Lesson 5/Learning Event 2
ADVANTAGES AND DISADVANTAGES OF THE CBR TEST
Advantages
The test can be performed by personnel with relatively little experience and training.
The test is correlated to service behavior and construction methods and has been successfully
used for many years.
The CBR method adapts more quickly to airfield pavement design for immediate use than any
other method.
You can test soil with simple, portable equipment.
You can run tests in either the field or the laboratory for design, construction control, or
evaluation of existing construction.
The test is primarily intended for subgrades but applicable to a wide range of different materials.
Testing can be done on samples representative of future water conditions.
Disadvantages
The laboratory and field compaction methods are not identical. However, comparative tests
indicate that reasonable correlation of results can be obtained from field compact materials and
samples compacted under similar conditions in the laboratory.
Because added strength to highly stabilized surfaces such as asphaltic concrete is neglected, the
assumption of a completely saturated subgrade condition sometimes results in a too conservative
factor of safety.
Because many of the procedures are of an arbitrary nature, you must run the test to exact
standards in order for the design tables to be valid.
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