TheR-Value test^[1] measures the response of a compacted sample ofsoil oraggregate to a vertically applied pressure under specific conditions. This test is used byCaltrans forpavement design, replacing theCalifornia bearing ratio test. Many other agencies have adopted the California pavement design method, and specify R-Value testing for subgrade soils and road aggregates.

The test method states:

The R-value of a material is determined when the material is in a state of saturation such that water will be exuded from the compacted test specimen when a 16.8 kN load (2.07 MPa) is applied. Since it is not always possible to prepare a test specimen that will exude water at the specified load, it is necessary to test a series of specimens prepared at different moisture contents.

R-Value is used in pavement design, with the thickness of each layer dependent on the R-value of the layer below and the expected level oftraffic loading, expressed as aTraffic Index. Details of the pavement design procedure are given inChapter 600 of the California Highway Design Manual.

• Tests in geotechnical laboratories
• Pavement engineering

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