carry, in how sharply they stiffen when the pavement drops to −10 °C, in how fast they harden in the mixing plant, and in how well they stick to the aggregate. None of those differences show up at 25 °C on a penetration bench. The Chinese class system exists precisely to catch what penetration misses, which is why using penetration to set the class would defeat the purpose of having classes. Hence the design: one penetration band, three classes inside it.

蜡含量 · Wax content — the property doing most of the work

Wax is the class gate in practice, and the limits are unambiguous: maximum 2.2 % for A级, 3.0 % for B级 and 4.5 % for C级, determined by the distillation method under JTG E20 method T 0615. Note that these figures do not change with the grade. A 30# and a 130# face the same wax limit for the same class, which tells you how the standard views the property — as a purity criterion rather than a performance trade-off.

Why the standard hung the class on this property rather than another is worth one paragraph, because it is not self-evident. Wax works against the pavement at both ends of the service range at once — rigid filler when the road needs to relax stress in the cold, low-viscosity diluent when it needs to resist deformation in the heat — and it concentrates in the few micrometres of binder that actually touch the aggregate. One measurement therefore anticipates several failure modes that otherwise look unrelated, which is precisely what a permission system needs: a single number capable of separating material fit for the most exposed positions in the network from material that is not. The mechanisms in detail belong to the wax content page. What matters for the class is that none of them registers on a penetration bench or a ring-and-ball apparatus, so the class had to be attached to something the consistency block could not already see.

The supply-side consequence has to be stated plainly rather than managed around, because it decides which classes a given exporter can realistically quote at all. Wax arrives with the crude and survives into the vacuum residue. It is not created by carelessness at the plant and it is not removed by diligence there, so quality control does not move the number. Chinese domestic production has historically run naphthenic crude slates, which yield naturally low-wax binder, and the requirement tables were calibrated against that material — the 2.2 % figure describes the domestic benchmark rather than an arbitrary target. Many Middle East crudes are appreciably more paraffinic and the bitumen they yield carries more wax accordingly. The practical result is that a cargo which is entirely respectable under ASTM D946, a specification containing no wax line at all, may have no route to A级 at any price, from any supplier, however well the rest of the table reads. That is the largest single technical barrier between Middle East supply and a Chinese project specification. The response that works is to establish the T 0615 figure first and choose which class to quote from it, rather than quoting a class and finding the figure afterwards.

10 ℃ 延度 · Ductility at 10 °C — the low-temperature line

Ductility stretches a briquette of bitumen at 5 cm/min until it breaks and records the elongation. It measures cohesion and the capacity to accommodate movement without brittle fracture. The class-separating version of this test is not the general one — JTG F40 sets a broad requirement of minimum 100 cm at 15 °C for 70# and 90#, and then applies a further requirement at 10 °C whose limit tightens with the class and moves again with the climate zone.

The trap for an exporter is the test temperature. A typical Middle East export data sheet reports ductility at 25 °C, where almost any sound paving binder reaches 100 cm without difficulty. That result carries no information about behaviour at 15 °C and none at all about 10 °C, because ductility falls away non-linearly as the binder cools and the point at which it collapses varies enormously between binders of the same penetration. Passing at 25 °C is not evidence of anything the Chinese table asks about, and treating it as evidence is how cargoes end up being tested for the first time at the destination.

针入度指数 PI · Penetration index — temperature susceptibility

PI is calculated rather than measured directly, from penetration values obtained at more than one temperature. It condenses into a single number how sharply the binder changes consistency as the temperature moves. A strongly negative PI describes a binder that softens rapidly as it warms and stiffens rapidly as it cools — the behaviour a pavement can least tolerate, because it fails at both ends of the service range rather than one. JTG F40 applies a window of -1.5 to +1.0 at 70#, and the applicable window should be read from the requirement table for the grade and class in hand.

PI matters to this page for a practical reason as much as a technical one: it appears on almost no Middle East technical data sheet. Producing it requires running penetration at additional temperatures, which most export laboratories do not do as routine. An offer that cannot report PI is an offer with a class-linked property left blank, and the engineer reviewing it knows that.

老化后残留指标 · The ageing residue block — the durability half

The rolling thin film oven test (T 0610) and the thin film oven test (T 0609) subject a film of binder to heat and air movement to simulate the oxidation and volatile loss that occur during plant mixing. Three things are then measured on what remains:

• 质量变化 mass change, limited to ±0.8 %. This line is common across the classes rather than class-separating, but it is the entry point to the block and a cargo that fails it fails everything downstream.
• 残留针入度比 retained penetration ratio — how much of the original penetration survives, expressed as a percentage. The A级 floors descend as the binder softens: 63 % at 50#, 61 % at 70#, 57 % at 90#, 54 % at 110#. A binder that hardens sharply in the plant reaches the road already part-aged.
• 残留延度 residue ductility — the ductility of the aged residue, which tightens by class and again by climate zone. This is the most demanding line in the block and the one most often absent from an export certificate.

The ageing block is where the class system does its least visible and most valuable work. Every failure it predicts appears years after handover, as transverse cracking in the third or fourth winter, at which point no one is testing binder any more. Reserving the tightest residue requirements for A级, and reserving A级 for the surface course of the highest-class highways, is a coherent piece of engineering policy rather than bureaucratic layering.

四项的共同点 · What the four have in common

Wax content describes purity. Ductility at 10 °C describes low-temperature behaviour. PI describes temperature susceptibility across the range. The residue block describes durability under processing. None of them is a consistency measurement, and that is the design. The grade number answers what is this binder; the class answers how long will it keep being that, and how cleanly. Which is why the two can never be collapsed into one number, and why an enquiry that names only the grade has left the more consequential half unanswered.

情景 · A worked illustration

Take an entirely ordinary and hypothetical set of results on a cargo built to a Middle East export specification and tested against the Chinese table. Penetration at 25 °C comes back at 68 (0.1 mm) — inside the 60–80 band for 70#, with margin at both ends. Softening point 48 °C, above the 46 °C floor for A级. Flash point 268 °C, clearing the 260 °C requirement. Solubility 99.6 %, clearing the 99.5 % line. Ductility at 15 °C over 100 cm. Mass change after RTFOT well inside ±0.8 %. Retained penetration ratio 64 %, above the 61 % floor.

By any reading, this is sound paving bitumen and it is unambiguously 70#. Then the wax content comes back at 2.9 % by T 0615. The cargo is 70# B级. The project is the surface course of an expressway, specified as 70# A级. The cargo is rejected, and the rejection is correct.

Notice what has and has not happened. Nothing is wrong with the bitumen. It has not degraded, it has not been contaminated, it has not been misdescribed as to grade, and it would perform well in a great many pavements — including the lower layers of the very expressway that just rejected it. It fails on one property, by seven-tenths of a percentage point, against a limit that the specification it was manufactured to does not contain.

损失落在谁身上 · Where the loss actually lands

That depends entirely on what the contract said, and the two common versions produce opposite outcomes.

• If the contract says “Bitumen 70#” and nothing more, the seller has arguably delivered conforming goods. The material is 70#. The buyer holds a cargo it cannot use in the position it was bought for, and a weak claim. This is the more common version, and it is the more expensive one for the buyer.
• If the contract says “70号道路石油沥青，JTG F40-2004，A级”, the seller has delivered non-conforming goods and the exposure sits with the seller — rejection, re-testing costs, demurrage, storage at destination, and the cost of finding a home for material that is now sitting in the wrong country.

Neither outcome is good, and both were avoidable at the point the enquiry was written. The class is not a detail to be settled later in the negotiation; it is one of the two coordinates that identify the product.

为什么发现得太晚 · Why it surfaces late, every time

The failure has a structural reason for being discovered at the destination rather than at the load port. Wax content is not on an ASTM D946 technical data sheet, because ASTM does not require it. Penetration index and 60 °C dynamic viscosity are usually not there either. So the properties that decide the class are precisely the properties that the exporting laboratory has no routine reason to measure and the exporting sales team has no number to quote. Everyone looks at the lines they can see, all of which pass, and the class-deciding lines stay invisible until a Chinese acceptance laboratory runs T 0615 on material that has already sailed.

The fix is unglamorous and completely reliable: test the class-linked properties before offering, not after arriving. A wax content determination is a small cost set against a container of cargo in the wrong hemisphere.

B级货怎么办 · What to do with B级 material — the constructive answer

Being B级 is not a defect and it does not make a cargo unsellable. It makes it unsellable into an A级 position. The permitted-use table above is also a market map read the other way round:

• Lower layers of expressways and class-1 highways — by tonnage the larger part of the binder in the structure, because the layers beneath the surface course are thicker and there are more of them.
• All layers of class-2 highways and below, where B级 is permitted throughout.
• Applications governed by their own provisions rather than the class-and-layer split, which should be read from the standard rather than assumed.

Declaring the ceiling is the commercially stronger move as well as the more honest one, and the reason is mechanical rather than moral. A buyer handed the class-linked results and the permitted positions that follow from them can place the cargo straight away and can defend the placement internally. A buyer handed an unsupported A级 claim has to verify it, and the verification is the event that produces the rejection. The first version transacts. The second version transacts once.

反向的错误：规格开高了 · The mirror-image mistake — over-specifying

The error runs both ways, and the second version is quieter because nobody ever gets rejected for it. A buyer procuring binder for the lower layers of a class-2 county road writes A级 into the purchase specification, because A级 is the best and the template said so. The result is a narrower supply pool, a higher price and a longer lead time, in exchange for durability margin that the position does not require and the pavement will never use.

This is why the layer question matters more than the class question. Ask what the binder is going into, establish the class the standard actually requires for that position, and specify that. Specifying above requirement is not conservative procurement; it is paying for a permission you are not going to exercise.

把它写进合同 · The contract wording that closes the gap

The description that removes the ambiguity is short. It names the grade, the standard, the edition, the class, the test protocol and the inspection arrangement in one line: 70号道路石油沥青，JTG F40-2004，A级；试验按 JTG E20-2011；装港由独立检验机构检验，留样封存双方各持一份 — 70# road petroleum asphalt to JTG F40-2004, class A, tested to JTG E20-2011, with independent inspection at load port and sealed retained samples held by both parties.

Compare that with “Bitumen 70# or equivalent”. The second version leaves the class undefined, the standard undefined, the test protocol undefined and the dispute mechanism undefined, and the word equivalent does no work at all in a system where the class-deciding properties are absent from the other standard entirely.

争议怎么处理 · Handling the dispute if it happens anyway

Three things determine whether a class dispute can be resolved or only argued about. Traceable sampling — samples drawn across the cargo rather than from one drum at the container door, sealed in the presence of an independent inspector, with a set held by each party. A test result means nothing if the sample behind it cannot be tied to the shipment. Method traceability — the certificate should print the JTG E20 method number against each line, because a result produced under an ASTM procedure invites the question of whether T 0615 or T 0605 would have returned the same figure, and on a marginal line that question is not academic. Batch specificity — a certificate showing measured values for the batch that actually shipped, not the specification range copied across. A certificate whose numbers land exactly on the specification limits every time is a document that will not survive scrutiny at the moment it is most needed.