Rc-70 Cutback Specifications
Last updated: 2026-10-17
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Rc-70 Cutback Specifications
RC-70 cutback asphalt is a rapid-curing (RC) liquid asphalt cement with a kinematic viscosity of 70 seconds (Saybolt Furol at 140°F / 60°C), produced by blending 60–70% penetration-grade bitumen with roughly 30–40% naphtha or light petroleum distillate as the solvent. It conforms primarily to ASTM D2026 / D2027 and AASHTO M81 / M82 tolerances, with flash point typically above 80°F (27°C), distillation residue of at least 55% by volume, and a typical bulk price range of USD 320–480 per metric ton depending on solvent ratio, origin, and freight.
What Is RC-70 Cutback Asphalt?
RC-70 (also written RC-70, RC 70, or RC70) is a rapid-curing cutback bitumen in which the cutter stock is a volatile petroleum solvent — naphtha, gasoline, or a light distillate — that evaporates quickly after application, leaving the residual asphalt binder to harden. The number "70" denotes viscosity, not penetration grade: the product is graded so that it falls within a Saybolt Furol viscosity window at 140°F.
It is used mainly for prime coats, tack coats, cold-laid surface treatments, and penetration macadam, where fast curing and early traffic opening matter more than long-term flexibility. Because the solvent flashes off rapidly, RC grades cure faster than medium-curing (MC) or slow-curing (SC) cutbacks, which is why they dominate applications requiring a return to service within 2–8 hours.
Key differentiators vs. other cutbacks:
- Curing speed: RC > MC > SC
- Solvent type: RC uses naphtha/gasoline (high volatility)
- Primary standard: ASTM D2026 (specification), ASTM D402 / D20 for testing
- Typical application rate: 0.15–0.55 L/m² for prime and tack coats
RC-70 Cutback Specifications: Full Data Table
The following table reflects the standard ASTM D2026 / AASHTO M81 requirements for RC-70, cross-referenced with common supplier datasheets. Values are typical ranges found in export-grade material.
| Property | Standard (ASTM D2026) | Typical Supplier Range |
|---|---|---|
| Kinematic viscosity, Saybolt Furol @ 140°F (60°C) | 60–120 s | 70 s (nominal) |
| Flash point (Tag open cup) | Min 80°F (27°C) | 85–110°F |
| Distillation: total distillate to 680°F (360°C) | 45–80% by volume | 55–70% |
| Residue from distillation, % by volume | Min 55% | 57–62% |
| Residue penetration @ 77°F, 100 g, 5 s | 80–120 dmm | 90–110 dmm |
| Residue viscosity, Saybolt Furol @ 140°F | Min 100 s | 105–140 s |
| Solubility in trichloroethylene | Min 99.0% | 99.2–99.8% |
| Water content | Max 0.2% | 0.05–0.15% |
| Specific gravity @ 77°F | Report | 0.90–0.96 |
| Solvent content (naphtha) | ~30–40% | 32–38% |
Bold figures indicate the values most often quoted in commercial contracts and tender documents. Note that viscosity is the defining parameter — a batch reading below 60 s is RC-250 territory, and above 120 s fails the RC-70 window.
RC-70 vs RC-250 vs RC-800: Viscosity Comparison
Curing and viscosity are inversely related across the RC family. Lower viscosity means faster penetration into a base course and lower application rates.
| Grade | Saybolt Furol Viscosity @ 140°F | Flash Point (min) | Typical Use |
|---|---|---|---|
| RC-70 | 60–120 s | 80°F | Prime coat, tack coat, light surface treatment |
| RC-250 | 200–400 s | 80°F | Heavier prime, penetration macadam |
| RC-800 | 800–1,600 s | 80°F | Cold mix, dense-graded cold-laid |
| RC-3000 | 3,000–6,000 s | 80°F | Specialty cold patching |
Practical implication: RC-70 is the most fluid of the commonly traded RC grades after RC-30, giving deeper penetration into granular bases and enabling lower application rates. If you need a longer working time before cure, step up to RC-250; if you need a thicker residual film, RC-800 or RC-3000.
RC-70 vs MC-70 vs SC-70: Curing Speed Comparison
The "70" suffix is shared across RC, MC, and SC families, but solvent chemistry changes everything.
| Parameter | RC-70 | MC-70 | SC-70 |
|---|---|---|---|
| Solvent type | Naphtha / gasoline | Kerosene / medium distillate | Heavy oil / low-volatility |
| Curing speed | Fast (2–8 h) | Moderate (6–24 h) | Slow (24–72 h+) |
| Flash point (min) | 80°F | 100°F | 150°F |
| Safety profile | Highest flammability | Moderate | Lowest |
| Best use | Prime/tack, cold surface treatment | Stockpile mixes, dust control | Dust laying, slow-cure base work |
| ASTM spec | D2026 | D2027 | D2028 |
Comparison note: For prime coat on a crushed-stone base where rain is forecast within 24 hours, RC-70 is the safer choice because it cures before the weather event. For applications where the solvent must persist for weeks (dust palliative), SC grades are preferred.
Distillation Curve and Solvent Fraction Data
Distillation behavior controls cure rate and is the second-most scrutinized spec after viscosity. RC-70 distillation limits are set so the solvent boils off progressively between ambient temperature and 680°F.
| Distillation Cut | ASTM Limit (% by volume) | Typical RC-70 Result |
|---|---|---|
| To 437°F (225°C) | Max 35% | 25–32% |
| To 500°F (260°C) | 45–80% | 55–68% |
| To 680°F (360°C) | 45–80% cumulative | 60–72% |
| Residue | Min 55% | 57–62% |
Interpretation for buyers:
- A higher "to 437°F" fraction means more highly volatile solvent — faster cure but greater flashing and fire risk.
- A residue at the low end (55–57%) means more solvent per ton — cheaper per ton but poorer binder yield after cure.
- Contract terms should specify residue by volume, not by weight, and a maximum solvent content, otherwise suppliers can shortchange binder content by a few percentage points worth USD 8–15 per ton.
RC-70 Application Rates and Performance Data
Application rate depends on surface texture, base porosity, and climate. The table below uses standard prime/tack coat practice.
| Application | Typical Rate | Residual Binder After Cure | Cure Time |
|---|---|---|---|
| Prime coat, granular base | 0.30–0.55 L/m² | 0.18–0.33 L/m² | 4–8 h |
| Tack coat, primed surface | 0.15–0.30 L/m² | 0.09–0.18 L/m² | 2–4 h |
| Surface treatment (single seal) | 0.90–1.40 L/m² | 0.55–0.85 L/m² | 2–6 h |
| Penetration macadam binder | 4.0–6.0 L/m² | 2.5–3.7 L/m² | 6–12 h |
Quick conversion figures for estimating tonnage:
- 1 L/m² ≈ 0.95 kg/m² for RC-70 at specific gravity 0.94
- 1 km of 3.5 m lane at 0.4 L/m² ≈ 1.33 metric tons of RC-70
- 100,000 m² at 0.35 L/m² ≈ 33.3 metric tons
Note on temperature: Apply between 50°F and 110°F (10–43°C) ambient. Below 50°F the solvent does not flash off reliably; above 110°F flash-off can be violent and the residual film may be uneven.
Safety, Handling, and Storage Specifications
RC-70 is a flammable liquid Class IB/IC depending on flash point. The naphtha fraction is the risk driver.
- Flash point: minimum 80°F (27°C) — many suppliers deliver 85–110°F
- Auto-ignition: not applicable to cutbacks; ignition is source-of-vapor driven
- Storage temperature: ambient to 120°F preferred; do not heat above 150°F
- Heating: steam coils only; open flame prohibited
- Vapor control: closed tanks with pressure-vacuum vents; bonding and grounding mandatory
- PPE: nitrile gloves, chemical splash goggles, organic-vapor respirator for confined work
- Shelf life: 6–12 months in sealed drums; solvent loss reduces flash point over time
- Drum packaging: 180 kg net drums, 20 drums per pallet; bulk in ISO tanks (~20–24 MT net)
Shipping classification:
- UN 1993, Flammable Liquid, n.o.s., Class 3, PG III (typical)
- Marine pollutant: not generally listed for standard formulations
Pricing and Market Data for RC-70
RC-70 pricing is driven by three inputs: penetration-grade base bitumen, naphtha solvent, and logistics. Because the solvent fraction is roughly 30–40% of the blend, naphtha crack spreads directly move RC-70 prices.
| Cost Component | Share of Delivered Price | Driver |
|---|---|---|
| Base bitumen (pen grade) | 55–65% | Crude oil, refinery runs |
| Naphtha / solvent | 20–30% | Gasoline crack spreads, seasonality |
| Packaging + freight | 10–20% | Drums, ISO tanks, distance |
Indicative bulk price ranges (FOB, export):
- Penetration-grade base bitumen: USD 380–520/MT
- RC-70 finished cutback (bulk): USD 320–480/MT
- Drums, ex-works: add USD 30–60/MT for packaging
- ISO tank, to port: add USD 40–90/MT for maritime freight & handling
Rule of thumb: RC-70 typically trades at a 5–15% discount to base pen grade on a per-ton basis because roughly one-third of the mass is low-cost solvent, though the discount narrows when naphtha cracks are high.
FAQ: RC-70 Cutback Specifications
What is the viscosity of RC-70 cutback asphalt?
RC-70 has a Saybolt Furol viscosity of 60–120 seconds at 140°F (60°C), with a nominal target of 70 seconds. This viscosity window is the defining specification, and any batch outside 60–120 s does not qualify as RC-70 under ASTM D2026.
What does the "RC" in RC-70 stand for, and why does it matter?
"RC" stands for rapid curing, meaning the solvent is a volatile naphtha or gasoline fraction that evaporates within 2–8 hours of application. It matters because rapid curing allows faster return to traffic, earlier rain resistance, and quicker layering of subsequent courses compared with MC or SC cutbacks.
How much residual asphalt remains after RC-70 cures?
RC-70 must leave a distillation residue of at least 55% by volume, with typical commercial product yielding 57–62%. This means roughly 380–410 kg of residual binder per metric ton of cutback, and buyers should specify residue by volume in the contract.
What is the flash point requirement for RC-70?
The minimum flash point for RC-70 is 80°F (27°C) per ASTM D2026, though suppliers commonly deliver 85–110°F. Because this is a low flash point, RC-70 is classified as a flammable liquid Class 3 for transport and requires grounding, bonding, and vapor control during handling.
How many liters of RC-70 are in a metric ton?
At a typical specific gravity of 0.94, one metric ton of RC-70 equals approximately 1,064 liters. This conversion is essential for estimating spray rates — for example, 33.3 metric tons covers 100,000 m² at an application rate of 0.35 L/m².
Closing CTA: Cost Out Your RC-70 Project with 6Tar
Getting the landed cost right on RC-70 requires more than a quoted FOB number — solvent fraction, drum versus bulk packaging, ISO tank freight, port charges, and inland trucking all shift the final figure by USD 40–120 per metric ton. Before you commit to a tender or a shipment, run the numbers through the 6