To make it possible to prevent the generation of cracks or voids by leaving a peripheral edge slightly on the rear surface of a PC board and constructing a concrete product construction foundation PC board on which a normal temperature hardened elastic body is laminated, on a crushed stone layer and forcing the board to follow an uneven surface.
A polyurethane-based normal temperature hardened elastic body 2 is laminated on the whole surface with an uniform thickness except for a peripheral edge which is slightly left over on one surface of a PC board which forms a joint comprising a projected part 3 and recessed part 4 on the end in the longitudinal direction, thereby forming a foundation PC board. The foundation PC boards are constructed on the crushed stone layer consolidated on an excavated ground with the normal temperature hardened elastic body 2 placed downward while they are being jointed with the uneven joint of the PC board. The normal temperature hardened elastic body 2 follows with the uneven or undulated areas on the crushed stone and buries the cavity, thereby supporting the layer PC boards elastically. At that time, the normal temperature hardened elastic body 2, while being subjected to deformation, is pushed and extended toward the peripheral edge but it is not extended to the outside of the peripheral edge. This construction makes it possible to lay concrete products on the top of the PC boards lined up horizontally.
YANAKA HISAYUKI
KOBAYASHI KEIICHI
