Subgrade and foundation layers

The strength of the subgrade is expressed in CBR or stiffness modulus, and from this, the foundation thickness is determined for the foundation class chosen to be used. Out of the four classes established, foundation class 1 cannot be used for rigid pavements and bound foundation class 2 can be used only upon approval of the overseeing organisation. 

The foundation classes and the foundation design procedure are the same as those in flexible pavements and are outlined in Section 13.5.3. 

The separation membrane used in jointed slabs is omitted from CRCP/CRCB construction in order to give a higher level of friction between the concrete slab and the sub-base. 

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