The problem of wet-cast concrete products getting stuck or being uncontrollably ejected from a flexible mold during demolding is solved by moving the flexible mold through a passage, defined by both a mold-receiving surface and a rotatable mold-support distanced therefrom, while moving an edge of the flexible mold along an unsmooth path that includes at least one sharp point.

The problem of wet-cast concrete products getting stuck or being uncontrollably ejected from a flexible mold during demolding is solved by moving the flexible mold through a passage, defined by both a mold-receiving surface and a rotatable mold-support distanced therefrom, while moving an edge of the flexible mold along an unsmooth path that includes at least one sharp point.

The problem of wet-cast concrete products getting stuck in a flexible mold during demolding is solved, prior to demolding the wet-cast concrete products, by removing a vacuum on the flexible mold by moving at least one side edge of the flexible mold away from a part of the flexible mold that is adjacent to the at least one side edge in a direction opposite the open side of the flexible mold.

The problem of wet-cast concrete products getting stuck in a flexible mold during demolding is solved, prior to demolding the wet-cast concrete products, by removing a vacuum on the flexible mold by moving at least one side edge of the flexible mold away from a part of the flexible mold that is adjacent to the at least one side edge in a direction opposite the open side of the flexible mold.

A system for the automatic release of cast concrete products from flexible and deformable moulds is described. The system has an apparatus configured to supply the moulds and carry out the pre-mould-release of the products contained within such moulds. The apparatus has a first conveyor belt associated with a first pre-mould-release group and a second conveyor belt associated with a second pre-mould-release group. The second conveyor belt is placed downstream of the first conveyor belt and both pre-mould-release groups are configured to facilitate the subsequent mould-release of the products. The system further has a mould-release machine arranged downstream with respect to the first and second conveyor belts. The mould-release machine has a mould-release group, configured to carry out the extraction of the products from the respective moulds, and a plurality of conveyor belts, configured to move the moulds and the products inside the mould-release machine.

A mold part (6) for manufacturing vertical joints of keystones (5) comprising a foam piece (7); and a silicone piece (11) covering the foam piece (11), wherein the foam piece (7) and the silicone piece comprise a plurality of protrusions (17) and recesses (16), thus providing a toothed surface in a concrete surface of the vertical joint. The mold-part can comprise stiffeners (20) and handles (19, 21) for demolding manually after curing the concrete keystones, leaving the inner surface of the keystone with a toothed appearance.