C.B.R test is abbreviation of California Bearing Ratio test. The test was developed by The California State Highways Department, California USA in 1930. It is developed to evaluate the mechanical strength of road structures. The road structures are defined as subgrades, lower subbase and upper subbase. Subgrade material is referred to soils, sand for lower subbase, whilst crusher run for upper subbase.
Generally the test performed is either Laboratory Test or Insitu CBR Test (on site). The test should be carried out in accordance with BS 1377. The good CBR value for road structrures is more than 5%. For value less than 3% is considered as poor material or Unsuitable Material (USM). During construction of road or pavement structures, samples existing subgrades shall be taken for test. If the value is less than 5%, the existing subgrade shall be removed at certain depth and replaced with suitable materials.
Generally the test performed is either Laboratory Test or Insitu CBR Test (on site). The test should be carried out in accordance with BS 1377. The good CBR value for road structrures is more than 5%. For value less than 3% is considered as poor material or Unsuitable Material (USM). During construction of road or pavement structures, samples existing subgrades shall be taken for test. If the value is less than 5%, the existing subgrade shall be removed at certain depth and replaced with suitable materials.
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