Material Testing · Soil & Pavement Laboratory
CBR Laboratory Equipment
CBR laboratory equipment is the set of moulds, surcharge weights, load frame, proving ring, dial gauges and swell apparatus used to carry out the California Bearing Ratio (CBR) test, the standard laboratory measure of how well a compacted soil or gravel resists penetration, and the basis of pavement layer design and road-material classification in South Africa.
Ecotao supplies a complete CBR set-up, from the 34-T0090 mould to the CTM-01 motorised test machine, to road, geotechnical and university laboratories across South Africa and neighbouring countries.
- SANS 3001-GR40
- TMH1 Method A8
- ASTM D1883 / AASHTO T193
- BS 1377 / EN 13286-47
- Delivery across Southern Africa
Related Ecotao pages
- What is CBR?
- Equipment
- Test procedure
- How to choose
- Standards compared
- South African requirements
- FAQ
- Contact
What is the California Bearing Ratio (CBR) test?
The California Bearing Ratio is a penetration test that compares the strength of a compacted soil, gravel or crushed stone with that of a standard high-quality crushed-stone material. A cylindrical piston is pushed into the specimen at a constant rate, and the force needed to reach set penetrations (2.54 mm and 5.08 mm) is expressed as a percentage of the force the standard material needs at the same penetrations.
A CBR of 100% means the material is as strong as the reference crushed stone. Subgrade clays often test below 10%, while good natural gravels for base and subbase layers test far higher. Because the test is usually done on soaked specimens at several compaction densities, it shows both how strong a material is and how much strength it loses when wet. That is why pavement designers, road authorities and material laboratories rely on it.
Standard reference loads (ASTM D1883 / AASHTO T193)
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| Penetration | Standard unit load | Standard force on a 3 in² (1 935 mm²) piston |
|---|---|---|
| 2.54 mm (0.1 in) | 6.9 MPa (1 000 psi) | approx. 13.3 kN |
| 5.08 mm (0.2 in) | 10.3 MPa (1 500 psi) | approx. 20.0 kN |
The higher of the two ratios is normally reported. Where the 5.08 mm value is higher, the standards require it to be confirmed before it is used.
CBR laboratory equipment supplied by Ecotao
The items below make up a complete laboratory CBR station, grouped by the stage of the test they are used in. Order individual items to complete an existing lab, or ask for a full set-up quotation.
1. Moulds and specimen preparation
These parts hold the soil while it is compacted, soaked and tested. Mould dimensions control specimen volume, so they need to match the method your laboratory follows.
CBR Mould with Collar & Perforated Base
Code 34-T0090
The plated-steel CBR mould is where each specimen is compacted, soaked and penetrated. The removable collar provides compaction headroom and is taken off before trimming. The perforated base plate lets water reach the underside of the specimen during the soak, so the material is saturated through its full height rather than only from the top. Labs testing at three compaction efforts normally keep at least three moulds per sample.
- Internal diameter152.4 mm (6 in)
- Body height177.8 mm (7 in)
- Supplied withCollar, perforated base
- MaterialPlated steel
Solid Base Plate & Surcharge Weights
Codes 34-T0097 · 34-T0094 · 34-T0095
The solid base plate (34-T0097) replaces the perforated base for compaction and unsoaked testing. The annular surcharge (34-T0094) and slotted surcharge (34-T0095) sit on the specimen to reproduce the weight of the pavement layers that will be built above it in service. The annular weight lets the piston pass through its centre during penetration. The slotted weight can be slipped on or off around the swell-plate stem without disturbing the dial gauge. Add enough weights to match the overburden your design specifies.
- Annular surcharge2.27 kg
- Slotted surcharge2.27 kg
- Base plateSolid, fits 34-T0090
Spacer Disc with T-Handle
Code 34-T0091 · 61.4 mm, 50 mm or 36 mm
The spacer disc sits in the bottom of the mould during compaction to set the height of the finished specimen. With the 61.4 mm disc in the 177.8 mm mould, the specimen is 116.4 mm high. That leaves a fixed gap for the surcharge weights and the swell plate once the mould is inverted. The T-handle lets the disc be lifted out cleanly without disturbing the compacted soil. Ecotao lists the disc in three heights, so tell us which method you follow and we will confirm the right one.
- Heights listed61.4 mm, 50 mm, 36 mm
- Diameter (61.4 mm disc)150.8 mm
- HandleRemovable T-handle
Hydraulic Universal Extruder
Code 16-T0080
A hand-pumped hydraulic jack pushes compacted specimens out of their moulds in one smooth stroke. This avoids the cracking and disturbance caused by hammering or scraping material out. After a CBR test the specimen can be extruded intact for moisture-content sampling at the penetration zone. The same frame also takes Proctor and Marshall moulds, so one extruder serves the soil and asphalt sides of the lab.
- DriveHydraulic hand pump
- SpecimensCBR, Proctor, Marshall
2. Loading and measurement
The load frame drives the piston into the specimen at a constant rate while the proving ring and dial gauge record force against penetration. These readings produce the load–penetration curve that the CBR value is calculated from.
Motorised CBR Test Machine
Model CTM-01
The CTM-01 is a two-column CBR load frame with an adjustable upper beam, a proving ring, a penetration bar and a motor-driven loading plate. The motor raises the mould against the fixed piston at a constant speed, so readings are repeatable from operator to operator, unlike hand-cranked frames. It tests soils and mixed materials with a particle size below 40 mm. That suits South African practice, where SANS 3001-GR40 scalps CBR material on the 37.5 mm sieve. The mould and dial gauges are ordered separately.
- Capacity30 kN or 50 kN
- Load speed1.0 mm/min (datasheet)
- Penetration rod50 mm end diameter
- Platen stroke50 mm
- Mould accepted152 mm × 177.8 mm
- Power380 V, 50 Hz, 150 W (three-phase)
- Size / mass34 × 50 × 88 cm, 82 kg
If your method calls for a 1.27 mm/min penetration rate (ASTM D1883), ask Ecotao to confirm the speed setting before ordering.
Proving Ring 50 kN
50 kN · 0.01 mm dial
A proving ring is a precision steel ring that deflects in proportion to the load on it. A dial inside the ring measures that deflection in 0.01 mm divisions, and the ring's calibration factor converts each reading to kilonewtons. A 50 kN ring covers the full range of a 50 kN frame, so stiff crushed-stone and stabilised materials can be tested without overloading the ring. Have the ring calibrated at intervals set by your laboratory's quality system.
- Capacity50 kN
- Dial resolution0.01 mm
- FitsCTM-01 load frame
CBR Penetration Piston
For the CBR load frame
The penetration piston transfers load from the proving ring into the specimen through the centre of the annular surcharge. It must be seated with a small initial load before the gauges are zeroed. This closes any gap at the surface, so the first readings measure soil resistance rather than seating. Careful seating gives a cleaner load–penetration curve and reduces the need to correct a concave-upward start.
- UsePenetration stage
- Works withAnnular surcharge 34-T0094
Dial Gauge 25 mm × 0.01 mm
25 mm travel · 0.01 mm graduation
A CBR station needs at least two dial gauges. One measures piston penetration against the load frame, and one per mould records swell on the tripod during soaking. Readings are taken at fixed penetration intervals up to and beyond 5.08 mm. A 25 mm travel covers the full penetration stage and all but the most expansive clays during the swell stage. The 0.01 mm graduation gives the resolution the calculation needs.
- Travel25 mm
- Graduation0.01 mm
- Used forPenetration and swell
Magnetic Base Dial Gauge Holder
Switchable magnetic base
The magnetic base clamps to the steel load frame and holds the penetration dial gauge rigidly on an articulated arm, so the gauge can be positioned against the mould without drilling or extra brackets. Switch the magnet off to reposition it between tests. A rigid holder matters because any movement of the gauge during loading appears as false penetration in the results.
- MountingSwitchable magnet
- HoldsPenetration dial gauge
3. Soaking and swell measurement
Soaking puts each specimen into the wettest condition it is likely to meet under a road. Swell readings show how much expansive clay a material contains, which is a design concern in its own right.
Swell Tripod, Swell Plate & Soaking Tank
Codes 34-T0093 · 34-T0092/A · soaking tank
The swell plate (34-T0092/A) is a perforated aluminium plate with an adjustable stem that rests on the specimen under the surcharge weights. The tripod (34-T0093) stands on the rim of the mould and holds a dial gauge against the stem. As the soil absorbs water and expands, the stem rises and the gauge records the movement. Swell is reported as a percentage of the initial specimen height. The soaking tank holds the moulds fully immersed, typically for four days (96 hours), so water enters through the perforated base and the top surface. Order one tripod and plate set per mould you soak at the same time, and size the tank for at least three moulds with tripods standing on them.
- Swell plateAluminium, adjustable stem
- TripodSits on mould rim
- GaugeDial gauge, ordered separately
- Typical soak4 days (96 h)
- Tank capacityAsk Ecotao
4. Field companion: Dynamic Cone Penetrometer
Laboratory CBR approves the material. The DCP checks what was actually built on site, layer by layer, without digging test pits.
Dynamic Cone Penetrometer (DCP)
1 m unit with tip and bag
The DCP drives a hardened 60° cone into the ground with an 8 kg hammer dropped 575 mm. The penetration per blow is recorded continuously with depth. Changes in that rate show where pavement layers change and how thick each one is. Established correlations (Van Vuuren 1969, Kleyn and Van Heerden 1983, Smith and Pratt 1983) convert the rate to an estimated in-situ CBR for comparison with design specifications. A test takes a few minutes and reaches about 850 mm, or up to a recommended 2 m with extension shafts.
- Hammer / drop8 kg / 575 mm
- Cone60°, 20 mm base
- Standard depthapprox. 850 mm
- Supplied as1 m, 1 tip, bag (1 m extension separate)
How a laboratory CBR test works, step by step
This overview shows where each piece of equipment is used. Always follow the full method your laboratory is accredited for (SANS 3001-GR40, TMH1 A8, ASTM D1883 or BS 1377-4).
- Prepare the sampleDetermine maximum dry density and optimum moisture content (SANS 3001-GR30 in South Africa), then scalp and mix the material to the required moisture.
- Compact into the mouldPlace the spacer disc in the 34-T0090 mould on its base, fit the collar and compact the soil in layers. Specimens are usually made at several compaction efforts to cover a density range.
- Invert and fit the surchargeRemove the collar and spacer disc, trim the surface, invert the mould onto the perforated base, and add the swell plate and surcharge weights.
- Soak and measure swellStand the tripod and dial gauge on the mould, take a zero reading and immerse it in the soaking tank, typically for four days. Record the final swell before draining.
- Penetrate the specimenSet the mould on the CTM-01 with the surcharge in place, seat the penetration piston, zero the proving ring and dial gauge, and load at a constant rate.
- Calculate and reportPlot load against penetration, correct the start of the curve if needed, read the forces at 2.54 mm and 5.08 mm and calculate CBR. Extrude the specimen with the 16-T0080 for moisture content.
How to choose CBR laboratory equipment
Use these decision points to put together the right CBR station for your laboratory's workload and test method.
- Match the mould to your method. The 34-T0090 mould (152.4 mm × 177.8 mm) suits SANS, TMH1 and ASTM/AASHTO-type methods with a 61.4 mm spacer disc. BS 1377 uses a shorter 127 mm mould without a spacer. Confirm your method before ordering.
- Count moulds by throughput, not by test. Each sample tested at three compaction efforts ties up three moulds for at least four days of soaking. A lab running several samples a week needs moulds, swell plates and tripods in multiples of three.
- Choose load capacity by material. Subgrade soils rarely approach 30 kN, but good crushed stone and stabilised materials can. A 50 kN frame with a 50 kN proving ring covers the full range of road materials.
- Check your power supply. The CTM-01 datasheet lists a 380 V three-phase supply. Plan a three-phase point beside the machine before delivery.
- Plan for calibration. Proving rings and dial gauges need periodic calibration for accredited testing. Budget for the downtime, or keep a spare ring.
- Add a DCP for field verification. If your lab also supports construction control, a DCP lets technicians check layer strength on site and compare it with the lab CBR results.
CBR standards compared: ASTM / AASHTO vs BS 1377
Equipment from different traditions is not always interchangeable. The table shows the main differences that affect what you buy. South Africa's SANS 3001-GR40 and the older TMH1 Method A8 follow the 152.4 mm-mould tradition. Check the current edition of your method for exact requirements.
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| Parameter | ASTM D1883 / AASHTO T193 | BS 1377-4 / EN 13286-47 tradition |
|---|---|---|
| Mould | 152.4 mm ID × 177.8 mm, with 61.4 mm spacer disc | 152 mm ID × 127 mm, no spacer |
| Penetration rate | 1.27 mm/min | 1 mm/min |
| Reading points | 2.54 mm and 5.08 mm | 2.5 mm and 5.0 mm |
| Standard force | approx. 13.3 kN and 20.0 kN | 13.2 kN and 20.0 kN |
| Surcharge units | 2.27 kg (5 lb) weights | 2 kg weights |
| Typical soak | 4 days (96 h) | Commonly 4 days |
The CTM-01 manufacturer lists BS 1377, EN 13286-47, ASTM D1883 and AASHTO T193 as the standards the machine is designed for.
CBR testing in South Africa
In South Africa, CBR results classify natural gravels and soils for road layers under the TRH14 material classes (G1 to G10). CBR is tested to SANS 3001-GR40, with density and moisture from SANS 3001-GR30. Many older contract documents still reference TMH1 Method A8, so most laboratories need to be able to run both.
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| TRH14 class | Density for CBR | Minimum CBR |
|---|---|---|
| G4 | 98% of maximum dry density | > 80% |
| G5 | 95% of maximum dry density | > 45% |
| G6 | 95% of maximum dry density | > 25% |
Source: South African Pavement Engineering Manual, Chapter 3. Project specifications and road authorities may set different limits, so always check the contract documents.
Oversize material: SANS 3001-GR40 scalps CBR material on the 37.5 mm sieve and discards the oversize. The older TMH1 preparation sieved on 19.0 mm and lightly crushed the retained fraction. The CTM-01 is designed for particles below 40 mm, which suits the current method.
- Wet-season design: Soaked CBR matters most in the winter-rainfall Western Cape and in summer-rainfall areas with expansive clays such as Gauteng and KwaZulu-Natal, where saturated subgrades control pavement design.
- Power: plan a three-phase supply for the CTM-01 motorised frame.
- Delivery: supplied from Cape Town throughout South Africa and to Namibia, Botswana, Zimbabwe, Mozambique, Lesotho and Eswatini.
CBR laboratory equipment: frequently asked questions
What equipment do I need for a laboratory CBR test?
A complete laboratory CBR set-up needs a CBR mould with collar and base plate, a spacer disc, annular and slotted surcharge weights, a compaction rammer, a soaking tank, a swell plate with tripod and dial gauge, a CBR load frame with proving ring or load cell, a penetration piston, a penetration dial gauge on a holder, and an extruder to remove the specimen. Ecotao supplies everything on this list apart from the compaction rammer and balances, which can be quoted on request.
How is the California Bearing Ratio calculated?
CBR is the force needed to push the penetration piston into the specimen at a set penetration, divided by the force needed for the same penetration into a standard crushed-stone material, expressed as a percentage. Under ASTM D1883 and AASHTO T193 the standard pressures are 6.9 MPa at 2.54 mm and 10.3 MPa at 5.08 mm. The higher of the two ratios is normally reported, after the 5.08 mm result is confirmed by a repeat test where required.
Which standard is used for the CBR test in South Africa?
South African laboratories use SANS 3001-GR40 for the California Bearing Ratio, with maximum dry density and optimum moisture content from SANS 3001-GR30. The older TMH1 Method A8 is still referenced on legacy contracts. SANS 3001-GR40 scalps material on the 37.5 mm sieve, whereas the older TMH1 preparation worked on the 19 mm sieve with light crushing of the retained fraction.
What size is a CBR mould?
The CBR mould supplied by Ecotao (34-T0090) is 152.4 mm (6 in) internal diameter with a 177.8 mm (7 in) body height, used with a 61.4 mm spacer disc to give a 116.4 mm specimen. British Standard moulds are a different size, 152 mm internal diameter by 127 mm high, so check which method your laboratory follows before ordering.
Why are CBR specimens soaked?
Soaking simulates the wettest condition a pavement layer is likely to experience in service. Specimens are typically immersed for four days (96 hours) under surcharge weights, and a dial gauge on a tripod records swell. The soaked CBR is usually the design value because most road materials lose strength when saturated.
What is the difference between a lab CBR test and a DCP test?
A laboratory CBR test measures the bearing strength of a prepared, compacted and usually soaked specimen at controlled density and moisture, and is used for material classification and pavement design. A Dynamic Cone Penetrometer measures in-situ penetration resistance layer by layer in the field in a few minutes, and its results are converted to an estimated CBR through published correlations. Many projects use both: lab CBR to approve materials and DCP to check what was built.
What CBR values do South African road materials need?
Under the TRH14 classification, as summarised in the South African Pavement Engineering Manual, G4 material needs a CBR above 80 at 98% of maximum dry density, G5 above 45 at 95% and G6 above 25 at 95%. Always check the project specification, since design manuals and road authorities can set different limits.
What power supply does the CTM-01 CBR machine need?
The manufacturer's datasheet for the CTM-01 lists a 380 V, 50 Hz, 150 W supply, which is a three-phase connection. Confirm that your laboratory has a three-phase point near the machine, or ask Ecotao about alternatives before ordering.
Does Ecotao deliver CBR equipment outside Cape Town?
Yes. Ecotao supplies CBR laboratory equipment from Cape Town to laboratories throughout South Africa and to Namibia, Botswana, Zimbabwe, Mozambique, Lesotho and Eswatini. Contact sales@ecotao.co.za or +27 21 911 5835 for a quotation.
Equip your CBR laboratory
Tell us which method you test to and how many samples you run each week. We'll quote a matched set of moulds, surcharges, swell apparatus and a load frame, delivered anywhere in South Africa or neighbouring countries.
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