Abstract: A slip-form machine (220) for laying of a second concrete slab (120) of a sleeperless rail-bed including a locomotion mechanism (222, 232) adapted to provide axial translation of the machine along a first slab (110); a slip-form (370) adapted to receive concrete exiting a discharge port (336) via a rearward exit (340) and form an uncured second concrete slab (120) during the axial translation; and a height adjustment mechanism (360) operable to adjust a height of a cover (350) of a forward exit (338) with respect to the first concrete slab (110).