Radio-wave-reflecting Concrete for Lateral Guidance in Automatic Highways

A method for producing radio-wave-reflecting concrete, which is potentially useful for lateral guidance in automatic highways, is provided. In the form of cement paste, it contains a small amount (0.5 vol.%) of 0.1 mm diameter carbon filaments as an admixture. The radiation absorbed is negligible compared to that reflected. The reflectivity at 1 GHz is 10 dB higher for radiowave-reflecting cement paste compared to conventional cement paste. With the filaments, the reflectivity is 29 dB higher than the transmissivity. Without the filaments, the reflectivity is 3–11 dB lower than the transmissivity. The addition of the filaments not only provides the ability to reflect electromagnetic radiation, it also reinforces the cement paste under tension, especially if the filaments have been treated with ozone prior to incorporation in the paste. © 1998 Elsevier Science Ltd