The five-layer Aurivillius type structures with the general chemical formula Bi5Fe2-xMnxTi3O18, where x = 0, 0.6, 1.2 have been synthesized and tested. The SEM studies showed a significant increase in grain size in the manganese-modified Aurivillius type ceramic material (for x = 1.2). The increase in the amount of manganese ions (Mn3+) affects the decrease in the temperature at which the relaxation processes take place. Namely from 525 K (1 kHz) and 725 K (1 MHz) for BFT sample (x = 0) to 355 K (1 kHz) and 565 K (1 MHz) for BFM12T sample (x = 1.2). Using the Arrhenius’s law and the Vogel-Fulcher’s relationship the activation energy (Ea) and the relaxation time have been calculated. The value of Ea increases with the increase of the Mn amount from 0.737 eV (for x = 0) to 0.915 eV (for x = 1.2).
From the construction made in the “white box” technology, first of all tightness is required - on the structural elements there should not be any cracks or scratches, through which water could penetrate, which in consequence may lead to deformation of structural elements and even loosing of their load-bearing capacity. Among the methods enabling the location of weakened places in watertight concrete, the ground penetrating radar (GPR) method is effective because the local occurrence of water in the structure evokes a clear and unambiguous anomaly on the radargram. In addition, the GPR method allows you to indicate places where water flows without the necessity of excluding the object from use and interference in the construction layers. The designation of such locations will make it possible to undertake technical activities that can facilitate the takeover of water and thus ensure the desired load-bearing capacity and usability of the object. Using the GPR method, you can also designate places that have already been deformed – discontinuities or breaking. The article presents a case study of investigations that determine the causes of leakage of tunnels made in the “white box” technology in: twice within the bottom slab of the tunnel (1 GHz air-coupled and 400 MHz ground-coupled antenna) and once in the case of tunnel walls (1.6 GHz ground-coupled antenna).