The removal of concrete layers from biological shields by microwaves
Concrete blocks reinforced with steel bars have been subjected to microwave attack at a frequency of 896 MHz at power levels up to 25 kW. The surface concrete has been explosively removed to the depth of the reinforcement, 10 cm, at a rate of about 2 litres per kWh. Heating was localised around the point of attack, with temperatures up to 300 C at the fractured face being attained. A simple mathematical model of the propagation and absorption of microwaves was used to estimate the temperature rise of concrete at microwave frequencies of 896 and 2450 MHz, at different power levels with and without the presence of reinforcing bars. This demonstrated that reinforcement is expected to increase significantly the temperature rise in the concrete between the irradiated surface and the reinforcement, and that near-surface heating should be more rapid at the higher frequency. There was reasonable agreement between predicted and observed temperatures at the higher power levels. Further desk and laboratory studies are proposed before proceeding to a full-scale practical demolition machine. The requirements for a prototype remotely operated demonstration system have been identified. This consists of a static generator of high power (at least 50 kW) transmitting microwaves via a steerable waveguide to a remote applicator mounted on a simple three-axis manipulator capable of traversing realistically large concrete test panels.
Bibliographic Reference: EUR 12185 EN (1989) FS, 42 pp., ECU 5
ISBN: ISBN 92-825-9998-1;CD-NA-
Record Number: 198910927 / Last updated on: 1994-12-01
Original language: en
Available languages: en