Abstract: A method for compacting a concrete mix in a casting mold into which the concrete mix is poured between at least two opposite and approximately parallel mold walls. The opposite mold walls are moved in a push-pull manner and essentially on the plane of the walls so that the concrete mix is subjected by the frictional action from the mold walls to an internal compacting shear produced by contradirectional movement of the opposite mold walls.

Abstract: A ram casting machine for the fabrication of concrete slabs which is movable on a casting bed. The machine incorporates a feed hopper and a concrete flow channel with ram numbers cyclically reciprocated therein in opposite directions for generating internal pressure in the cast concrete. Each ram member including at least one wedge-shaped surface assembly having first and second inclined annular surfaces, with the entrance to the concrete flow channel and having a steeper inclination than the second inclined annular surface.

Abstract: An extruder for the fabrication of concrete slabs, especially hollow-cored slabs, movable on a casting bed and incorporating a feed hopper or similar, at least one feeder, especially an auger, for generating internal pressure in the cast concrete, and at least one coring member or similar, for generating the desired slab cross-section.The extruder in accordance with the invention comprises an assembly of at least two wedged surfaces, of which at least one is fitted in conjunction with the coring member, and the space between the surfaces is continuously changing due to a cyclic longitudinal movement, generating inside the space a compacting shear action in the concrete mix.