3.3.6 Strain Alleviating Membrane (SAM)
A strain alleviating membrane (SAM) is a sprayed seal consisting of a binder containing a heavily modified PMB (Figure 3.9). SAMs are used to treat cracked pavements by alleviating the effects of mechanical strains that occur in a road pavement, and thereby reduce the risk of reflection cracking at the surface.
The concept of a SAM seal is to provide a relatively thick membrane of a robust binder that absorbs movement from a weak or cracked underlying layer. SAMs are generally not effective if used with smaller aggregates as the binder layer is too thin to effectively absorb the strain. The use of larger aggregates of 10 mm or larger is recommended.