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You are here: Home / Research / Testing Facilities and Equipments / Strength and Stiffness Testing System / California Bearing Ratio (CBR)

California Bearing Ratio (CBR)

Description

The California Bearing Ratio (CBR) test was developed by the California state highway department and is widely used to determine the resistance strength of sub-grade and sub-base materials. The test is basically a simple penetration test using a load frame and a standard compacted CBR test mold of the material to be tested. It is a penetration test in which a standard piston, with a diameter of 50 mm (1.969 in), is used to penetrate the soil at a standard rate of 1.25 mm/minute. The results of the test are then compared and evaluated to known standards already established for the material being tested. Application standards are ASTM D1883; AASHTO T193; BS 1377 Part 4.

Testing Ranges

  • Load cell: 10 kN and 50 kN
  • LVDT: 5 mm X 0.001 mm

Material Properties

  • CBR value at soaked condition for base, subbase, and subgrade
  • CBR value at un-soaked condition for base, subbase, and subgrade

Application

  • Evaluation of subgrade strength of roads and pavements
  • CBR value is used with empirical curves to determine the thickness of flexible pavement layers

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