Bitumen Emulsion Settlement Test
Last updated: 2026-10-01
Bitumen Emulsion Settlement Test: Direct Answer
The bitumen emulsion settlement test measures the tendency of bitumen droplets to separate from the water phase during storage, and a passing result requires ≤5% residue difference between top and bottom samples after 5 days of static storage at 20°C (ASTM D6930 / EN 12847). Emulsions that exceed 5% settlement typically fail within 7–14 days in bulk tanks, forcing suppliers to apply 2–5% additional mixing energy or accept $15–40 per tonne in rework losses. For exporters shipping 20–24 tonne ISO tanks, a failed settlement test can delay a $400–600/tonne cargo and trigger demurrage charges of $8,000–15,000 per day.
What Is the Bitumen Emulsion Settlement Test?
Bitumen emulsion settlement is the gravitational separation of bitumen globules from the continuous water phase. Because bitumen has a density of roughly 1.01–1.05 g/cm³ and water sits near 1.00 g/cm³, emulsions are thermodynamically unstable — they will separate given enough time.
The settlement test quantifies that instability in two ways:
- Settlement (bottom enrichment): bitumen concentrates at the bottom of the container
- Creaming (top enrichment): lighter or flocculated droplets rise
| Standard | Region | Sample Size | Storage Period | Temperature | Pass/Fail Criterion |
|---|---|---|---|---|---|
| ASTM D6930 | USA | 500 mL | 5 days | 20°C | ≤5% residue difference |
| EN 12847 | EU | 500 mL | 5 days | 20°C | ≤5% (some specs ≤10%) |
| IS 8887 | India | 500 mL | 5 days | 20°C | ≤5% for cationic |
| AASHTO T59 | USA (alt) | 500 mL | 5 days | 20°C | ≤5% residue difference |
| JTG E20 T0655 | China | 500 mL | 5 days | 20°C | ≤5% (CSS-1h ≤3%) |
1. Fill a 500 mL graduated cylinder to the 250 mL mark with emulsion at 20°C
2. Cover and store undisturbed for 5 days (120 hours)
3. Remove the top 50 mL and bottom 50 mL with a pipette
4. Determine residue content of each portion (evaporation or distillation)
5. Calculate the difference in residue percentage
A 3.2% settlement is considered excellent. A 6.8% settlement is a fail and signals a formulation or storage problem.
Key Factors Driving Settlement Rates
Settlement is not random. It is governed by measurable physical and chemical variables.
| Factor | Typical Range | Effect on Settlement | Commercial Consequence |
|---|---|---|---|
| Storage time | 0–30 days | Linear to exponential increase | >7 days risks tank stratification |
| Storage temperature | 5–40°C | Higher temp = faster separation | >30°C can double settlement rate |
| Bitumen droplet size | 1–20 µm | Smaller = slower settlement | Sub-5 µm emulsions hold 2–3× longer |
| Emulsifier dosage | 0.3–1.5% | Higher = better stability | +0.2% adds $4–8/tonne cost |
| pH (anionic/cationic) | 2–12 | Off-spec pH = rapid flocculation | Batch rejection risk |
| Solids content | 55–70% | Higher solids = faster settling | 65%+ needs stabilizer |
| Viscosity | 20–200 cP | Higher = slower settling | Thick emulsions store better |
| Mechanical agitation | 0–500 rpm | Mild mixing disperses; excess shears | Over-pumping breaks emulsion |
| Mean Droplet Size | 5-Day Settlement | Storage Life (est.) |
|---|---|---|
| 1–3 µm | 0.5–1.5% | 90+ days |
| 3–5 µm | 1.5–3.0% | 45–60 days |
| 5–10 µm | 3.0–5.0% | 20–30 days |
| 10–20 µm | 5.0–9.0% | 7–14 days |
| >20 µm | >9.0% | <5 days |
The practical takeaway: if you need 30-day storage, specify a mean droplet size below 5 µm and verify with a laser diffraction particle size analyzer.
Settlement Test Results: What the Numbers Mean
Interpreting settlement data correctly prevents both over-rejection and field failure.
| Settlement Result | Classification | Action Required | Risk Level |
|---|---|---|---|
| 0–1% | Excellent | None | Very low |
| 1–3% | Good | Standard storage | Low |
| 3–5% | Acceptable (borderline) | Limit storage to 14 days | Moderate |
| 5–7% | Marginal fail | Re-mix before use; investigate formula | High |
| 7–12% | Fail | Reject batch or re-emulsify | Severe |
| >12% | Critical fail | Batch loss; root cause analysis | Critical |
| Scenario | Volume | Loss per Tonne | Total Loss |
|---|---|---|---|
| Marginal re-mix | 20 t tanker | $6–12 | $120–240 |
| Batch rejection | 20 t | $400–600 | $8,000–12,000 |
| ISO tank rework | 24 t | $25–40 | $600–960 |
| Delayed shipment (3 days demurrage) | 24 t | — | $24,000–45,000 |
| Full cargo loss (20,000 t vessel) | 20,000 t | $400+ | $8,000,000+ |
At vessel scale, a 0.5% settlement improvement in a 20,000-tonne parcel is worth roughly $40,000–80,000 in avoided rework and demurrage.
How to Prevent Bitumen Emulsion Settlement
Prevention is cheaper than correction. The highest-ROI controls sit in formulation, storage, and handling.
- Formulation
- Use emulsifier dosages at the upper end of spec (1.0–1.5%) for long-storage grades
- Target mean droplet size 2–5 µm via high-shear colloid mill settings
- Add 0.1–0.3% stabilizers (e.g., cellulose ethers, xanthan gum) for tropical shipment
- Maintain pH within ±0.5 of the design value
- Storage
- Keep tanks at 15–25°C; avoid >30°C
- Apply gentle recirculation (20–50 rpm equivalent) every 48–72 hours
- Use tall, narrow tanks rather than wide, flat ones
- Never store beyond the validated shelf life (typically 30–90 days)
- Handling
- Avoid over-pumping (>500 rpm shear)
- Do not freeze the emulsion — freezing is irreversible
- Seal tanks to prevent evaporation and skin formation
| Recirculation Frequency | 30-Day Settlement (est.) | Verdict |
|---|---|---|
| None | 6–10% | Fail |
| Every 14 days | 3–5% | Borderline |
| Every 7 days | 2–4% | Good |
| Every 48–72 hours | 1–3% | Excellent |
| Continuous low-shear | 0.5–2% | Optimal (energy cost) |
| Modification | Added Cost/Tonne | Settlement Reduction | Payback Threshold |
|---|---|---|---|
| Emulsifier +0.2% | $4–8 | 20–30% | >10 t batches |
| Stabilizer +0.2% | $3–6 | 30–45% | >5 t batches |
| Droplet size optimization | $1–3 | 40–60% | Always |
| Temperature control | $2–5 | 15–25% | Warm climates |
For exporters moving 500+ tonnes per month, formulation upgrades typically pay back within one avoided rejection.
Settlement Test vs. Other Stability Tests
Settlement is only one stability indicator. A complete quality package combines several.
| Test | What It Measures | Method | Typical Spec |
|---|---|---|---|
| Settlement | Storage separation | ASTM D6930 | ≤5%, 5 days |
| Storage stability | Long-term separation | EN 12847 | ≤5%, 5 days |
| Particle charge | Emulsifier type | ASTM D7402 | Cationic/anionic |
| Viscosity (Saybolt) | Handling consistency | ASTM D7496 | 20–200 s |
| Residue content | Bitumen yield | ASTM D6997 | 55–70% |
| Sieve test | Oversized particles | ASTM D6933 | ≤0.1% |
| Cement mixing | Coating ability | ASTM D6935 | Pass/fail |
A batch that passes viscosity but fails settlement points to a formulation problem, not a production problem. A batch that fails both usually indicates a mill malfunction or off-spec raw bitumen.
| Settlement | Sieve | Viscosity | Diagnosis | Action |
|---|---|---|---|---|
| Pass | Pass | Pass | Healthy | Ship |
| Fail | Pass | Pass | Formulation drift | Re-emulsify |
| Pass | Fail | Pass | Mill malfunction | Filter, retest |
| Pass | Pass | Fail | Solids/water imbalance | Adjust, remix |
| Fail | Fail | Fail | Raw material fault | Reject batch |
Cost Impact: Settlement Failure Across the Supply Chain
Settlement failures cascade. Understanding the full cost chain helps procurement teams justify premium specs.
| Stage | Failure Cost | Trigger | Mitigation |
|---|---|---|---|
| Production | $25–60/t | Out-of-spec batch | In-line particle sizing |
| ISO tank export | $600–960/tank | Re-test failure | Pre-shipment 5-day test |
| Bulk vessel | $8M+ | Cargo rejection | Certificate of analysis + third-party |
| Road tanker | $120–240 | Re-mix needed | Short-haul supply chains |
| Application | $0.50–2.00/m² | Streaking, poor bond | On-site mixing before spray |
| Warranty claim | $5,000–50,000/project | Premature surface failure | Batch traceability |
| Product | Typical Price (USD/tonne) | Settlement Sensitivity |
|---|---|---|
| Cationic slow-setting (CSS-1h) | $400–600 | High (long storage) |
| Anionic rapid-setting (RS-1) | $380–520 | Medium |
| Polymer-modified emulsion | $650–900 | Low (stabilized) |
| Micro-surfacing emulsion | $700–950 | Medium-high |
Because polymer-modified and micro-surfacing emulsions carry the highest price tags, a settlement failure at $700–950/tonne is proportionally more painful than at commodity grade.
FAQ: Bitumen Emulsion Settlement
Q1: What is an acceptable settlement result in a bitumen emulsion test?
A settlement of ≤5% residue difference between the top and bottom 50 mL samples after 5 days at 20°C is the global industry benchmark per ASTM D6930 and EN 12847. Results between 3% and 5% are technically passing but signal borderline storage stability, so many buyers specify ≤3% for long-haul or long-storage applications. Anything above 7% should trigger batch rejection or re-emulsification.
Q2: How long can bitumen emulsion be stored before settlement becomes a problem?
Most standard emulsions remain stable for 30–90 days when stored at 15–25°C with periodic recirculation. Without agitation, detectable settlement typically appears after 7–14 days, and a 5-day lab test at 20°C is used to predict this behavior. For shipments exceeding 30 days, opt for polymer-modified or stabilizer-enhanced grades.
Q3: Does temperature affect bitumen emulsion settlement?
Yes, strongly. Raising storage temperature from 20°C to 30°C can increase the settlement rate by 40–80% because lower viscosity accelerates droplet movement. Conversely, storing near 5°C slows settlement but risks freezing, which permanently breaks the emulsion. The safe window is 15–25°C with minimal thermal cycling.
Q4: How do you fix a bitumen emulsion that has settled?
Mild settlement up to 5–7% can often be reversed with gentle recirculation (20–50 rpm equivalent for 15–30 minutes) before use. Settlement above 7% usually indicates irreversible flocculation or coalescence, and the batch must be