Step 01
Sample
Loose mix is sampled from the plant or the paver, and cores are cut from the compacted layer at agreed locations.
Asphalt Testing
Whether the asphalt that arrived matches the asphalt that was specified, and whether what was laid was compacted properly. Both questions are answered by measurement, not by appearance.
Asphalt Testing: what it actually tells you
Extraction separates the bitumen from the aggregate so both can be checked. The recovered binder content is compared against the job mix formula, and the aggregate is graded to confirm it still sits inside the specified envelope. A mix that is lean on binder will ravel; one that is rich will rut and bleed.
Marshall testing measures how the compacted mix behaves under load. A specimen compacted to a set number of blows is loaded to failure in the Marshall apparatus, giving stability in kilonewtons and flow in millimetres. Together with the volumetric properties they tell you whether the mix has the strength without becoming brittle.
Volumetrics are where most failures are actually found. Bulk specific gravity of the compacted specimen and theoretical maximum specific gravity of the loose mix give air voids, voids in mineral aggregate and voids filled with bitumen. Air voids outside the specified band is the single most common cause of premature pavement failure, and cores cut from the finished layer show whether the roller achieved what the laboratory did.
At a glance
- Sample typeLoose plant mix and cut cores
- Marshall test temperature60 degrees Celsius
- Typical air voids band3 to 5 percent for wearing course
- Turnaround2 to 4 working days
How we run it
The sequence we follow on site and in the laboratory, and the point of each stage.
Step 02
Extraction and recovery
Binder is removed by centrifuge extraction with solvent, or by ignition, and the binder content is calculated against the total mix mass.
Step 03
Aggregate grading
The recovered aggregate is washed, dried and sieved, and the grading is plotted against the specification envelope.
Step 04
Marshall
Specimens are compacted at the design blow count, brought to 60 degrees Celsius and loaded to failure to record stability and flow.
Step 05
Volumetrics and cores
Bulk and maximum specific gravity are determined, air voids and VMA calculated, and core density is expressed as a percentage of laboratory or maximum density.
What you receive
- Binder content against the job mix formula
- Recovered aggregate grading against the envelope
- Marshall stability and flow
- Air voids, VMA and VFB
- Core density and degree of compaction
- Layer thickness from cores
When this test is the right one
- Acceptance testing of asphalt supplied to site
- Quality control during paving
- Investigating premature rutting, ravelling or cracking
- Verifying compaction of a completed layer
- Resolving a dispute over material supplied
Methods and standards
Every result is reported with its method reference and the calibration status of the instrument used.
ASTM D6927 Marshall stability and flowASTM D2172 quantitative extraction of asphalt binderASTM D2726 bulk specific gravity of compacted mixturesASTM D2041 theoretical maximum specific gravityAASHTO T166 and T209 equivalentsASTM D3549 thickness of compacted specimens
Common questions
What engineers most often ask us about asphalt testing.
Commonly 3 to 5 percent after construction. Below about 3 percent the mix becomes unstable and prone to rutting and bleeding; above about 8 percent it is permeable, which lets water and air in and leads to stripping and ravelling.
Yes, by coring. Cores give in place density, layer thickness and, once broken down, binder content and grading. That is the usual route when a completed pavement is in dispute.
Around 15 to 20 kg of loose mix covers extraction, grading, Marshall and volumetrics with retained material to spare. For cores, three per lot at 100 mm or 150 mm diameter is typical.
Often ordered alongside
Most investigations combine several of these. We scope them together so you are not paying to mobilise twice.
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Read moreNeed asphalt testing on your project?
Send us the location, the structure and your programme. You get a scoped quotation with the standard, the number of tests and the turnaround written into it.