70号道路石油沥青 · Bitumen 70# for Chinese Highway Projects

70号道路石油沥青是中国用量最大的路面沥青标号。按JTG F40-2004，70号是标称针入度，实际接受范围为60–80（0.1mm），与美标60/70把两个数字当作上下限的写法不同。该标号分A、B、C三个质量等级，针入度相同，等级由蜡含量、10℃延度、针入度指数和老化后残留指标决定，并直接决定可用于哪一等级公路的哪一层次。闪点≥260℃、溶解度≥99.5%，两项均严于ASTM D946。

Bitumen 70# (70号道路石油沥青) is the most widely used paving grade in China. Under JTG F40-2004 the number 70 is a nominal penetration and the acceptance band runs 60–80 (0.1 mm) — not the ASTM convention, where the two numbers in 60/70 are the band limits. The grade is divided into quality classes A, B and C (A级、B级、C级) that share the same penetration band; the class is set by wax content (蜡含量), ductility at 10 °C, penetration index and the residue requirements after ageing, and it determines which highway class and which pavement layer the binder may be used in. Flash point at minimum 260 °C and solubility at minimum 99.5 % are both stricter than ASTM D946, which is why an otherwise compliant 60/70 export cargo does not automatically satisfy a 70# specification.

In the Chinese system, the number carried by a paving grade is the nominal penetration (标称针入度), and the acceptance band is written around it. 70号 — usually written 70# in commercial correspondence — covers a penetration at 25 °C of 60 to 80 tenths of a millimetre, measured under JTG E20 method T 0604 at 100 g load for 5 seconds.

The ASTM convention is the mirror image. Under ASTM D946 the grade name is the band, so 60/70 admits penetration from 60 to 70 dmm and nothing else. Set the two windows side by side and the asymmetry is arithmetic rather than semantic. The 70# window is twenty tenths wide; the 60/70 window is ten, and it sits entirely inside the Chinese one. Every penetration value that passes 60/70 therefore also passes 70#. The converse fails across the upper half of the Chinese window: a batch at 74 dmm sits comfortably mid-grade as 70# and is rejected outright as 60/70.

The commercial reading of that arithmetic is the part worth carrying away. An exporter who treats a 70# enquiry as a 60/70 enquiry has narrowed his own eligible pool on the one property where the Chinese table gave him room to spare, and has left untested the properties where it gave him none. The penetration line is the easiest requirement on the page. It is not where 70# cargoes fail.

道路石油沥青 and the grade family

The material class is 道路石油沥青 (road petroleum asphalt). JTG F40-2004《公路沥青路面施工技术规范》, the Ministry of Transport construction specification for asphalt pavements, defines the family as 160#, 130#, 110#, 90#, 70#, 50# and 30#, each subdivided into quality classes A, B and C. The numbers descend as the binder gets harder, exactly as penetration grading does everywhere else:

• 30# and 50# — hard grades for the hottest, most heavily loaded pavements.
• 70# — the mainstream grade. It carries the bulk of Chinese highway paving because it suits the summer-hot, moderate-winter belt where most of the traffic is.
• 90# — one step softer, used where winters are colder or traffic loading is lighter.
• 110# and 130# — softer still, for cold northern regions and for applications where low-temperature cracking dominates the design.

The second standard: GB/T 15180

The other document a 70# buyer will meet is GB/T 15180《重交通道路石油沥青》, and the difference between the two starts before any number is compared. GB/T 15180 is a national product standard: its job is to say what a heavy-traffic road petroleum asphalt must be, and it names the material AH-70 within a series running AH-130 down to AH-30. JTG F40-2004 is a Ministry of Transport construction specification: its job is to tell a highway contractor how to build an asphalt pavement, and the binder requirement table is one clause inside a much larger works document. One is a product standard; the other is a works specification that happens to contain a product table.

They coincide on the 60–80 penetration band at this consistency and part company on solubility, on the shape of the softening point requirement, on the wax ceiling and on ageing mass change — and only JTG F40 carries the A/B/C classes. Writing 70# / AH-70 into a contract as though the slash meant “or” leaves the acceptance table undecided, which in practice means it will be decided at the destination laboratory, after the cargo has arrived and after the leverage has gone.

Why the naming matters commercially

Three failure modes follow directly from the naming:

• An exporter reads 70# as 60/70 and offers material tested only against ASTM D946. The penetration passes, and the flash point, solubility and wax lines are never checked.
• A buyer converts a 70# specification into 60/70 for the purchase order, then finds the delivered binder rejected at site because the project documents name JTG F40 and a quality class.
• Two parties agree 70# without naming the class. Class is not a preference — it is the property that decides whether the binder may legally be placed in the layer the project needs it for.

The fix is to write the full description into the contract: grade, standard, edition, quality class, and the specific properties the project will test. 70号道路石油沥青，JTG F40-2004，A级 closes far more of the specification than the two characters 70#.

Start from what does not change. A 70# A级 and a 70# C级 are both penetration 60–80, both must reach 100 cm ductility at 15 °C, both must flash at a minimum of 260 °C and both must dissolve to a minimum of 99.5 % — the four lines an export data sheet is most likely to carry are identical across all three classes. A certificate showing those four lines in order proves nothing at all about the class, which is precisely why a class-blind offer looks so convincing on paper.

What changes at 70# is a short list, and it is worth knowing which entries move by how much:

• 蜡含量 wax content — 2.2 % for A级, 3.0 % for B级, 4.5 % for C级, maximum, by the distillation method T 0615. The step from A级 to B级 is a 36 % relaxation on the property that most often decides an import’s fate. Nothing else on the 70# table moves that far between adjacent classes.
• 软化点 softening point — 46 °C, 45 °C and 43 °C minimum. A three-degree spread across the whole class range, which is why softening point is a poor proxy for class even though it is the line most exporters volunteer.
• 10 °C 延度 ductility at 10 °C — the low-temperature cohesion line. It tightens by class and is additionally selected by the climate zone the binder is destined for, so it is the one requirement on this page that cannot be reduced to a single number for 70# without knowing the project.
• 针入度指数 penetration index (PI) — JTG F40 applies a window of -1.5 to +1.0 at 70#, bounding temperature susceptibility in both directions. PI is calculated from penetration measured at more than one temperature, which is why it is almost never present on an export certificate: producing it requires test work nobody ordered.
• 老化后残留指标 post-ageing residue — retained penetration ratio (61 % minimum at 70# A级) and residue ductility, both after RTFOT or TFOT. Mass change is held at ±0.8 % across the classes and is therefore not itself a class separator.

The full class-by-class comparison across every property, and the certificate lines that evidence a class claim, are set out on the dedicated quality class page linked below. The point to take from the 70# view is narrower: at this grade the class is bought and sold on wax and on low-temperature behaviour, and neither of those is visible in a penetration figure.

蜡含量 · Why the wax limit bites hardest at 70#

Wax content is a class gate at every Chinese paving grade, but 70# is where it does the most commercial damage, for a reason that has nothing to do with chemistry. 70# is the mainstream grade. It carries the bulk of Chinese highway paving, so it is the grade an importer is most likely to be asked for, the grade with the largest addressable volume, and therefore the grade against which the largest number of unsuitable cargoes get offered. A wax problem that costs a 130# supplier a niche enquiry costs a 70# supplier the market.

The underlying difficulty is a crude slate difference and there is no point being vague about it. Naphthenic crudes yield bitumen that is naturally low in wax, and binder made from them is the quality benchmark inside China. Many Middle East crudes are more paraffinic and the bitumen made from them is correspondingly higher in wax. ASTM D946 imposes no wax limit whatsoever, so a cargo can be entirely creditable as 60/70, sit comfortably inside the 70# penetration band, and still be 3 % or more on wax — which forecloses A级 outright regardless of how clean the rest of the certificate reads.

Two consequences follow for anyone quoting 70# rather than a specialty grade. First, wax has to be measured to T 0615 on the material actually being offered, before the offer is made; it is not a line to be discovered by a Chinese acceptance laboratory. Second, a measured result above 2.2 % is not a negotiation, it is a redirection — towards the B级 positions where 3.0 % is permitted, or towards a different sourcing route. Reclassifying the same drums does not change the number on the test.

Where each class of 70# is allowed to go

In the Chinese system a class is a permission, not a marketing tier, and the permission is written per highway class (公路等级) and per pavement layer (路面层次). A级 is admitted everywhere — every grade, every layer, every class of highway. B级 is admitted in the lower layers (下面层及以下层次) of expressways (高速公路) and class-1 highways (一级公路), and in every layer of highways below that. C级 is admitted from class-2 highways (二级公路) downwards.

Read that structure with a 70# order in front of you and it produces one question, not two. The question is not what class can you supply; it is which layer of which highway class will this binder be laid in, because the answer to the second determines the acceptable answers to the first. An expressway surface course closes the conversation at A级 immediately. An expressway lower layer or a base course opens B级, and a supplier who cannot reach 2.2 % wax has a genuine position there rather than a lost enquiry. The layer-by-layer matrix is tabulated on the quality class page; confirm the clause wording against the edition of the specification cited in your own project documents, since project approvals can be narrower than the standard permits but never wider.

What an import is actually competing against

One correction to a common sales narrative before the numbers are discussed. China is largely self-sufficient in bitumen from its own refining, and 70# in particular is produced domestically in volume. Import cargo is not covering a national shortage; it works where import logistics beat inland freight into a coastal project, where a price or quality window opens for a period, and where a specific project requires something the nearby domestic supply cannot conveniently deliver. Nobody in China needs to buy an imported 70#.

For a seller that sets the standard of proof. The comparison is not against an abstract specification but against a domestic 70# made from a favourable crude slate and tested to JTG E20 as ordinary routine, whose wax result the buyer has seen a hundred times. An imported offer that arrives with wax unmeasured, PI absent and ductility reported at 25 °C is not a cheaper version of that product; it is an incomplete one. The technical file has to be clean before price becomes a conversation, because price is the only argument that will not survive a failed acceptance test.

Ductility measures how far a moulded specimen of binder can be pulled before the thread breaks, drawn at 5 cm/min in a water bath under JTG E20 method T 0605. What makes it awkward across markets is that the number is meaningless without its temperature, and the three systems do not agree on the temperature.

15 °C · The fixed line, and why 25 °C does not answer it

For 70# the requirement is a minimum of 100 cm at 15 °C. ASTM D946 also asks for 100 cm from a 60/70, but it asks at 25 °C, and Middle East export data sheets almost universally report that figure because that is what their home specification calls for.

The two are not the same test with a cosmetic difference of ten degrees. Bitumen is a viscoelastic material and it stiffens as it cools, so the same binder drawn at 15 °C will reach a shorter thread than at 25 °C — often far shorter. A binder returning a comfortable 100+ cm at 25 °C has been shown nothing about its behaviour at 15 °C; the result simply does not transfer, and no correlation factor is going to be accepted in place of running the test. This is the quietest of the mismatches between an export certificate and a Chinese acceptance table, because unlike wax or PI the line is present on the certificate and looks like it passes. It is the right property, the right unit and the right limit, measured at the wrong temperature.

10 °C · The line this page deliberately does not give a number for

Below the 15 °C requirement sits a second one at 10 °C, and it is one of the properties JTG F40 uses to separate A级 from B级 from C级. It is also selected by the climate zone assigned to the project location, so the applicable limit depends on two variables at once: which class the project specifies, and which zone it sits in. There is no single 10 °C ductility figure for 70#, and any page, data sheet or broker’s table that quotes one has silently chosen a class and a zone on your behalf.

That is why this page states the requirement’s existence and its structure rather than a value. The correct figure is read out of the requirement table in the edition of JTG F40 cited in your own project documents, against your class and your zone code — the three-part code (气候分区) that the design institute assigns from meteorological data, which is set out in full on the climate zone page linked below. Do not let a zone code be inferred from a city name in a supplier’s email; the code belongs to the project location and appears in the project documents.

What this means for a 70# enquiry

A 70# enquiry that arrives with the quality class and the zone code attached can be answered with a specification check. One that arrives with neither can only be answered with a data sheet, and a data sheet is not an answer. The practical sequence for a seller is to obtain both, read the 10 °C limit that actually applies, run T 0605 at both temperatures on the material being offered, and quote the measured values — not the specification range copied across. The residue ductility after RTFOT or TFOT tightens on the same two axes and belongs in the same test order, since it is the least-reported line in the entire Chinese requirement table and the one a Chinese laboratory is most likely to run first.