Abstract

A plasma arc can be employed to demolish a concrete structure at a high efficiency, while preventing a secondary problem due to noise, flying dust and chips, and the like. The concrete structure can be demolished by melting a surface of the concrete structure by generating a plasma arc from a plasma torch (15) of a plasma arc generator, mixing thermite powder (T) with a supply gas (Gc) for the plasma torch (15), directing the plasma arc at the surface of the concrete structure, and controlling the rate of supply of the thermite powder (T) to the plasma torch (15) in response to the operation of the plasma arc, including initiating and stopping the supply of the thermite powder (T) to the plasma torch (15) in a manner coordinated with the initiation and stoppage of the plasma arc, thereby controlling the heat generated by the thermite reaction, and melting the surface of the concrete structure. The plasma generator (1) can be provided with a feeder (20) for mixing the thermite powder (T) with the supply gas (Gc), and controller (30) for controlling the rate of supply of the thermite powder (T) or for stopping the supply of the thermite powder (T).