Shrinkable core for forming hollow precast load bearing wall panels

A mold arrangement (300) for precasting load bearing wall panels, the mold arrangement (300) comprising:

• I. a shrinkable core (100) for inserting in a mold cavity (200), the shrinkable core (100) having:
• A. a first wall (110) and a second wall (120) being spaced from each other by a first distance (d1) to define an internal region (115) in-between;
• B. a first side element (112) and a second side element (122) arranged to close opposite edge portions of the spaced first wall (110) and second wall (120) such that fluid concrete cannot pass the opposite edge portions to get into the internal region (115), the first side element (112) and second side element (122) being spaced by a second distance (d2);
• and
• C. a spacing element (130) configured to vary at least one of the first distance (d1) and the second distance (d2) such that a circumference along the first and second walls (110, 120) and the first and second side elements (112, 122) shrinks monotonically with lowering said at least one distance;
• II. a first outer wall (210) and a second outer wall (220) being arranged oppositely to each other;
• and
• III. a first outer side wall (212) and a second outer side wall (222) being arranged opposite to each other and combined with the first and second outer wall (210, 220) to form a mold cavity (200) there-between;
• wherein the shrinkable core (100) is arranged in the mold cavity (200) such that the first and second wall (110, 120) are arranged in parallel to the first and second outer wall (210, 220);
• wherein at least one of the first and second outer side walls (212, 222) has a protrusion (231) which extends in the mold (200) and is configured to get into contact with at least one of the first and second side elements (112, 122) of the shrinkable core (100) when the shrinkable core (100) is inserted in the mold (200) such that after casting the load bearing wall panel with a cavity formed by the shrinkable core (100), the cavity comprises a further opening perpendicular to two openings along the lateral extending of the shrinkable core (100);
• and
• wherein the outer side wall (212) has further projections (250) extending from a bottom part to a top of the first outer side wall (212), and the second outer side wall (222) comprises further grooves (240) extending from a bottom part (610) to a top of the second side wall (222), wherein the further projections (250) and the further grooves (240) are configured to cast grooves and projections at the side parts of the precast load bearing wall panel which are adapted to engage with each other when connecting the precast walls with each other.