To structurally prevent the falling of collapsed concrete as small and medium-sized lumps when a concrete structure spontaneously collapses.

One or more pieces of short and minute reinforcing wires are adhered to every particle of crushed stones used as coarse aggregate for concrete. A required amount of the resulting crushed stones with reinforcing wires are mixed with a ready mixed-concrete to form a concrete in which minute reinforcing wires are uniformly distributed. When the concrete collapses, since small lumps are joined and supported by minute reinforcing wires to be able to prevent them falling, the secondary disaster is prevented.