Prefabricated concrete floor structure

A method for forming at least a portion of a precast insulated concrete floor panel having a deck and a plurality of spaced-apart stems extending along the length of the floor panel from the deck, the method comprising the steps of:

• cutting a plurality of stem mold segments from a larger block of expanded polystyrene foam insulation, the multiple stem mold segments being cut from the same block of foam insulation, the stem mold segments being cut in an interlocking pattern from the block of foam insulation, each stem mold segment having a generally “U” shaped cross section having a pair of spaced-apart legs and a web between the legs, the interlocking pattern being formed by the legs of two stem mold segments being cut from between the legs of a third stem mold segment;
• providing a mold, the mold comprising the plurality of elongate stem mold segments extending parallel with one another on respective longitudinal axes in a length direction and being spaced apart laterally adjacent one another in a width direction perpendicular to the length direction, each pair of adjacent stem mold segments having outer surfaces adjacent to one another that define a space therebetween having the shape of the stem to be formed between the pair of adjacent stem mold segments, each mold segment being an integral one-piece foam insulation member formed without seams or joints that extend in the length direction;
• and
• pouring concrete into the spaces between the stem mold segments.