Marshall Stability Test: Equipment, Procedure & Standards
Published November 2025 Β· 6 min read Β· Elipslab Technical Team
What Is the Marshall Stability Test?
The Marshall stability test is a standard laboratory method for evaluating the mechanical properties of compacted asphalt concrete mixes. It measures two parameters: stability (the maximum load a specimen can withstand before failure) and flow (the deformation at the point of failure). Together, these values help engineers assess whether an asphalt mix design is suitable for road construction.
The test is governed primarily by ASTM D6927 (Standard Test Method for Marshall Stability and Flow of Asphalt Mixtures) and EN 12697-34 (Bituminous Mixtures β Test Methods for Hot Mix Asphalt β Marshall Stability and Flow). Both standards require similar equipment but differ in specimen size and test conditions.
Required Equipment
A complete Marshall stability test setup requires the following equipment:
- Marshall Stability Testing Machine β applies load at a constant rate of 50.8 mm/min (2 in/min). Capacity: typically 25 kN or 50 kN.
- Marshall Compactor β a mechanical or automatic compactor for preparing cylindrical specimens (100 mm or 150 mm diameter).
- Water Bath β maintains specimen temperature at 60Β°C Β± 1Β°C during conditioning (ASTM D6927).
- Breaking Heads β curved steel heads matching specimen diameter.
- Flow Meter / Dial Gauge β measures deformation during loading (flow value in 0.25 mm units).
- Thermometer β for verifying water bath temperature.
- Extraction Molds β cylindrical molds (100 mm Γ 63.5 mm for ASTM; 101.6 mm Γ 63.5 mm for EN).
Test Procedure (ASTM D6927)
- Specimen preparation: Prepare cylindrical asphalt specimens using the Marshall compactor. ASTM D6927 specifies 75 blows per face for heavy traffic mixes. Allow specimens to cool to room temperature before testing.
- Conditioning: Immerse specimens in a water bath at 60Β°C Β± 1Β°C for 30β40 minutes. This simulates summer road surface temperatures.
- Transfer and setup: Remove specimen from bath, dry the surface, and place it in the breaking head assembly.
- Loading: Apply load at 50.8 mm/min. Record the maximum load (stability) and the deformation at failure (flow).
- Correction: Apply a stability correction factor if the specimen height deviates from the standard 63.5 mm.
ASTM D6927 vs EN 12697-34: Key Differences
| Parameter | ASTM D6927 | EN 12697-34 |
|---|---|---|
| Specimen diameter | 101.6 mm (4 in) | 101.6 mm or 152.4 mm |
| Water bath temp | 60Β°C Β± 1Β°C | 60Β°C Β± 1Β°C |
| Loading rate | 50.8 mm/min | 50 mm/min |
| Conditioning time | 30β40 min | 30β40 min |
| Stability unit | lbf or kN | kN |
| Flow unit | 0.01 in (0.25 mm) | 0.1 mm |
Interpreting Results
Typical stability values for road asphalt mixes range from 5 kN to 18 kN, depending on traffic load and mix type. Flow values between 2 mm and 4 mm are generally acceptable for dense graded mixes. Mixes with low stability or excessive flow should be redesigned before use.
Results are also compared across multiple binder content levels to identify the optimum asphalt content (OAC) β the binder percentage that simultaneously achieves target stability, flow, air voids, and VMA values.
Choosing a Marshall Stability Testing Machine
When selecting a Marshall stability tester, consider:
- Capacity: 25 kN is sufficient for standard mixes; 50 kN for heavy-duty applications.
- Standards compliance: Ensure the machine meets both ASTM D6927 and EN 12697-34 if dual-standard operation is required.
- Automatic vs manual: Automatic testers with digital load cells and built-in data logging reduce operator variability.
- Breaking head set: Verify the heads match your specimen diameter (100 mm or 150 mm).
Need a Marshall Stability Tester?
Elipslab manufactures Marshall stability testing machines compliant with ASTM D6927 and EN 12697-34, including automatic models with digital load cells, water baths, and compactors. Based in Ankara, Turkey β shipping worldwide.