RADIO WAVE ABSORBING BODY

PROBLEM TO BE SOLVED: To adjust radio wave absorbing power by providing holes at particular intervals in a radio wave absorbing body, inserting carbon fiber bundles with particular cross section and volumetric specific electric resistance coefficient. SOLUTION: A carbon fiber bundle 3 is made by aligning many long carbon fiber placed in parallel and bonded with a bonding agent; its cross sectional area is 0.2 to 80mm , volumetric specific electric resistance coefficient is 10 to 10 Ω.cm, preferably 10 to 10 Ω.cm. A hole 2 is located near the surface of concrete 5 constituting a dielectric layer, and is provided along the interface between a surface board 1 and concrete 5. Also, the hole 2 has an arrangement interval of 10 to 500mm and formed by embedding a synthetic resin pipe as required. Next, a fiber bundle 3 in inserted to the hole 2 thereby forming a radio wave absorbing layer and, behind it, reinforcing bars 4 constituting several number of radio wave reflecting layer are arranged with concrete 5 placed between them. By doing this, in response to the request at the place of use, the number of fiber bundle 3 to be inserted to holes 2 is increased or reduced so that the radio wave absorbing characteristics can be adjusted.