D27...please explain a bit more about what you want. Are you looking for an acceptable CBR value for each of the courses? If so, that will depend on what your pavement design requires. As an example, if you need a certain structural number, you can achieve that with various combinations of subgrade, subbase, base and surface course layer coefficients. Each of those will have a corresponding CBR value, except for the surface course. Generally, a pavement is built from the bottom up. The subgrade is strong because of its high thickness, even though a lower CBR is used in the subgrade. Each layer is correspondingly similar.
@ Ron, so you're saying there are no standard specification for CBR values for those materials, specs shall be base as per project pavement requirements?
certain agencies may have standard requirements for minimum CBR. otherwise it is the pavement designers responsibility to design the pavement structural section.
