INVESTIGATION OF DIELECTRIC-PROPERTIES OF BRICK MATERIALS AS A FUNCTION OF MOISTURE AND SALT CONTENT USING A MICROWAVE IMPULSE TECHNIQUE ATVERY HIGH-FREQUENCIES

A pulsed microwave method using a frequency range of about 7 GHz has b een developed based on the principle of the pulsed radar method. This method is employed for the non-destructive quantitative determination of the moisture content and distribution in brickwork. The measurement s are more precise than previous measurements that have used frequenci es below 1 GHz. Owing to the shorter wavelength and the higher absorpt ion coefficient of water in this frequency region, both real and imagi nary parts of the complex dielectric properties are measured with a hi gher accuracy. The expected non-linear relationship between the dielec tric properties of several building materials and their moisture conte nt and salt concentration (NaCl) requires calibration measurements. Th erefore, systematic measurements on brick material, like sand-lime bri ck, solid brick, hollow brick and porous concrete, have been carried o ut. The results are demonstrated and compared with actual theoretical models. (C) 1998 Elsevier Science Ltd. All rights reserved.