LimsPulse
Construction materials testing

California Bearing Ratio (CBR) Test Apparatus

A load frame that pushes a 50 mm plunger into a compacted soil specimen at 1.25 mm/min and compares the load needed with that for a standard crushed stone. The ratio (CBR) is used to design road and pavement thickness.

  • Road and highway construction
  • Geotechnical testing
  • Airports and railways
  • Construction materials testing
  • Academic labs
Illustration of California Bearing Ratio (CBR) Test Apparatus
Follow your site SOP
This is a typical operating sequence for learning. Your instrument model and approved SOP take precedence.
STAGE 1

Before you start

  1. 1Check the load ring and penetration rate verification is in date and note the ring constant.
  2. 2Check the plunger is clean and undamaged.
  3. 3Prepare the specimen at the target density and moisture and soak it if required.
  • Do not exceed the proving ring's capacity; choose a ring suited to the expected load.
STAGE 2

Setting up

  1. 1Drain the soaked specimen for about 15 minutes, keeping the surcharge on.
  2. 2Place the mould on the frame with the surcharge weights.
  3. 3Seat the plunger with a small seating load, then set the load and penetration gauges to zero.
STAGE 3

Penetration test

  1. 1Start the motor at 1.25 mm/min.
  2. 2Read the load at each standard penetration up to 12.5 mm.
  3. 3Stop the motor and lower the mould.
  4. 4Take a moisture sample from the top 30 mm of the specimen.
  • Keep hands clear of the plunger and mould during loading.
STAGE 4

After testing

  1. 1Convert dial readings to load using the ring constant.
  2. 2Plot load against penetration, correct the origin if needed, and calculate CBR at 2.5 and 5.0 mm.
  3. 3Clean the mould, plunger and spacer disc.
In LimsPulse · Calibration Management

Keep every CBR apparatus in control: usage logs, calibration and maintenance schedules, and automatic blocking of overdue instruments.

See how