.png?imageMogr2/crop/220x71/gravity/center/format/webp)
Highway and expressway project buyers rarely get a second chance at the binder specification. Once the paving season starts, a binder that cannot hold up under heavy axle loads and high pavement temperatures turns into rutting, raveling, and early-life rehabilitation that costs far more than the material saved on paper. This guide is written for contractors, design institutes, and government project buyers who need to evaluate polymer modified asphalt for highway construction before committing to a supplier — with the performance-grade logic, the test data, and the supply questions that should all be settled before the first tanker is scheduled.
What PG Grading Actually Tells You Before You Buy
Performance Grade (PG) grading is the Superpave binder classification system defined under ASTM D6373 and AASHTO M 320. A PG grade is written as two numbers: the first is the high pavement temperature the binder can resist rutting at, and the second is the low temperature it can resist thermal cracking to. A binder graded PG 76-22, for example, is expected to perform at pavement temperatures up to 76°C and down to -22°C.
The high-temperature end of the grade is measured with a Dynamic Shear Rheometer (DSR) using the rutting parameter G*/sinδ, per AASHTO T315. The higher this value at the target temperature, the stiffer the binder resists permanent deformation under repeated loading. For polymer modified asphalt, this is the single most informative number a buyer can ask for — modification is supposed to raise exactly this parameter.
In practice, many asphalt suppliers quote only penetration grades (such as 60/70 or 40/50), which are measured under ASTM D5 and describe consistency at 25°C rather than in-service temperature behavior. Penetration grading is not wrong — it is the standard contract language in much of Asia, the Middle East, and Africa — but a buyer specifying a polymer modified binder for a heavy-traffic expressway should always ask two questions: what is the DSR data at the design pavement temperature, and what are the TFOT/RTFOT residual properties after short-term aging? A supplier who can produce both, method by method, is a supplier whose data you can build a pavement design on.
As a concrete reference point, Chambroad's 40/50 paving grade publishes a DSR value of G*/sinδ = 1.06 kPa at 70°C (limit ≥ 1.0 kPa, AASHTO T315) directly on its product specification page. When you compare suppliers, look for that level of method transparency — not just a product name with "modified" attached to it.
The Failure Modes Your Binder Specification Must Resist
Before comparing grades, be clear about which distresses the project actually needs to defend against. On highway and expressway pavements, four drive most binder decisions:
- Rutting resistance — permanent deformation in the wheel paths at high pavement temperatures, driven by heavy traffic and slow-moving or standing loads on climbs and intersections. This is the primary target of polymer modification.
- Thermal cracking resistance — transverse cracks that initiate when the binder stiffens beyond its low-temperature grade in cold seasons.
- Fatigue resistance — alligator cracking under millions of moderate load repetitions over the design life, governed by the binder's intermediate-temperature behavior.
- Aging and durability — oxidation and volatilization during mixing, hauling, and service, measured as retained penetration and retained ductility after TFOT aging.
A polymer modified asphalt for expressway projects should improve the first and fourth of these without sacrificing workability. When you review supplier data, check the after-aging columns as carefully as the fresh values: a binder with excellent virgin properties but a residual penetration ratio below specification will not deliver the long service life the design assumed.
Penetration Grades vs Modified Grades: Which Base to Specify
Unmodified penetration-grade binders remain the workhorse of highway construction, and the choice between 60/70 and 40/50 already shapes high-temperature performance. The table below consolidates the published quality data for Chambroad's two paving grades — every value with its test method is also visible on the 60/70 product page and the 40/50 product page:
| Property | Method | 60/70 (typical) | 40/50 (typical) |
|---|---|---|---|
| Penetration, 25°C, 100 g, 5 s | ASTM D5 | 67 (spec 63–68) 0.1 mm | 44 (spec 40–50) 0.1 mm |
| Softening point (R&B) | ASTM D36 | 48.0°C (spec ≥ 48°C) | 51.5°C (spec 48–58°C) |
| Ductility, 25°C | ASTM D113 | >100 cm (spec ≥ 100) | >100 cm (spec ≥ 100) |
| Flash point (COC) | ASTM D92 | 274°C (spec ≥ 260°C) | 268°C (spec ≥ 232°C) |
| Solubility in trichloroethylene | ASTM D2042 | 99.89% (spec ≥ 99.5%) | 99.92% (spec ≥ 99.0%) |
| Dynamic viscosity, 60°C | ASTM D2171 | 239 Pa·s (spec ≥ 180) | — |
| DSR, G*/sinδ at 70°C | AASHTO T315 | — | 1.06 kPa (spec ≥ 1.0) |
| Wax content (distillation) | DIN 52015 | 0.8% (spec ≤ 2.0%) | — |
| Mass change after TFOT | ASTM D1754 | -0.165% (spec ± 0.5%) | -0.233% (spec ≤ 0.8%) |
| Residual penetration ratio, 25°C | ASTM D5 | 93.5% (spec ≥ 75%) | 68% (spec ≥ 58%) |
| Residual ductility, 25°C (TFOT) | ASTM D113 | >100 cm (spec ≥ 50) | >100 cm (spec ≥ 48) |
| Density, 15°C | ASTM D70 | 1.034 g/cm³ | 1.036 g/cm³ |
How to read this as a buyer: the 40/50 grade is the harder, higher-softening-point binder of the two. It is the natural base for hot climates, steep grades, slow traffic corridors, and as the feedstock for high-modulus and polymer-modified products, where its 70°C DSR value is already on specification before any modification. The 60/70 grade offers the deeper ductility reserve and the stronger after-aging retention (93.5% residual penetration ratio), which suits moderate climates and high-volume general-purpose carriageways. Specifying a stiffer base than the traffic demands buys nothing; specifying a softer one where rutting governs costs a rehabilitation cycle.
If your project's tender references an international specification or a national road standard built on PG terminology, send the clause list to the supplier before sampling and ask them to map their published data to each required parameter — including which values are measured per lot and which are design limits. That single exchange usually reveals how production-ready a supplier actually is.
How Modification Changes the Game: SBS and High-Modulus Routes
Where unmodified binders reach their limit — intersections, bus lanes, airport runways, long tunnels, and full-depth pavement structures — modification takes over. The two routes buyers encounter most often are:
- SBS-modified asphalt, where styrene-butadiene-styrene copolymer is dispersed into the binder to raise the high-temperature grade, improve elastic recovery, and widen the working temperature window. It is the default answer for rutting resistance on heavily loaded expressway lanes.
- High-modulus durable asphalt, which stiffens the asphalt layer itself so the pavement structure can be built thinner without losing load capacity — a structural redesign rather than a simple grade bump.
Both routes are proven at project scale. On the Zhanlin Expressway in Shandong Province, Chambroad's durable high-modulus modified asphalt was used with Shandong Expressway and the Shandong Jiaotong Science and Technology Institute to lay a full-thickness durable asphalt pavement demonstration section — a structure 39 cm thinner overall than the traditional combined-base design, at essentially the same construction-period investment, with advantages in energy saving, service life, and whole-life-cycle cost. The full case is published on the Zhanlin Expressway project page.
Enclosed environments add a different requirement: worker safety and emissions during paving. On the 6.15 km Chunmushan Tunnel of the Zhitong Expressway in Hunan Province — the longest tunnel in the province's expressway network under construction — a low-carbon, odorless modified asphalt reduced H₂S emissions by 65% and VOCs by 60% during construction, without changing binder performance or the paving process. The Chunmushan Tunnel project page documents both figures. If your project includes long tunnels or urban segments with restricted working windows, emissions performance belongs in the technical comparison alongside the mechanical properties.
For buyers assembling a tender shortlist: contact the Chambroad asphalt team with your project climate zone, traffic category, and target structure, and ask which base grade and modification route the published data supports.
Test Documents to Request Before Bulk Ordering
Specification sheets are the start of the conversation, not the end. Before releasing a bulk order for a highway project, request the following from any shortlisted supplier — and file all of it with the bid package:
- Certificate of Analysis for the actual production lot, with measured values (not specification limits) for penetration, softening point, ductility, flash point, and solubility.
- Aging data: TFOT or RTFOT mass change, residual penetration ratio, and residual ductility, with test methods stated.
- DSR data (G*/sinδ) at the design pavement temperature for modified grades, per AASHTO T315.
- Wax content and density, which affect both low-temperature behavior and mix design volumetrics.
- For polymer modified products: modification type, polymer content, and storage/handling requirements (storage temperature, agitation, allowable hold time) so the paving crew can plan plant operations.
- Trial-batch or test-section references where the same grade has been paved under comparable traffic and climate.
A supplier who produces these documents as a matter of routine — with methods traceable to ASTM, AASHTO, or the national standard your tender cites — is demonstrating process control, not just marketing. Chambroad publishes 100% pre-shipment testing practice for its material lines, and the asphalt product pages above carry the measured values behind every specification limit; hold any supplier you evaluate to the same standard.
Supply and Export: What to Confirm About Delivery
Technical qualification and logistics qualification should run in parallel. For government and municipal projects, delivery certainty is part of the specification: a binder that arrives late forces the paving window into the wrong season. Points to settle in writing before award:
- Production capacity and current commitments across the project's paving window, not just annual tonnage.
- Packaging and transport format — bulk tanker, drum, or jumbo bag — and which formats your plant can receive.
- Export documentation experience if the project is outside the producing country; cross-border supply chains reward suppliers who have done it before. Chambroad asphalt has shipped into Southeast Asian infrastructure markets, as documented in the ASEAN export report.
- Technical support during paving: lab-to-site communication channels for adjusting the mix design if field conditions deviate from the trial section.
A Pre-Order Checklist for Highway Project Buyers
Condensing this guide into the sequence we recommend before any purchase order is issued:
- Step 1 — Define the governing distress. Rutting, cracking, fatigue, or emissions: rank them for your climate zone and traffic category.
- Step 2 — Fix the base grade. Use the penetration data and DSR values above to decide 60/70 vs 40/50 as the base, or go straight to a modified product if the structure demands it.
- Step 3 — Collect lot-level test documents for every shortlisted supplier, with methods, not just limits.
- Step 4 — Verify at project scale. Trial section or reference project under comparable conditions, documented.
- Step 5 — Lock logistics and support terms across the paving window before signing.
If you are preparing a bid or a technical comparison for an upcoming highway, expressway, airport, or municipal project, the Chambroad team can supply the specification documents behind the data in this guide and confirm availability for your paving schedule.
Planning a highway or expressway project and need binder data you can defend in a tender?
Get the full specification package, lot-level test reports, and a supply proposal for your paving window.
Contact Our Asphalt Team
