Schematic representation of the experimental apparatus. 

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... has been established that the application of mechanical stress on rock or cement-based materials changes its electrical and dielectric properties, as a consequence of microscopic structural changes [1-4]. A macroscopic indication of such kind of changes is the observation of transient weak electrical currents which are produced when the samples are subjected to stress loads up to failure [ 5, 6, 7, 8, 9]. The correlation of the electrical properties of rocks to their mechanical changes has attracted the interest of many researchers not only due to the theoretical significance itself, but also due to its high practical importance. The above correlation may serve as a non-destructive testing method for 415 the verification and quantification of mechanical damages which are introduced to solid samples, in conjunction with other diagnostic tools. In this sense, Broadband Dielectric Spectroscopy (BDS) technique can provide information about dynamical structural changes of materials which are subjected to mechanical stress by means of the changes of their dielectric properties which are recorded over a wide frequency range. So, in the present work the complex dielectric permittivity İ * of marble samples was recorded over a wide frequency range, during the application of uniaxial stress loads to the samples, up to failure. Different types of data representation are used for the analysis of experimental data, in order to reveal the correlation of dielectric properties with the applied load. Dielectric spectroscopy measurements were carried out by means of a high-resolution broadband spectrometer (Novocontrol Alpha-N Analyzer). The frequency range of the applied ac electric field was between 10 -2 Hz and 10 6 Hz. The specimen was mounted between two parallel stainless-steel electrodes forming a sample capacitor. The electrodes were electrically isolated from the load platens by thin teflon plates. Good electromagnetic shielding was implemented to the whole sample holder in order to diminish noise problems that are common especially at low frequencies. The stress was recorded continuously with a load cell placed at the bottom side of the capacitor. The experimental apparatus is shown schematically in Fig. 1. Marble samples (Dionysos), collected from Penteli Mt., Attica, were cut in cylindrical shape (2-3 o mm height and 37mm diameter) and dried in an oven at 105 C for one day. Their chemical composition is 98% calcite and 0.2% of quartz and other minerals such as muscovite, sericite and chlorite [10]. Its density is 2.7 Mg/m 3 , its porosity is 0.37% and its absorption coefficient by weight is 0.11%. Conductive silver paint was applied at both sides of the sample, in order to achieve good electrical contact with the stainless-steel electrodes. The marble sample placed between the round plate electrodes of the capacitor can be considered as an equivalent electrical circuit comprised of a capacitance, C( Ȧ ), in parallel with a resistance, R( Ȧ ). These values which are the output of the analyzer are associated to the complex impedance Z * ( Z ) and dielectric permittivity H * ( Z ) through the following ...