CBR test press and Marshall
5,000 kgf (50 kN) press for the CBR (California Bearing Ratio) test of soils and the Marshall test of asphalt mixtures, which also performs the consolidation test. Manual and electric automatic models.
The Biopdi CBR / Marshall test press performs the CBR test, the California Bearing Ratio of soils per ABNT NBR 9895:2025 (the Brazilian CBR test standard) and DNIT 172/2016-ME (a method of Brazil's National Department of Transport Infrastructure), and the Marshall test of asphalt mixtures per DNIT 447/2024-ME, just by changing the fixture. The electric automatic version has a capacity of 5,000 kgf (50 kN), electromechanical ball screw drive, speed from 0.001 to 50 mm/min, displacement measurement by encoder with 0.001 mm resolution, load cell, LVDT and touchscreen.
The same press performs the consolidation test per NBR 16853:2020 (the Brazilian consolidation test standard), with the 2" and 3" consolidation cells; for several simultaneous consolidation tests, see the consolidation press. There are two models: the manual CBR press and the electric automatic CBR / Marshall press.
The CBR test measures the resistance of compacted soil to penetration by a piston and is the basis of pavement design for roads and highways; the Marshall test measures the stability and flow of asphalt concrete. The step-by-step procedure for each test is in our articles on the CBR test, the Marshall test and the consolidation test.
Models: manual and electric automatic
Both accept the CBR and Marshall fixtures; the consolidation test is performed on the electric automatic model.
CBR / Marshall Press - Manual
Lever drive, proving ring from 500 to 5,000 kgf (4.9 to 49 kN) and dial indicator. Can be upgraded to a load cell and touchscreen.
CBR / Marshall Press - Electric Automatic
5,000 kgf (50 kN), ball screw, 0.001 to 50 mm/min, 0.001 mm encoder, load cell, LVDT and touchscreen with SD card. Performs CBR, Marshall and consolidation tests.
CBR / Marshall press specifications
Data for the electric automatic version, from the Biopdi manual; the full list is further below.
| Models | Manual and automatic electric |
|---|---|
| Tests | CBR, Marshall and consolidation |
| Capacity | 50 kN (11,240 lbf) |
| Drive (automatic) | Electromechanical, recirculating ball screw; two threaded screws for crosshead adjustment |
| Control (automatic) | Microprocessor with touchscreen, SD card and USB port |
| Test speed | 0.001 to 50 mm/min: 1.27 mm/min for CBR and 50 mm/min for Marshall |
| Actuator stroke | 100 mm, automatic return |
| Displacement measurement | Optical encoder, 0.001 mm resolution; 50 mm LVDT, 0.01 mm resolution |
| Strain channels | Up to 4; two independent, simultaneous LVDT channels (0 to 10 VDC) |
| Load cells | Interchangeable, from 5 kgf (49 N) to 5,000 kgf (49 kN) |
| Data acquisition | CBR at the 14 penetrations of NBR 9895 (0.63 to 12.70 mm); Marshall at 1 Hz; consolidation from 1/8 min to 24 h |
| Distance between columns | 300 mm |
| Dimensions (D × W × H) | 485 × 455 × 1,076 mm |
| Weight | 70 kg (benchtop) |
| Power supply | 220 V, 60 Hz, 540 W |
| Warranty | 12 months against manufacturing defects |
The drawing below, from the press manual, shows the front and side views with the main dimensions of the equipment, in millimeters.
CBR / Marshall press dimensions
Front view: 400 × 75 mm fixed crosshead, 300 mm between columns, actuator with Ø 100 and Ø 80 mm dimensions, 170 × 112 mm touchscreen and a 455.35 mm wide base. Side view: 485 mm depth, 370 mm base height and 1,076.2 mm overall height.
Tests performed on the CBR / Marshall test press
Three tests on the same press, just by changing the fixture.
CBR test (California Bearing Ratio)
ABNT NBR 9895:2025 · DNIT 172/2016-ME · DNER-ME 162/94
Fixture: CBR fixture, load cell and LVDT
Measures the resistance of compacted soil to penetration by the piston, at 1.27 mm/min, and compares it with that of the standard crushed stone at 2.54 and 5.08 mm. The press reads the force at the 14 penetrations of NBR 9895 (the Brazilian CBR test standard), from 0.63 to 12.70 mm. It is the basis of pavement design.
How to perform the CBR testMarshall test
DNIT 447/2024-ME · DNER-ME 107/94
Fixture: Marshall fixture (4"), load cell and LVDT
Breaks the asphalt mixture specimen by compression along its diameter, at 50 mm/min, and measures the stability (maximum load) and the flow (deformation up to the maximum load). Data are acquired at 1 reading per second.
How to perform the Marshall testConsolidation test
ABNT NBR 16853:2020
Fixture: 2" or 3" consolidation cell and LVDT
Loads the laterally confined soil and records settlement over time, at 1/8, 1/4, 1/2, 1, 2, 4, 8, 15 and 30 min and 1, 2, 4, 8 and 24 h. On the screen, the operator sets the maximum force, the time and the displacement limit.
How to perform the consolidation testThe Biopdi automatic electric CBR / Marshall test press runs the CBR, Marshall and consolidation tests automatically, based on the settings entered on the equipment's touchscreen. A microprocessor controls the test and acquires the data for analysis and reporting; the tests are saved to the SD card, which can be read on a computer.
For the CBR, Marshall and consolidation tests, Biopdi supplies fixtures, load cells, extensometers and LVDTs.
Standards met
The CBR / Marshall test press meets the following standards:
For other standards, get in contato our technical team.
Biopdi has its own technology to develop, manufacture and sell any type of soil testing equipment, so any machine parameter can be customized for our customers. Get in contato to learn more.
Videos
Videos of the automatic electric CBR / Marshall test press, showing the main features of the equipment.
Features: manual version
The manual CBR / Marshall test press has a proving ring available in several capacities (500 to 5,000 kgf, 4.9 to 49 kN), lever operation, a dial indicator to measure specimen displacement, and rubber feet.
The manual CBR / Marshall test press accepts the CBR fixture and the Marshall fixture and can be upgraded to a load cell and touchscreen.
CBR test fixture
Marshall test fixture
Features: automatic electric version
The automatic electric CBR / Marshall test press is electromechanically driven: a recirculating ball screw moves the actuator and applies the load, while two threaded lead screws adjust the height and lock the crosshead. Force is measured by an interchangeable load cell (5 to 5,000 kgf, 0.049 to 49 kN), actuator displacement by an optical encoder with 0.001 mm resolution, and specimen deformation by an LVDT. The panel has an on/off switch and an emergency stop button, and the touchscreen controls and sets up the CBR, Marshall and consolidation tests.
On the screen, the operator selects the test, sets the speed and the automatic stop by force or by displacement, follows the graph and saves the result to the SD card.
CBR test
Marshall test
The two drawings below, taken from the operating manual, identify the parts of the press: at the front, the frame and the controls; at the back, the connection and power panels.
Components: front view and front panel
From top to bottom: the fixed crosshead, mounted on the two threaded lead screws that adjust its height; the load cell, which measures the force; the CBR rod and penetration piston; the LVDT, which measures the penetration of the piston into the test specimen; and the actuator, which is raised by the ball screw and applies the load. The front panel has the on/off switch and the emergency stop button, which stops the actuator immediately. The nameplate shows the serial number.
Rear view: connection panel and power panel
The connection panel links the press to the sensors: four DB9 connectors for extensometers and LVDT, the load cell connector (female DB9) and the 8-pin Mike connector, which connects the machine to the electronic controller. The power panel has the two-pole circuit breaker, which protects the equipment against overload on both phases, and the three-pin power cord connector. At the bottom are the cooling vents and the anti-vibration feet.
Touchscreen
The Biopdi automatic electric CBR / Marshall test press has a touchscreen that handles all test settings. Tests are run directly on the screen, which saves them to an SD memory card for later use on a desktop or laptop; the USB port is used for parameter setup and control.
Two screens from the current version, taken from the manual: test selection, which already includes consolidation, and the test screen with each control labeled.
Test selection
After the adjustments, the operator taps the test: CBR, Marshall or consolidation. Each button opens the test setup: speed and automatic stop at maximum force or maximum displacement for CBR and Marshall; maximum force, time and displacement limit for consolidation.
Test screen
The force (kgf) versus position (mm) graph is plotted during the test, with the actuator force and position read in real time on the right. Below are the pause, stop and start controls; next to them, cancel test and return to the home screen.
Main touchscreen functions
Settings screen
- Tare: zeroes position and force
- Position (mm) and force readout
- Start position: returns to the zero point
- Actuator up and down arrows
Configuration screen
- Upper and lower limit switches
- Emergency stop activated indicator
- Load cell limit indicator
- Transducer: shows whether a load cell is connected
Test setup
- Test selection: CBR, Marshall or consolidation
- CBR and Marshall: name, speed, automatic stop at maximum force or maximum displacement
- Consolidation: name, maximum force (kgf), maximum time and displacement limit
Test screen
- Graph plotted during the test
- Real-time force and position readout
- Start, pause, stop and cancel the test
- Saving to SD card
Technical specifications: automatic electric
Technical specifications of the automatic electric CBR / Marshall test press.
Load cells
Load cells available for the automatic electric CBR / Marshall test press.
Fixtures and accessories
Fixtures and accessories used with the CBR / Marshall test press.
LVDT (displacement transducer)
Linear displacement transducer that measures penetration in the CBR test, flow in the Marshall test and settlement in the consolidation test.
Load Cell
Measures the force applied to the test specimen. Interchangeable, from 5 to 5,000 kgf (0.049 to 49 kN), chosen according to the load expected in the test.
Marshall testing head
Made of 1045 steel with corrosion protection, with upper and lower rings for the 4" specimen, loaded along its diameter.
CBR apparatus
All brass: mold with collar and perforated base plate, perforated swell plate, two M8 rods with wing nuts and tripod for the dial gauge.
The drawings from the fixture manuals show each part separately and the external dimensions. Neither fixture is bolted to the press: just place it on the platen and center it.
CBR fixture: parts
From bottom to top: perforated base plate, spacer disc, cylindrical body (mold) with clamps, collar, perforated plate with stem, annular disc and the extensometer tripod, which measures swell. The two M8 rods with wing nuts clamp the assembly together. After the swell stage, the tripod, the annular disc and the plate are removed; the piston is brought into contact with the soil, the LVDT is adjusted and penetration begins.
CBR fixture: dimensions
Side view and top view, assembled with the rods and tripod: 396 mm high and 240 mm in diameter at the base. Made entirely of brass.
Marshall fixture: parts
The 4" test specimen lies on its side between the lower ring and the upper ring, and the load is applied along the diameter. The two guide pins project from the lower plate; the upper plate, held by screws, secures the specimen in the fixture. Made of steel with corrosion protection.
Marshall test head: dimensions
Side, top and front views: 177 mm high, Ø 200 mm base, and ring dimensions of 126 mm in the top view and 76 mm in the front view.
2" and 3" consolidation cells
Rigid base, ring that holds the test specimen, porous stones and rigid loading cap, with the option of submerging the sample. Mounted on the automatic electric CBR / Marshall test press for the consolidation test. See also the consolidation press.
Marshall test molding accessories
The test specimen that the press breaks in the Marshall test comes from the mold and the hammer. Biopdi supplies all three molding accessories, which you can order with the press or separately:
Marshall hammer
Compaction hammer that drops in free fall onto the asphalt mixture in the mold. The standard requires a mass of 4,540 g and a drop height of 457.2 mm, with 50 or 75 blows per face, depending on the traffic level.
Marshall mold
4-inch steel cylinder (101.6 mm inside diameter), with collar and base plate, that gives the test specimen the 63.5 mm height required by DNIT 447/2024-ME (the Brazilian highway agency's Marshall test method).
Marshall compactor
Applies the hammer blows mechanically, at 64 ± 4 per minute, onto the compaction pedestal. It removes operator variability and speeds up molding of the five binder contents in the mix design.
The step-by-step procedure for molding and testing is in the article on the Marshall test. Request the accessories in the quote, stating the standard and the number of blows.
Frequently asked questions
The most frequently asked questions about the CBR and Marshall test press.
What is a CBR test press used for?
The CBR press performs the California Bearing Ratio (CBR) test, which measures the resistance of compacted soil to penetration by a piston and is used to design the pavement of roads and highways. The result compares the pressure in the soil with that of a standard crushed stone at penetrations of 2.54 mm and 5.08 mm, per ABNT NBR 9895:2025 (the Brazilian CBR test standard).
Does the same press perform both the CBR test and the Marshall test?
Yes. The CBR / Marshall press changes fixtures: the CBR fixture, with the penetration piston, for the CBR test, and the Marshall fixture, with the breaking head for the 4" specimen, to break the asphalt mixture in the Marshall test. Both Biopdi models, the manual and the electric automatic, accept both fixtures.
Does the CBR / Marshall press perform the consolidation test?
Yes, the electric automatic version does. The Biopdi manual calls it the CBR, Marshall and consolidation press: with the 2" or 3" consolidation cell, it applies the force set on the screen and records settlement at the reading times of NBR 16853:2020 (the Brazilian standard for the one-dimensional consolidation test), from 1/8 min to 24 h. For laboratories that run several consolidation tests at the same time, Biopdi also offers a dedicated consolidation press.
What is the speed of the automatic CBR press?
From 0.001 to 50 mm/min, programmed on the touchscreen. The range covers the 1.27 mm/min penetration rate of the CBR test and the (50 ± 5) mm/min of the Marshall test. Displacement is measured by an optical encoder with 0.001 mm resolution.
What is the difference between the manual and the automatic CBR press?
On the manual press, the operator applies the load with the lever and reads the force on the proving ring and the deformation on the dial indicator. On the electric automatic press, the motor-driven ball screw applies the speed programmed on the touchscreen, the load cell reads the force, the encoder and the LVDT read the displacement, and the screen plots the graph and saves the test to the SD card.
What is the current standard for the Marshall test?
DNIT 447/2024-ME (a test method of DNIT, Brazil's National Department of Transport Infrastructure), which replaced DNER-ME 043/95 for hot asphalt mixtures. For cold mixtures, DNER-ME 107/94 applies. The CBR test follows ABNT NBR 9895:2025 and, at DNIT, DNIT 172/2016-ME (non-reworked samples) and DNER-ME 162/94 (reworked samples).
How is CBR calculated?
CBR is the pressure measured in the soil divided by the standard pressure, as a percentage: 6.90 MPa at 2.54 mm penetration and 10.35 MPa at 5.08 mm. The higher of the two values is used, after correcting the curve if it is concave at the start. The step-by-step procedure, with a worked example, is in the article on the CBR test.
Does Biopdi supply the Marshall test accessories?
Yes: Marshall hammer, mold and compactor, in addition to the press's CBR and Marshall fixtures, load cells and LVDT. Request them together with the press in your quote, stating the standard and the number of blows.
Other soil testing equipment
See also our other soil testing equipment and the articles on the direct shear, the triaxial test and the resilient modulus.
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