Emulsion CSS-1 vs CSS-1h Comparison
Last updated: 2026-10-06
Emulsion CSS-1 vs CSS-1h: Key Differences at a Glance
CSS-1 and CSS-1h are both anionic cationic slow-setting asphalt emulsions, but CSS-1h is a higher-residue grade — typically 65–70% residue versus 57–63% for CSS-1. That difference translates into roughly 10–15% less water to transport per ton of residual asphalt, which cuts freight cost and application time on chip seal and slurry projects. In practical terms, CSS-1 is the general-purpose workhorse for diluted tack coats and micro-surfacing, while CSS-1h is preferred for chip seals, slurry seals, and cold in-place recycling (CIR) where a faster-set, higher-binder film is needed.
Below is a direct side-by-side breakdown of specifications, pricing, applications, and supplier selection criteria for buyers sourcing either grade at export scale.
Specification Comparison: CSS-1 vs CSS-1h
The two grades share the same anionic cationic chemistry (CSS = Cationic Slow-Setting) but diverge on residue and viscosity thresholds. The table below reflects ASTM D2397 / AASHTO M208 typical values for each grade.
| Parameter | CSS-1 | CSS-1h | Test Method |
|---|---|---|---|
| Residue by evaporation, % | 57 min | 65 min (typ. 67) | ASTM D6934 |
| Saybolt Furol viscosity @ 25°C, s | 20–100 | 40–150 | ASTM D7496 |
| Penetration @ 25°C, 100 g, 5 s | 100–200 | 40–90 | ASTM D5 |
| Particle charge | Positive | Positive | ASTM D7402 |
| Sieve test, % retained | 0.1 max | 0.1 max | ASTM D6933 |
| Storage stability, 24 h, % | 1 max | 1 max | ASTM D6930 |
| Cement mixing, % | 2.0 max | 2.0 max | ASTM D6935 |
| pH | 2.0–6.5 | 2.0–6.5 | ASTM E70 |
| Shelf life | 6 months | 6 months | — |
Key takeaway: the penetration difference (100–200 vs 40–90 dmm) is the single most important spec. CSS-1h leaves a harder residual film, which matters on high-volume roads where rutting and bleeding are a concern. CSS-1's softer residue performs better in cold climates where flexibility under thermal cracking is critical.
- Residue gap: ~7 percentage points higher for CSS-1h → fewer tanker loads
- Viscosity gap: CSS-1h runs thicker, requiring slightly higher spray temperatures (typically 65–85°C vs 50–70°C)
- Penetration gap: CSS-1h produces a stiffer binder film — better for chip seal retention
- Storage stability: equivalent across both grades at ≤1% separation over 24 hours
Price, Tonnage & Freight Economics
Emulsion pricing is quoted on a per metric ton (MT) of emulsion basis, but the real cost is per ton of residual asphalt (residue). This is where CSS-1h usually wins on delivered cost.
| Cost Component | CSS-1 | CSS-1h | Notes |
|---|---|---|---|
| FOB price, USD/MT emulsion | $420–$520 | $460–$570 | 2024–2025 export range |
| Residue content, % | 60 (typ.) | 67 (typ.) | — |
| Residual asphalt cost, USD/MT residue | $700–$867 | $687–$851 | Lower is better |
| Water hauled per MT residue, kg | 667 | 493 | 174 kg saved with CSS-1h |
| 20 MT container load, MT residue | 12.0 | 13.4 | +11.7% usable binder |
| Ocean freight, USD/MT residue | $48–$62 | $43–$55 | Fewer containers per project |
| Typical MOQ, MT (flexitank) | 20–24 | 20–24 | Flexitank or IBC |
| Lead time, days | 21–35 | 21–35 | Ex-Middle East/Asia |
Worked example (1,000 MT project):
- CSS-1: 600 MT residue, 11 flexitank containers of 24 MT each → ~$53K freight
- CSS-1h: 670 MT residue, 11 flexitank containers → ~$53K freight, but +70 MT of usable binder
- Net effect: ~10.5% more binder delivered for the same freight spend with CSS-1h
For buyers running chip seal or CIR programs above 500 MT/season, the freight-adjusted savings from CSS-1h typically land between $18–$32 per MT of residue — enough to offset a $40–$50/MT premium on the emulsion itself in volume contracts.
Application Guide: Where Each Grade Performs Best
Choosing between CSS-1 and CSS-1h is fundamentally a project-type decision, not a price decision. The higher residue and harder penetration of CSS-1h suit applications demanding rapid binder build and aggregate retention.
- Diluted tack coats at 1:1 to 3:1 water ratio (typical application rate 0.15–0.30 L/m²)
- Micro-surfacing (with polymer modification) on low-to-medium traffic roads, <5,000 AADT
- Fog seals where flexibility is critical
- Cold regions with design temperatures below −20°C (softer residue resists cracking)
- Prime coats on granular bases before asphalt layering
- Chip seals (single/double) on highways >10,000 AADT, at 1.4–2.0 L/m² residual application
- Slurry seals needing high binder content without dilution
- Cold in-place recycling (CIR) — typically 3–5% emulsion by weight of RAP
- Gravel road dust control / surface treatment where fast cure reduces traffic downtime
- Hot-climate projects where stiffer residue resists flushing
| Application | Recommended Grade | Residual Application Rate | Cure Time (typ.) |
|---|---|---|---|
| Diluted tack coat | CSS-1 | 0.15–0.30 L/m² | 30–60 min |
| Chip seal (single) | CSS-1h | 1.4–1.8 L/m² | 2–4 h |
| Chip seal (double) | CSS-1h | 1.8–2.2 L/m² | 4–8 h |
| Micro-surfacing | CSS-1 (+polymer) | 1.0–1.5 kg/m² | 60–90 min |
| Slurry seal Type II/III | CSS-1h | 0.8–1.4 kg/m² | 1–2 h |
| CIR (full depth) | CSS-1h | 3–5% by RAP weight | 7–14 days |
Mixing rule of thumb: never substitute CSS-1h for CSS-1 in a diluted tack coat without re-checking viscosity — the higher residue will clog spray nozzles if not heated correctly, and it will not dilute to the same target application rate.
Storage, Handling & Shelf Life
Both grades are cationic emulsions, meaning they are positively charged and will break instantly if contaminated with anionic materials (soaps, clay dust, hard water with high negative colloid content). This is a common cause of field failures in export markets.
- Storage tanks: mild steel or stainless; coat with corrosion-resistant epoxy if storing >30 days
- Temperature: store at 10–30°C; do not allow cycling above 50°C or below 5°C (freezing is irreversible for both grades)
- Agitation: recirculate gently once per 24 hours for 5–10 minutes to prevent skinning; avoid high-shear pumping
- Shelf life: 6 months from manufacture when stored per above; 3 months in hot climates (>35°C ambient)
- Contamination: never share hoses, pumps, or tanks with anionic emulsions; flush lines between grades
- Dilution: CSS-1 dilutes cleanly up to 3:1 with potable water; CSS-1h generally used undiluted except for specific chip seal designs
| Handling Factor | CSS-1 | CSS-1h |
|---|---|---|
| Recommended spray temp. | 50–70°C | 65–85°C |
| Max storage temp. | 50°C | 50°C |
| Freeze protection | Required | Required |
| Pump type | Progressive cavity or gear | Progressive cavity |
| Dilution capability | Up to 3:1 | Typically neat |
Sourcing & Supplier Selection
For bulk export buyers, both grades are supplied in ISO flexitanks (20–24 MT), IBC totes (1 MT), or drums (200 kg). Most Middle East and Southeast Asian refineries produce both grades under ASTM D2397 or EN 13808 (as C60BP4 / C67BP2 respectively).
- MOQ: 20 MT (single flexitank) for trial orders; 200 MT+ for direct refinery contracts
- Lead time: 21–35 days FOB; add 15–30 days for destination port clearance
- Documentation: COA per batch, MSDS (GHS-compliant), test certificate referencing ASTM D2397
- Payment terms: L/C at sight, or 30% T/T deposit + 70% against BL copy for repeat buyers
- Price drivers: base bitumen (60/70 or 85/100 pen) cost accounts for ~70–75% of emulsion price; emulsifier chemistry adds 8–12%
- Due diligence: verify the emulsion plant is within 200 km of a bitumen source — anything further adds $15–25/MT
When comparing quotes, always normalize to $/MT of residue, not $/MT of emulsion. A supplier quoting CSS-1 at $440/MT (60% residue = $733/MT residue) is more expensive than one quoting CSS-1h at $490/MT (67% residue = $731/MT residue).
FAQ: Emulsion CSS-1 and CSS-1h
Q1: What is the main difference between CSS-1 and CSS-1h?
CSS-1 contains 57–63% residual asphalt, while CSS-1h contains 65–70%. CSS-1h also leaves a harder residual film (penetration 40–90 dmm vs 100–200 dmm), making it better for chip seals and high-traffic surface treatments, while CSS-1 is preferred for tack coats and micro-surfacing.
Q2: Can CSS-1h be used instead of CSS-1?
Physically yes, but not always economically or technically. CSS-1h is thicker and harder-setting, so it can clog spray equipment set for diluted CSS-1 and produces a stiffer film that may crack in cold climates. Always re-verify application rate and spray temperature (65–85°C for CSS-1h) before substituting.
Q3: Which grade is cheaper per ton of actual asphalt?
Usually CSS-1h. Although its emulsion price is $40–$50/MT higher, its higher residue content means you pay for ~7% less water per ton of binder. On a 1,000 MT project that's roughly 70 extra MT of usable asphalt for the same freight cost, which typically delivers $18–$32/MT residue net savings.
Q4: What is the shelf life of CSS-1 and CSS-1h?
Both have a 6-month shelf life when stored at 10–30°C with gentle daily recirculation. In hot climates above 35°C, expect 3 months. Freezing is irreversible for both grades, and any contamination with anionic materials will cause immediate breaking.
Q5: What is the minimum order quantity for export?
Standard MOQ is one flexitank (20–24 MT) for trial shipments. Volume contracts typically start at 200 MT direct from refinery, with 21–35 day lead times FOB Middle East or Southeast Asia, and L/C at sight or 30/70 T/T payment terms.
Calculate Your Delivered Emulsion Cost with 6Tar
Freight, residue content, and FX swings can swing your true emulsion cost by 15–25% — which is why buyers using flat per-MT quotes consistently overpay. Use the 6Tar cost calculator to model landed cost for CSS-1 vs CSS-1h side by side: enter your project tonnage, destination port, residue target, and current FOB quote, and get $/MT of residue plus total project cost in seconds. Start your next tender with real freight-adjusted numbers instead of guesswork.