»Porous Asphalt«-Channels

This type of slot unit is one of our latest developments. Porous asphalt is also known as self-draining asphalt or "whisper concrete". These names indicate the two main advantages: Reduction of aquaplaning and significantly lower noise impact on the environment. 

This special type of asphalt concrete was developed in the 1980s. Its composition is characterised by a large fraction of coarse mineral aggregate, which results in large contiguous voids. Rainwater can pass downwards through these voids. A bitumen seal prevents water from draining into the subsoil or body of the road. The surface water is drained to the side by the sideward camber of the road. It is necessary to install special drainage channels, the porous asphalt channels, to ensure the water is safely and reliably drained from the side of the road. 

Special feature: The porous asphalt channel has inlet openings in the side facing the carriageway at the level of the draining bitumen layer. The percolated rainwater passes through these holes and into the drainage system. 

Supplementary requirements:

  • Drainage of un-percolated water through surface slot
  • Resistance to de-icing salt, as porous asphalt coatings tend to frost faster