How To Blown Asphalt
Last updated: 2026-10-15
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How To Blown Asphalt
Blown asphalt (industrial asphalt, oxidized bitumen) is produced by passing air through hot bitumen at 240–270°C for 6–12 hours, which raises its softening point from ~45°C to 95–115°C and lowers penetration to 10–30 dmm (0.1 mm). Typical batch sizes run 20–100 tonnes per reactor, and air is injected at 40–120 m³/hour per tonne of bitumen. The process consumes 15–30 kWh of electricity per tonne plus 8–15 m³ of fuel gas per tonne for heating, giving a finished blown asphalt price of roughly $480–$650 per tonne FOB depending on grade and region.
What Is Blown Asphalt and How It Differs From Penetration-Grade Bitumen
Blown asphalt is normal bitumen that has been oxidized — chemically cross-linked by blowing air through it at high temperature. Penetration-grade bitumen (e.g., 60/70, 80/100) is the starting material; blown asphalt is the transformed product.
| Parameter | Penetration Grade 60/70 | Blown Asphalt (Type III) | Blown Asphalt (Type IV) |
|---|---|---|---|
| Softening point (°C) | 49–56 | 90–100 | 105–115 |
| Penetration @25°C (dmm) | 60–70 | 20–30 | 10–20 |
| Flash point (°C) | ≥230 | ≥250 | ≥260 |
| Solubility in TCE (%) | ≥99 | ≥99 | ≥99 |
| Density @25°C (kg/m³) | 1010–1030 | 1030–1050 | 1040–1060 |
| Application | Roads | Roofing, waterproofing | Pipe coating, mastics |
Key differences in practice:
- Hardness — blown asphalt is 2–4× harder than paving grade, measured by lower penetration.
- Temperature resistance — it will not soften or flow at roof surface temperatures up to 90–100°C.
- Ductility — drops from >100 cm (paving grade) to 2–10 cm, which is acceptable for waterproofing but disqualifying for road mixes.
- Price — blown asphalt trades at roughly $40–$90 per tonne above penetration grade, reflecting processing cost.
The Blown Asphalt Production Process Step by Step
The industrial oxidation process follows a fixed sequence. Small plants run 1–3 reactors; large exporters in Iran, China, and South Korea run 4–8 reactors with a combined output of 300–800 tonnes/day.
1. Feedstock selection and preheating (1–2 hours)
- Use bitumen with penetration 60/70 to 80/100. A lower penetration feedstock shortens blowing time by 15–25%.
- Charge 20–100 tonnes into the reactor and heat to 200–220°C using a hot-oil coil or direct gas burner.
- Feedstock cost: $350–$480/tonne, representing 70–80% of total production cost.
2. Air injection and oxidation (6–12 hours)
- Inject compressed air through a sparger ring at 40–120 m³/hour/tonne at 1.5–3.5 bar.
- Maintain reactor temperature between 240°C and 270°C. Below 240°C, reaction time doubles; above 280°C, cracking and flash-fire risk rise sharply.
- Exothermic reaction: the air blowing itself generates 30–40% of the heat required, so burner load drops as the reaction progresses.
3. Monitoring and cut-off (continuous)
- Test softening point (ring & ball), penetration, and viscosity every 30–60 minutes.
- Stop when the target softening point is reached. Overshooting by 10°C wastes 1.5–2 hours and $6–$10/tonne in fuel.
4. Finishing (0.5–1 hour)
- Degas, add filler or polymer modifier if required, then cool to 160–180°C for loading into drums, tankers, or kraft paper bags.
| Production Step | Duration | Temp Range | Energy Use per Tonne |
|---|---|---|---|
| Preheating | 1–2 h | 200–220°C | 3–5 m³ gas |
| Air blowing | 6–12 h | 240–270°C | 5–10 m³ gas + 15–30 kWh |
| Finishing/loading | 0.5–1 h | 160–180°C | 1–2 m³ gas |
| Total | 8–15 h | — | 9–17 m³ gas + 15–30 kWh |
How To Blown Asphalt: Critical Process Variables and Specifications
Five variables determine product quality and cost. Get any one wrong and you either miss specs or waste money.
1. Air rate and air-to-bitumen ratio. The standard is 40–120 m³/h per tonne. Doubling the air rate can cut blowing time by up to 30% but risks localized overheating and higher asphalt hardening. Pilot trials before scaling.
2. Reactor temperature. Hold 240–270°C. Every 10°C above 270°C shortens reaction time by roughly 8% but increases cracking by 20–30%, degrading solubility.
3. Feedstock penetration. Starting at 60/70 instead of 80/100 saves approximately 1.5 hours of blowing time per batch — worth about $8–$12 per tonne.
4. Catalyst use. Ferric chloride (FeCl₃) at 0.1–0.5% by weight cuts blowing time by 20–40%. Cost: about $2–$6/tonne of product. Most export-oriented plants use it.
5. Batch vs. continuous. Batch reactors dominate below 500 tonnes/day. Continuous plants achieve 5–10% lower unit energy costs but need stable feedstock and $2–5 million more capex.
| Variable | Typical Range | Effect on Time | Effect on Cost/Tonne |
|---|---|---|---|
| Air rate | 40–120 m³/h/t | −30% at max | +$1–3 |
| Temperature | 240–270°C | −8% per +10°C | −$2–4 |
| Feedstock pen. | 60/70 vs 80/100 | −1.5 h | −$8–12 |
| FeCl₃ catalyst | 0.1–0.5% | −20–40% | +$2–6 |
| Batch vs continuous | — | −10% | −$5–10 |
Blown Asphalt Grades, Applications, and Market Prices
Blown asphalt is graded by softening point. Buyers typically specify per ASTM D312 (Types I–IV) or EN 13304/13305.
| Grade | Softening Point (°C) | Penetration (dmm) | Main Application | Price FOB ($/tonne) |
|---|---|---|---|---|
| Type I | 85–95 | 30–40 | Roofing felt saturant | 480–520 |
| Type II | 95–105 | 20–30 | Built-up roofing | 500–550 |
| Type III | 105–115 | 10–20 | Waterproofing membranes | 530–590 |
| Type IV | 115–125 | 5–15 | Pipe coating, mastics | 560–650 |
Application notes:
- Roofing (60–65% of global demand) — Type I and II, sold in 25 kg or 50 kg bags or bulk tankers.
- Waterproofing membranes (20–25%) — Type III, often modified with 10–15% SBS or APP polymer.
- Pipe coating and mastics (10–15%) — Type IV, requires softening points above 115°C.
- Export logistics — bulk shipments in 20–25 tonne ISO tanks or 150–180 kg steel drums. Drummed product adds $40–$70/tonne in packaging and freight.
Quality Control Checklist for Blown Asphalt
Before certifying a batch, run these tests. A single failed parameter can mean a $3,000–$8,000 rejected container.
- Softening point (ASTM D36) — must fall within ±5°C of the target grade.
- Penetration @25°C (ASTM D5) — ±3 dmm tolerance.
- Flash point (ASTM D92) — minimum 250°C for shipping safety.
- Solubility in trichloroethylene (ASTM D2042) — minimum 99%; below this signals over-blowing.
- Loss on heating (ASTM D6) — maximum 1% at 163°C.
- Stain test (ASTM D2746) — must pass for roofing grades to prevent oil bleed.
Typical rejection causes and their frequency in export lots:
| Defect | Frequency | Root Cause | Cost Impact |
|---|---|---|---|
| Low softening point | 35% | Under-blowing | $3,000–5,000/container |
| High penetration | 25% | Excess air, low temp | $3,000–5,000/container |
| Low solubility | 20% | Overheating >280°C | $5,000–8,000/container |
| High loss on heating | 12% | Volatile feedstock | $2,000–4,000/container |
| Stain test failure | 8% | Poor feedstock quality | $3,000–6,000/container |
FAQ: How To Blown Asphalt
How long does it take to blow asphalt?
Standard oxidation runs 6–12 hours per batch at 240–270°C. With FeCl₃ catalyst at 0.1–0.5%, time drops to 4–8 hours. Higher softening-point grades (Type IV) sit at the top of the range.
What temperature is used for blown asphalt production?
The reactor is held at 240–270°C. Below 240°C the reaction slows by 50% or more; above 280°C you risk cracking the bitumen and failing solubility specs.
How much does it cost to produce one tonne of blown asphalt?
Total production cost runs $420–$570 per tonne, of which feedstock is 70–80%. Finished product sells FOB at $480–$650 per tonne, leaving a margin of $40–$90/tonne at typical export scale.
What is the difference between blown asphalt and oxidized bitumen?
None — they are the same product. "Blown" describes the process (air blowing); "oxidized" describes the chemistry. The trade uses both terms interchangeably, along with "industrial asphalt."
Can blown asphalt be used for road paving?
No. With penetration of 10–30 dmm and ductility under 10 cm, blown asphalt is too brittle for roads and cracks under traffic loading. Use penetration grades 40/50 to 80/100 for paving instead.
Calculate Your Blown Asphalt Cost Instantly
Feedstock prices, freight rates, and catalyst costs shift weekly — a spreadsheet built last quarter is already wrong. Use the 6Tar cost calculator to plug in your current bitumen price, energy cost, batch size, and target grade, and get a live cost-per-tonne and margin estimate for every blown asphalt grade in seconds. Whether you are buying Type III for membrane production or quoting Type IV pipe-coating lots, run the numbers first — then negotiate with data on your side.