In France, Proctor tests, I-CBR (Immediate California
Bearing Ratio) tests and tensile strength tests are the important
experiments recommended to determine the feasibility
of a specific material to be used in road engineering. The ICBR
index defines the capacity of a material to support the
circulation of building machines, and measures the ratio
of force required for a circular piston to penetrate into a
granular medium in a CBR mould at the speed of 1.27 ±
0.1 mm/min. The prescribed I-CBR values for different
road layers are specified in French standard NF P 98-115
[15]: for a sub-base material – prescribed value of 35%
with a minimum value of 25%; for a base-course material –
prescribed value of 45% with a minimum value of 35%.