Tsallis entropy modeling of Pressure Stimulated Currents when cement-based materials are subjected to abrupt repetitive bending loadings

Abstract

Pressure Stimulated Currents (PSCs) are emitted while brittle materials of high electrical resistivity are subjected to mechanical loading. The PSCs are related to the generation of cracks and the consequent evolution of cracks’ network in the bulk of the specimen. In the experimental protocol described here cement-mortar beams of rectangular cross-section were subjected to Three-Point Bending (3PB) repetitive loading/unloading loops. The qualitative and quantitative characteristics of the recorded PSCs match corresponding recordings previously published. More specifically, during the load increase a spike-like PSC emission was recorded followed by a relaxation of the PSC, after reaching its final value. The relaxation process of the PSC was then studied in terms of non-extensive statistical physics (NESP) based on Tsallis entropy equation. The behavior of the Tsallis parameter was studied in relaxation PSCs in order to investigate its potential use as an index for monitoring the crack evolution process with a potential use in non-destructive laboratory testing of cement-based specimens of unknown internal damage level. This analysis of the experimental data indicated that the value of the entropic index q exhibits a characteristic decrease attaining the critical value of 1.25 while reaching the ultimate strength of the specimen, and thus could be used as a forerunner of the expected failure.