Road works

California bearing ratio (CBR).  A simple test that compares the bearing capacity of a material with that of a well-graded crushed stone (thus, a high quality crushed stone material should have a CBR 100%).  CBR is basically a measure of strength.  It is primarily intended for, but not limited to, evaluating the strength of cohesive materials having maximum particle sizes less than 0.75 inches (AASHTO, 2000).  It was developed by the California Division of Highways around 1930 and was subsequently adopted by numerous states, counties, U.S. federal agencies and internationally.  Most agency and commercial geotechnical laboratories in the U.S. are equipped to perform CBR tests.

Resistance value (R-Value).  A test that expresses a material's resistance to deformation as a function of the ratio of transmitted lateral pressure to applied vertical pressure.  It is essentially a modified triaxial compression test.  Materials tested are assigned an R-value. The testing apparatus used in the R-value test is called a stabilometer and is identical to the one used in Hveem HMA mix design.  The R-Value is basically a measure of stiffness.

Resilient modulus (MR).  A test used to estimate elastic modulus (a material's stress-strain relationship).  The resilient modulus test applies a repeated axial cyclic stress of fixed magnitude, load duration and cyclic duration to a cylindrical test specimen.  While the specimen is subjected to this dynamic cyclic stress, it is also subjected to a static confining stress provided by a triaxial pressure chamber.  It is essentially a cyclic version of a triaxial compression test; the cyclic load application is thought to more accurately simulate actual traffic loading.  Resilient modulus is basically a measure of stiffness.

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