Inexpensive, crack-bridging membrane constructions such as SAMI layers (Stress Absorbing Membrane Interlayer) are now being considered for the maintenance of roads, which make it possible to avoid a necessary major overhaul or at least to delay it for a number of years. The SAMI layer is applied to a heavily cracked base and is intended to keep the asphalt layer applied from a subsequent superstructure free of penetrating cracks.

SAMI layers are made with special binders, eg Liesen SAMI Spezial Bitumen. The subsequent superstructure (covering layer) is also mainly carried out with the addition of polymer-modified binders. Due to the splitting off, the membrane can be driven on during the construction work. It also has a supportive effect on the transfer of shear forces between the old and new top layer. The Sami layer is impermeable to water, so the surface water that penetrates through the top layer (e.g. OPA covering) is channeled through the Sami layer.

The new top layer is then applied to the SAMI layer produced in this way using a finisher. The membrane is melted again by the heat and the rolling of the mixed material and part of the highly elastomeric binder is pushed slightly upwards into the lowest area of the new top layer, as a result of which the cavities in this part are completely filled. This zone is now able to absorb tensile stress.

Advantage:
The SAMI layer allows the new top layer to move in relation to the old covering. The new top layer is therefore not forced to absorb stresses that would lead to reflection cracks or fatigue cracks. At the same time, the roadway is sealed and the ingress of surface water is completely prevented. Both layers are permanently bonded