Bitumen Emulsion Settlement Test
Last updated: 2026-09-30
Bitumen Emulsion Settlement Test: The Complete Guide for B2B Buyers and Suppliers
Bitumen emulsion settlement test measures the tendency of asphalt particles to separate from the water phase during storage — acceptable settlement is typically ≤5% by mass after 5 days (ASTM D6930 / EN 12847), and ≤2% visual settlement after 24 hours for rapid-setting grades. Settlement above 10% within 7 days signals an unstable emulsion that will fail spray application, clog nozzles, and cause non-uniform binder distribution on the road. For exporters shipping 20–25 MT flexitank or drum loads over 30–45 day ocean transit windows, passing the settlement test is the single most important stability indicator you can put in a Certificate of Analysis.
If you buy, sell, or specify bitumen emulsion (CSS-1h, CRS-2, SS-1, CQS-1h, or K1-60), this guide gives you the test methods, pass/fail thresholds, comparison data, and practical troubleshooting numbers you need — in one structured reference.
What Is the Bitumen Emulsion Settlement Test?
The settlement test (also called the storage stability test) determines whether bitumen droplets stay suspended in the aqueous emulsifier solution over time. Because bitumen (~1.01–1.05 g/cm³) is slightly denser than water (~1.00 g/cm³), gravity pulls particles downward. A well-formulated emulsion with the right emulsifier dosage, particle size distribution (1–10 µm, ideally 2–5 µm), and viscosity resists this separation.
Two standard methods dominate global trade:
| Method | Standard | Sample | Duration | Pass Threshold |
|---|---|---|---|---|
| Settlement by mass (residue difference) | ASTM D6930 | 500 g in 500 mL cylinder | 5 days @ 20–25°C | ≤5% difference top vs. bottom |
| Settlement / stability (EN) | EN 12847 | 500 g | 7 days @ 20°C | ≤5% (some specs ≤7%) |
| 24-hour visual stability | AASHTO T59 / field QC | 500 mL | 24 hours | ≤2% free water, no hard cake |
| Accelerated centrifuge | Internal QC | 100 mL | 30 min @ 2,000 rpm | No visible separation |
Key numbers buyers should memorize:
- ≤5% — maximum residue difference for most ASTM/EN-compliant emulsions
- ≤2% — acceptable visual free-water layer at 24 hours
- 5–7 days — standard storage stability observation window
- 20–25°C — required test temperature (each 10°C increase roughly doubles settling rate)
- 6 months — typical maximum recommended storage life for stable emulsion at ambient temperature
Why Settlement Happens: Causes, Severity Levels, and Cost Impact
Settlement is rarely random. It correlates with formulation chemistry, storage conditions, and transit stress. Understanding root causes prevents a $2,000–$15,000 rejected container claim.
| Cause | Frequency | Typical Settlement Result | Fix |
|---|---|---|---|
| Insufficient emulsifier dosage | 35% | 8–20% in 7 days | Increase surfactant 0.1–0.3% by mass |
| Wrong pH (outside 2.0–3.5 for cationic) | 20% | 10–25% | Adjust with HCl |
| Particle size too coarse (>10 µm) | 15% | 6–15% | Re-check colloid mill gap |
| Storage temperature >30°C | 12% | Accelerated 2–3× | Cool storage, avoid direct sun |
| Vibration during ocean transit | 10% | 3–8% | Anti-settling additive, higher viscosity |
| Age >6 months | 8% | Progressive | FIFO stock rotation |
- 0–2%: Excellent. Ship without restriction.
- 2–5%: Acceptable. Meets ASTM D6930. Standard commercial shipment OK.
- 5–10%: Marginal. Requires redispersal check; consider price discount of 3–7%.
- >10%: Reject. Emulsion will not recover on stirring; unusable for spray seal or micro-surfacing.
| Scenario | Volume | Loss per Incident | Notes |
|---|---|---|---|
| Rejected 20 MT flexitank (FOB) | 20 MT | $7,000–$11,000 @ $350–550/MT | Plus return freight $1,500–$3,000 |
| Drum load (150 drums) rework | ~27 MT | $4,000–$9,000 | Redispersal + re-testing |
| Spray job failure, re-application | 1 km seal | $12,000–$30,000 | Crew + material + delay |
Bottom line: a $150–$400 lab test protects against $7,000+ in claims. Settlement screening before loading is non-negotiable for B2B export.
Test Procedure: Step-by-Step with Tolerances
Follow this sequence for a defensible settlement result. Deviating on temperature or sample mass is the number-one cause of disputed CoAs.
Equipment checklist:
- 500 mL graduated cylinder (glass, ±5 mL accuracy)
- Analytical balance (0.01 g precision)
- Oven or water bath at 20 ± 1°C (or 25 ± 1°C per ASTM)
- Rubber stopper / sealing film
- Spatula, stir rod
Procedure (ASTM D6930 basis):
1. Weigh 500 ± 0.5 g of thoroughly mixed emulsion into the cylinder.
2. Seal and record initial mass and residue content (per ASTM D6997 evaporation).
3. Store upright at 20–25°C for 5 days with zero vibration.
4. After the period, sample the top 50 mL and bottom 50 mL separately without mixing the middle.
5. Determine residue of each portion via evaporation (163°C for 3 hours, or EN 13074 method).
6. Calculate: Settlement % = [(bottom residue − top residue) / average residue] × 100.
| Parameter | Target | Acceptable Range | Out-of-Range Effect |
|---|---|---|---|
| Sample mass | 500 g | 495–505 g | Skews % by up to 1% |
| Temperature | 20°C | 19–21°C | 1°C = ~5% rate change |
| Storage duration | 5 days | 120 ± 2 h | Under-storage = false pass |
| Sampling depth | 50 mL top/bottom | ±5 mL | Mixing error ±1.5% |
| Evaporation temp | 163°C | ±3°C | Residue bias 0.3–0.8% |
For fast pre-shipment screening without a full lab:
- Fill 500 mL cylinder, cap, stand 24 hours at 20–25°C.
- Read the free-water layer appearing at the top.
- ≤2% (≤10 mL) = likely pass. >4% (20 mL) = likely fail; send for full test.
Settlement Data: Comparing Grades, Storage Times, and Conditions
These reference figures reflect typical results across common cationic and anionic grades at standard conditions. Use them for benchmarking, not as absolute guarantees — always verify with your supplier's CoA.
| Grade | Type | Typical Settlement | Recommended Max Storage | Use Case |
|---|---|---|---|---|
| CRS-2 | Cationic rapid-set | 1.5–3% | 3 months | Chip seal, tack coat |
| CSS-1h | Cationic slow-set | 0.8–2% | 6 months | Fog seal, micro-surfacing |
| SS-1h | Anionic slow-set | 2–4% | 4 months | Dust palliative, base |
| CQS-1h | Cationic quick-set | 1–2.5% | 4 months | Slurry seal |
| K1-60 | Cationic (EU) | 1–3% | 6 months | General surface dressing |
Observation: Slow-setting grades (CSS-1h, K1-60) generally show lower settlement because of finer particle size and higher emulsifier content — often 0.3–0.6% surfactant by mass vs. 0.15–0.3% for rapid-set.
| Storage Days | Settlement % | Free Water (visual) | Usability |
|---|---|---|---|
| 1 | 0.2–0.5 | ≤0.5% | Full |
| 7 | 1.0–1.8 | 0.5–1.0% | Full |
| 30 | 2.0–3.5 | 1–2% | Full after stirring |
| 90 | 3.5–5.0 | 2–3% | Stir, re-test |
| 180 | 5.0–8.0 | 3–5% | Re-test, may need rework |
| 365 | 8–15%+ | >5% | Likely reject |
| Storage Temp | Relative Settling Rate | Effective 5-Day Settlement (vs. 20°C) |
|---|---|---|
| 10°C | 0.5× | ~50% lower |
| 20°C | 1.0× (reference) | Baseline |
| 30°C | 2.0–2.5× | ~2× higher |
| 40°C | 4.0–5.0× | ~4× higher |
| 50°C (container deck) | 7–10× | Severe risk |
Critical for exporters: A container deck in tropical transit can hit 45–55°C. An emulsion that passes at 2% in the lab can arrive at 8–10%. Use insulated or shaded loading where possible; specify anti-settling additives for routes exceeding 30 days.
| Indicator | Pass Sample | Fail Sample |
|---|---|---|
| Bottom vs. top residue difference | 1.8% | 12.5% |
| Free water at 24 h | 0.5 mL (0.1%) | 45 mL (9%) |
| Particle size (D50) | 2.8 µm | 11.5 µm |
| pH (cationic) | 2.4 | 4.8 |
| Viscosity (Saybolt Furol, 25°C) | 28 s | 62 s |
| Redispersal on stirring | Full recovery | Hard cake, no recovery |
Troubleshooting and Remediation Protocols
When settlement fails, match the corrective action to severity.
If settlement is 2–5% (marginal pass by a hair):
- Stir gently for 5–10 min before use; re-test.
- Ship with instruction: "Stir before application."
- Offer buyer a 1–3% price goodwill adjustment.
If settlement is 5–10% (marginal fail):
- Attempt redispersal: recirculate via pump at 1,000–1,500 rpm for 15 min.
- Re-test top/bottom. If difference drops below 5%, ship with clear documentation.
- If it does not recover, blend with fresh emulsion at ≤20% ratio after lab approval.
If settlement is >10% (hard fail):
- Do not ship for spray application. The emulsion cannot be reliably redispersed.
- Options: (a) return to plant for re-milling, (b) sell as-is to a non-critical use (dust suppression) at 30–50% discount, (c) dispose per local regulations.
- Insert ASTM D6930 ≤5% as an explicit CoA line item.
- Require 24 h free water ≤2%.
- Add "stable after 30-day at 30°C simulated transit" clause for export orders.
- Specify anti-settling additive where transit >30 days or ambient >35°C.
- Mandate third-party pre-shipment sampling for orders >20 MT.
Bullet summary of remediation logic:
- 0–2% → ship, no action.
- 2–5% → stir, ship, minor discount possible.
- 5–10% → redisperse, re-test, blend or discount.
- >10% → reject, rework, or non-critical resale.
FAQ: Bitumen Emulsion Settlement Test
Q1: What is an acceptable settlement value for bitumen emulsion?
Acceptable settlement is ≤5% by mass over 5 days per ASTM D6930, or ≤2% visual free water at 24 hours for field checks. Slow-setting grades like CSS-1h typically test even lower, at 0.8–2%. Anything above 10% in 7 days should be treated as unstable and rejected for spray or micro-surfacing use.
Q2: How long does a bitumen emulsion storage stability test take?
The standard ASTM D6930 test runs 5 days at 20–25°C, while the EN 12847 equivalent runs 7