Effect of water content on microwave dielectric properties of building materials

Abstract This paper presents measurement results of the complex dielectric permittivity depending on the humidity for a range of materials used in buildings. It covers a whole range from light to heavy materials with different hygroscopic properties and with a special focus on green building materials. Two specific adjustable stripline test devices of different lengths have been designed and used to perform the extractions of the permittivity from S-parameters measurements using the two transmission lines method. The study covers a frequency band extending from 500 MHz to 2.5 GHz and is carried out on dry, ambient and wet conditioned samples. The main trends are physically discussed, and phenomenological explanations based on the impedance matching and the water absorption among others are proposed for the observed behaviors. The use of the obtained data is illustrated through the extraction of the electromagnetic behavior of a realistic wall.