Duct unit e.g. cover plate, has contact surfaces that are flat and exhibiting ridges or slots, which interrupt maximum twenty percentage of contact surfaces, where duct unit is made up of concrete and ceramic compound

摘要

The unit has contact surfaces (13) that are flat and exhibiting ridges or slots. The ridges/slots interrupt maximum 20 percentage of the surfaces. The ridges are arranged in the corners of the upper contact surfaces. The ridges are conical in shape and are arranged transverse to a wall thickness of the unit. The unit is made up of concrete, concrete polymer composite, ceramic compound, plastic and reinforcing steel connections. An independent claim is also included for a method for manufacturing a pit unit.